Long Lin

NO reduction reaction (NORR) is not only an attractive method for sustainable ammonia (NH3) production, but also a green method to eliminate the harmful gas NO. But a few NORR catalysts have been explored at present, and it remains a great challenge to explore efficient catalysts for the conversion of NO to NH3. Here, based on first-principles calculations, we proposed a g-C3N4-based biatomic catalyst (BAC) as a promising candidate for NORR. We systematically studied the activation and conversion of NO on g-C3N4 loaded with double 3d transition metal (TM), 3d TM and non-metallic atom, double non-metallic atoms. After screening for structural stability, adsorption of NO, catalytic activity of NORR and selectivity of NH3, it is found that 2Mn@g-C3N4 is a stable NORR catalyst with high catalytic activity and selectivity. And then studied the charge variation to understand in depth the mechanism of its high …

Based on density functional theory (DFT), the adsorption properties of ZrSe2 monolayer modified by transition metals (Fe, Co and Ni) to NO2 and SO2 of two harmful gases are predicted in this paper. The calculation results indicate that ZrSe2 monolayer modified by metal atom loading is more stable than that doped by metal atom. Therefore, the adsorption behavior of ZrSe2 modified by metal atom loading on two harmful gases is studied. The results demonstrate that the adsorption energy of ZrSe2 monolayer loaded with metal atoms can be significantly improved the adsorption energy of the system, and the chemical bond and charge transfer between metal atoms and gas molecules are generated, indicating a strong interaction between metal atoms and gas. Besides, NO2 gas adsorption on a substrate loaded with metal atoms is superior than that of SO2 gas. The Ni-ZrSe2 system is suitable for NO2 gas sensor …

Lithium-ion batteries are found in every corner of our lives, and safety concerns have received significant attention. Therefore, monitoring thermal runaway gases from lithium-ion batteries is crucial for human safety. In this paper, density functional theory (DFT) is used to establish the adsorption models of Cu-decorated HfS2 (Cu@HfS2) and Cu-embedded HfS2 (Cu-HfS2), taking C2H4, CH4, H2, CO and CO2 as target gases. By calculating the adsorption energy, charge transfer, charge differential density, energy band, density of states, work function, sensing response, and recovery time, it is found that Cu@HfS2 has a strong adsorption effect on C2H4, CO and H2, and Cu-HfS2 has a better adsorption effect on CH4 and CO2. At room temperature, the chemisorption of CO by Cu-HfS2 is stable, the sensing response is better, and the desorption time is shorter, so it has the potential to be used as a resistive gas sensor …

Single atom catalysts (SACs) have been in the forefront of catalysts research because of their high efficiency and low cost and provide new ideas for development of renewable energy conversion and storage technologies. However, the relationship between the intrinsic properties of materials such as lattice thermal conductivity and catalysis remains to be explored. In this work, the lattice thermal conductivity of BN and graphene was calculated by ShengBTE. In addition, the adsorption properties of 3d-TM (TM = V, Cr, Mn, Fe, Co, Ni) on BN and graphene were investigated using first-principles methods, and it was found that Ni atom can form relatively stable SACs compared to other TMs. The molecular dynamics (MD) simulation and migration barrier of Ni loaded on BN and graphene were calculated. Our study found that graphene has higher thermal conductivity and is easier to form SACs than BN, but the SACs …

Nitrogen fixation using electrochemical methods on the surface of single-atom catalysts (SACs) provides a highly feasible strategy for green and low-energy-consumption ammonia (NH3) production. Herein, using density functional theory (DFT) calculations, we explored in detail the potential of monolayer BC3N2 SACs supported with 3d transition metal (TM) atoms (TM@BC3N2) to facilitate nitrogen reduction. The results revealed that the TM@BC3N2 systems exhibited remarkable catalytic activity in the nitrogen-reduction reaction (NRR). The fine NRR activity was related to the just-right bonding/antibonding orbital interactions between the 2π* of N2 and the d orbitals of the TM ions. The nitrogen-adsorption configurations were found to have different activation mechanisms. In addition, the effects of convectively formed convex nitrogen defects (VN) on the interaction between N2 and VN-TM@BC3N2 and the NRR …

In recent years, two-dimensional TMDs materials have been proved to be high-performance gas sensor materials. Janus material is a member of the TMD family, and its gas sensing performance research is particularly important. Gas sensing mechanism of toxic gases on transition metal dichalcogenides based Janus MoSeTe monolayers is investigated using the density functional theory. Six transition metals are considered to modify the MoSeTe surface, by comparing the adsorption energies of the transition metal on both sides of the MoSeTe monolayer, it is found that the transition metal doping is more stable on the Se side. The MoSeTe surface is activated by transition metal modification, and the gas behavior is improved by transition metal modification, it is found that Ir-MoSeTe had the best sensing performance for NO2, Os-MoSeTe had the best sensing performance for CO, and Ru-MoSeTe had the best …

Developing efficient, economical and environmentally friendly multifunctional electrocatalysts is a prerequisite for developing renewable energy conversion and storage technologies. Dual-atom catalysts have significant catalytic performance compared to monoatomic catalysts due to the larger metal loading and synergistic effects between metal atoms, and the reduction of overpotentials and increase of the reaction rate are the keys to obtaining high-performance OER/ORR bifunctional electrocatalysts, as determined by the electrocatalytic thermodynamics and kinetics of electrocatalysis. This work investigates efficient electrocatalysts with bifunctional catalytic activity for OER/ORR. Modifying the MoTe2 material by doping with transition metal atoms shows that the catalysts exhibit better electrochemical stability due to higher solvation potentials. The Pd2@MoTe2 catalysts were screened for bifunctional …

The development of oxygen reduction reaction (ORR) electrocatalysts with high activity, high stability and low-cost is still a grand challenge. Transition metal carbides (TMCs)-based catalysts have been reported as one species of oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) trifunctional catalyst with high efficient and favorable stability. Particularly, TMCs exhibit excellent ORR activity in electrochemical catalysis, even be profitable comparable with Pt in some situations, but the clarification of the intrinsic catalytic mechanism of VC remains a challenge. Herein, the potential performance of VC system on the ORR by using the first-principles calculation method based on density functional theory and quantum mechanics. The results showed that both end-on and side-on adsorptions on the surface of VC system all possess have satisfactory ORR catalytic …

In this study, DFT calculations are used to analyze the adsorption of industrial waste gases (NO2, SO2, H2S, and NH3) on WSe2 monolayers. The adsorption energy, energy band, density of states, charge transfer, and recovery time of the adsorption structures between the target gas molecules and the Os-doped WSe2 are studied. Compared with pure WSe2 monolayer, Os surface bonding doping WSe2 (Os-modified WSe2) and Os doping with Se vacancy of WSe2 (Os-embedded WSe2) exhibit improved gas molecule adsorption ability. Among them, the adsorption energy of the Os-modified WSe2 monolayer on NO2, SO2, H2S, and NH3 is greater than that of the WSe2 monolayer. At the same time, it is proved that the Os-embedded WSe2 can be used as a gas sensor for H2S and NH3 gas molecules at a high temperature.

The adsorption properties of CH4, H2S, SO2, CO, H2O and NO molecules on transition metal-supported SnSe2 surface are investigated by the first-principles method. The calculation results show that the transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) has the lowest adsorption energy when supporting at the Sn site of SnSe2, indicating the system is relatively stable. Also, we find that CH4, SO2 and H2O molecules tend to adsorb on Sc-supported SnSe2 surface, H2S and NO molecules prefer to adsorb on V-supported SnSe2 surface, while CO molecule and Fe-supported SnSe2 surfaces have strong interaction. And, CH4, H2S and H2O molecules act as donors to provide electrons to the substrate, while SO2, CO and NO molecules act as acceptors to gain electrons from the substrate. An analysis of charge difference density and density of states reveals that the adsorption energies of gas molecules are …

For the detection of the more hazardous nitrogen oxides (NO2), there is a need to find a readily fabricated, low-cost, high-performance two-dimensional material. This paper selected three transition metal disulphides (TMDs), MoTe2, MoSe2 and MoS2, as materials for detecting NO2 molecules by density flooding theory (DFT). The results show that the pure Mo(Te/Se/S)2 monolayer has a poor detection effect on NO2 molecules, and the modified monolayer exhibits better performance than its natural counterpart due to the significant electron hybridization between the dopant and the gas molecules after the introduction of metal atoms on the surface. It also leads to significant changes in electronic properties and work functions. The charge transfer mechanism based on Hirshfeld analysis shows that the charge transfer from the modified substrate to the NO2 molecule improves the binding characteristics. And by …

Building two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) is one of the effective methods to regulate the properties of single 2D materials. In this paper, we stack the hexagonal boron nitride (h-BN) monolayer (ML) on the SnSe2 ML to construct the stable h-BN/SnSe2 vdWH, of which the crystal and electronic structures, together with the optical properties, are also analyzed by the first-principles calculations. The results show that the h-BN/SnSe2 vdWH belongs to a type-I heterostructure with an indirect bandgap of 1.33 eV, in which the valence band maximum and conduction band minimum are both determined by the component SnSe2 ML. Interestingly, the h-BN/SnSe2 vdWH under the tensile strain or electric field undergoes the transitions both from type-I to type-II heterostructure and from the indirect to direct bandgap semiconductor. In addition, the carrier mobility of the h-BN/SnSe2 …

For the detection and monitoring of hazardous gases, for which two-dimensional material gas-sensitive elements have excellent gas-sensitive properties, the adsorption behavior and electrical response to hazardous gases (NO2 and SO2) revealed by MoTe2 monolayers modified by Cun, Agn and Aun (n = 1 to 4) are investigated in this article using first principles. To better simulate the situation under realistic doping, the number of nanoclusters doped ranges from 1–4, while the most stable calculated structure is chosen based on the formation energy. Calculations of the energy band structure, work function, density of states, frontier molecular orbitals and other electronic properties of the adsorbed systems show that the introduction of metal atoms effectively improves the electrical conductivity of the MoTe2 monolayer, with significant improvements for the gas-sensitive response, as well as increasing the adsorption …

Based on the first-principles calculation, the adsorption structure and electronic characteristics of CO, NO2, SO2 and NH3 adsorbed on pure, defective and metal atom doped MoTe2 monolayer were systematically studied. The original MoTe2 monolayer and MoTe2 monolayer containing Te defects can be used as room temperature gas sensors to detect NO2 gas and SO2 gas, and the adsorption effect can steadily increase in the simulated working environment. The adsorption behaviors of Ag, Pd and Rh atoms with different doping methods were studied. The calculation results show that the conductivity and chemical activity between metal atoms and gas is improved after doping, resulting in tremendous adsorption energy and charge transfer. Due to the changes in the energy band structure, the density of states, work function and recovery time after adsorption, different doped systems show the potential of high …

Nowadays, detecting the more hazardous sulphur group of gases (H2S, SO2) is increasingly essential, and there is a need to find a readily fabricated, low-cost, high-performance 2D material. This study investigated the selective detection of H2S and SO2 by MoSe2 monolayers and Pt-doped MoSe2 monolayers using first-principles calculations. Our results show that the dopant dramatically enhances the activity of the material, creating solid interactions with the material surface and that Pt-doped MoSe2 monolayers have the potential to selectively detect these toxic gases because of their different conductive tendencies. This work provides insights into the potential application of unexplored TMDs as chemically resistant sensors for the detection of poisonous gases, which may be of importance for environmental monitoring and industrial manufacturing.

The adsorption of five small gas molecules (CO, CO2, NO, NO2, and NH3) on transition metal (TM)-modified ZrSe2 monolayers (Au-ZrSe2 and Pt-ZrSe2) are studied based on first principles. The adsorption structure, adsorption energy (Eads), electron transfer (Qt), and density of states (DOS) with intrinsic ZrSe2, Au-ZrSe2, and Pt-ZrSe2 monolayers are discussed, and their sensing performance is evaluated. The results show that the electrical conductivity of ZrSe2 is obviously increased after Au and Pt atom modification. The intrinsic ZrSe2 adsorbs the five kinds of gas molecules weakly, while ZrSe2 modified by the Au or Pt atom improves the adsorption of the gas molecules in different degrees. Au-ZrSe2 has the best adsorption effect on NO2 gas molecules, while Pt-ZrSe2 shows strong sensitivity to CO gas molecules. Moreover, Au-ZrSe2 and Pt-ZrSe2 are of great significance for the adsorption sensing …

This paper reports the adsorption of toxic gases (NO2, SO2, and NH3) on a MoSeTe structure based on first principles. It was found that the gas (NO2, SO2, and NH3) adsorption on a pure MoSeTe monolayer was weak; however, the adsorption performance of these gas molecules on transition-metal-atom-supported MoSeTe monolayers (TM–MoSeTe) was better than that on pure MoSeTe monolayers. In addition, there was more charge transfer between gas molecules and TM–MoSeTe. By comparing the adsorption energy and charge transfer values, the trend of adsorption energy and charge transfer in the adsorption of NO2 and SO2 was determined to be Fe–MoSeTe > Co–MoSeTe > Ni–MoSeTe. For the adsorption of NH3, the effect trend was as follows: Co–MoSeTe > Ni–MoSeTe > Fe–MoSeTe. Finally, by comparing their response times, the better gas sensor was selected. The Ni–MoSeTe system is suitable …

The application of intrinsic and transition metals (TM)-doped VSe2 monolayers for the detection of faulty gases in SF6 electrical insulated equipment is investigated based on first-principles calculations. The electron density difference, density of state, and adsorption energy are analyzed to further clarify the reaction mechanism. The results show that the intrinsic VSe2 monolayer has weak adsorption performance for SO2 and SOF2 molecules, but the adsorption properties of the system are significantly improved after doping TM atoms. Among them, the TM-doped VSe2 monolayer has better sensing performance for SO2 than for SOF2 molecules. Furthermore, the modulating effect of biaxial strain on the gas-sensitive properties of TM-doped VSe2 system is also analyzed. Finally, the recovery time of the gas molecules on the solid adsorbent is evaluated. The results confirm that the TM-doped VSe2 monolayer can be …

NO electrocatalytic reduction (NOER) is an efficient and sustainable way to eliminate NO harmful gas and synthesis NH3. However, finding suitable catalysts for the catalytic reduction of NO to NH3 and improving the catalytic activity of NOER is one of the challenges to be overcome at present. Hence, the potentials of 10 transition-metal (TM) atoms doped in the Pt (1 0 0) surface as efficient and sustainable NOER catalysts are systematically studied by using first-principles calculation. The mechanisms of NOER were explored by calculating the Gibbs free energy. The results showed that Ti/Cr/Co/Ni-Pt has the excellent NOER catalytic activity, and there is better selectivity than hydrogen evolution reaction (HER) for Ti/Co/Ni-Pt systems. According to results of limiting potential, Ni-Pt exhibits high activity and selectivity for NOER towards NH3 synthesis. Furthermore, we also studied the mechanisms of NO conversion to N …

As the main pollutant in the air, NO2 is hugely harmful to the environment and health. It is crucial to develop a room temperature NO2 gas sensor with high response and good selectivity. In this work, S-doped SnO2 was successfully prepared by annealing with SnS nanoparticles as the precursor. S-doped SnO2 showed excellent response to 5 ppm NO2 (10.7), with a fast response (27 s) and recovery times (32 s), and good selectivity at room temperature (RT). The excellent NO2 sensitivity of S-doped SnO2 is attributed to its large specific surface area and large charge transfer between the substrate and NO2. This work can be extended to prepare high-performance NO2 gas sensors by annealing other transition metal dichalcogenides.

The rational design and development of an efficient bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the key to developing new renewable energy storage and conversion technologies. Transition metal nitrides (TMNs) have shown excellent energy storage and electrochemistry potential due to their unique electronic structure and physicochemical properties. In this paper, based on the first-principles method of density functional theory (DFT), a series of efficient and stable bifunctional single-atom catalysts (SACs) were designed on Mo2N by introducing transition metal atoms as active sites, and the effects of different TM atoms on the catalytic performance of 2D-Mo2N (Two dimensional Mo2N) were evaluated. The calculation results show that TM@Mo2N exhibits excellent stability and good conductivity, which is conducive to electron transfer during the …

The electronic structures, magnetic and optical properties of pure ZrSe2, V, Mo mono-doped ZrSe2 (V–ZrSe2, Mo–ZrSe2) and (V, Mo) co-doped ZrSe2 are researched by the first-principles of density functional theory (DFT). The results show that V–ZrSe2 and Mo–ZrSe2 can become magnetism, and the total magnetic moments generated are 1.76 μB and 2.06 μB by V–ZrSe2 and Mo–ZrSe2, respectively. The stable ferromagnetism (FM) properties in (V, Mo) co-doped ZrSe2 are mainly derived from the hybridization of V:3 d, Se:4p and Mo:4 d orbitals. Due to the doping of V and Mo atoms, which improves electric conductivity and makes up the infrared absorption coefficient of pure materials. In addition, we find that biaxial strain changes the electronic structure of (V, Mo) co-doped ZrSe2 monolayer, and the ferromagnetism of the system be changed significantly. In conclusion, (V, Mo) co-doped ZrSe2 magnetic …

In this study, the adsorption of three industrial gases (CO2, NO2 and SO2) on ZrSe2 monolayers with modified transition metal (TM=Y, Zr, Nb, Mo, Rh, Ru, Pd, Ag) are calculated using first-principles methods for possible applications of different TM-ZrSe2 as industrial gas sensors and adsorbents. Studying the density of states (DOS), adsorption energy (Eads), charge transfer (Q), charge difference density (CDD), work function (W) and recovery time of three kinds of gas molecules adsorbed on TM-ZrSe2 monolayers and their sensing performance are evaluated. The findings reveal that CO2 gas molecules are more likely to be adsorbed on Zr-ZrSe2 monolayer, NO2 is apt to be adsorbed on Y-ZrSe2 monolayer, and SO2 gas molecules have stronger adsorption behavior on Zr-ZrSe2 monolayer. The analysis of CDD and DOS shows that the Eads of gas molecules are related to charge transfer and orbital hybridization …

Transition metals modified to enhance the performance of electrocatalytic reduction of carbon dioxide (CO2) has received significant attention. In this work, a novel high-efficiency electrocatalyst Rh-BC3N2 has been constructed and simulated using first-principles calculations to reveal the mechanism of enhanced electrocatalytic reduction of CO2. Our results reveal that Rh atom can be stably supported on top of N site of BC3N2 monolayer. For CO2 activation, CO2 was activated to a bent structure with the bond angle OI-C-OII of 146.0°, resulting of the charge transfer between CO2 molecule and Rh-BC3N2. And for CO2 reduction, the rate-determining step for the formation of CH3OH is *CO hydrogenation into *CHO, and the overpotential for *COOH hydrogenation into HCOOH is 0.23 V. Our work provides a promising candidate for the CO2 reutilization, with valuable insights and an important prototype for future …

Since the oxygen reduction reaction (ORR) is the cathodic reaction of energy storage and conversion devices such as fuel cells and metal–air batteries, the search for catalysts with high-performance toward ORR has become the focus of attention. Transition metal dichalcogenides (TMDs) have the advantages of easy integration, inexpensive, harmless, good stability, and have vast application prospects in stabilizing the single atom. Hence, in this study, we investigated the feasibility of several 4d/5d single transition metals (TM = Rh, Pd, Ag, Ir, Pt, and Au) doped with CrSe2 for ORR electrocatalysis on the basis of density functional theory (DFT) calculations. Our results demonstrated that most of the TM-doped systems are stable, exhibiting metal conductivity, and can well activate the adsorbed O2. Interestingly, compared with end-on adsorption configuration, O2 is more likely to be adsorbed on the catalysts by a side …

With the development of Internet of Things technology, gas sensors are developing towards integration and miniaturization. Therefore, developing NO2 sensors with fast response and low detection limit at low temperatures is of great significance. In this study, we report SnS nanosheets via a simple hydrothermal method with excellent NO2 sensing performance and explore its gas sensing mechanism combined with first-principles calculation. The as-prepared SnS nanosheets exhibited high response (17.6) to 50 ppm NO2, specific selectivity, and fast response/recovery time (16/35 s) at 150 °C. In addition, the theoretical limit of detecting SnS nanosheets to NO2 was 8 ppb, much lower than other NO2 gas sensors. The adsorption of SnS and SnS with oxygen defects on NO2 was analyzed by density functional theory (DFT). It was found that the excellent gas sensing performance of the SnS nanosheets was attributed …

We use GGA and GGA+ U methods to calculate the magnetic and optical properties of pure, Fe doped, Mn doped,(Fe, Mn) co-doped and (Fe, Mn, V S n) co-doped SnS 2 based on first principles. The results show that both Fe doping and Mn doping have spin polarization. The most stable (0, 3) configuration of (Fe, Mn) co-doped SnS 2 exhibits magnetism, which mainly comes from the magnetic coupling between Fe-3d state, Mn-3d state and the nearest neighbor S-3p state of doped atoms. The most stable (0, 3, 1) configuration in (Fe, Mn, V S n) co-doped SnS 2 also exhibits magnetism, which comes from the magnetic coupling between Fe-3d state, Mn-3d state and the nearest neighbor S-3p state of doped atoms. We also find that the introduction of doping atoms enhances the electromagnetic absorption capacity of the ɛ 1 (ω) of the dielectric function and increases the electrical conductivity. Mn doped and (Fe, Mn …

Intrinsic defects and hydrogen play an essential role in regulating photocatalytic properties of semiconductor materials. Bismuth oxychloride (BiOCl) is an important ternary bismuth-based photocatalytic material, for its wide bandgap allows band-gap engineering to tailor its properties. In this paper, we use first-principles to study the effects of intrinsic defects and hydrogen on the electronic structure of BiOCl. We studied the intrinsic defect formation energies, defect electronic structures and the diffusion of these defects in BiOCl. We found that the p-type conductivity and band gap variation in BiOCl may be caused by the Fermi level pinning effect and intrinsic defective states around the band edges. Intrinsic defects of Hint, OCl and BiCl show delocalized features which may have a predominant effect for carrier transfer. As the temperature rises, the diffusion of oxygen vacancies in the xy plane goes up most drastically …

A SnS monolayer is a new two-dimensional material with a black phosphorous structure, with high carrier mobility and a large surface-to-volume ratio, and is an ideal candidate material for gas sensors. The adsorption and sensing behaviors between the SnS monolayer and gas molecules are enhanced under the action of TM atoms with high catalytic performance. The adsorption behavior of CO and H2S on intrinsic and transition metal atom modified SnS monolayers is investigated based on the first principles calculations. The adsorption structure, adsorption energy, electron transfer, density of states, electron local density, work function, and desorption properties are discussed to evaluate the potential applications of SnS monolayers as scavengers and gas sensors for CO and H2S molecules. The results show that Ni, Pd, Pt and Cu atoms tend to be adsorbed on TH sites, while Ag and Au atoms are more easily …

We researched the coadsorption of CO and CH 4 molecule on the most stable structure of metal atom (Ni, Ag, Au, Rh, Zn, Pt) doped SnO 2 (110) surface with the first principle methods. The formation energy results show that the Au/SnO 2 (110) surface is the most stable structure. The adsorption energy, bond length, bond angle, density of states, electron population and charge density difference of gas molecule adsorbed on Au/SnO 2 (110) surface are researched, which shows that Au/SnO 2 (110) surface have excellent adsorption performance to CO and CH 4 molecule. The stable adsorption of double CO on Au/SnO 2 (110) surface shows that it has practical value. The research of CO and CH 4 coadsorption on Au/SnO 2 (110) surface shows that the Au/SnO 2 (110) surface has stronger adsorption properties to CO than CH 4 molecule. Our research indicates that Au/SnO 2 is a potential CO sensor material.

The magnetic and optical properties for double impurities (Fe, Mn) doped SnSe2 are investigated by first principles calculations. We calculate that the magnetic moments of Fe and Mn for Fe and Mn mono-doped SnSe2 are 3.98 μB and 4.97 μB, respectively. In the GGA + U method, the ferromagnetism of the (Fe, Mn) co-doped SnSe2 system prefers the most stable state, which is resulted from the hybridization between Fe:3d, Mn:3d and Se:4p states. In addition, we apply strain to research the magnetism for the (Fe, Mn) co-doped SnSe2 system in the GGA + U method. We find that the structure of molecule are changed by strain and the ferromagnetism of (Fe, Mn) co-doped SnSe2 is also significantly improved. The introduction of transition metal (TM = Fe, Mn) can effectively improve electric conductivity. And the adsorption strength of TM doped SnSe2 is also outstanding enhanced. The deficiency of ultra violet …

Silver niobate (AgNbO3, AN) dielectric ceramics and their antiferroelectric behavior have attracted increasing attention for their potential applications in energy-storage capacitors. However, AN’s inferior dielectric breakdown strength, recoverable energy storage density, and efficiency have limited its application. In this work, a combination of chemical composition design and liquid-phase sintering was considered for the fabrication of highly insulated and desensitized AN-based ceramics for enhancing Eb, Wrec, and η of AN. We design and prepare (1 − x)AgNbO3-x(Sr0.7Bi0.2)HfO3 (AN-100xSBH, x = 0.00–0.06) ceramics with the addition of 1 mol% BaCu(B2O5) (BCB) as a sintering aid to realize this. It is found that highly desensitized ceramics can be formed at 1000–1030 °C over the course of 2 h. The electrical property characterization results indicate that the AFE state and Eb are significantly enhanced with …

Using the first-principles approach, we investigated the electronic and chemical properties of cupric oxide CuO (110) and CuO (111) and substantiated their catalytic activity toward CO oxidation. It is found that CuO (111) surface is more stable than the CuO (110) surface. We firstly study that adsorption of CO and O2 on perfect, oxygen vacancies and Cu-anchored CuO (111) surface. It is found that adsorption of CO and O2 molecules are chemical. Then we selected the most stable adsorption structure of CO/O2 to investigated the CO oxidation mechanism on different surface, here we choose to study the Langmuir–Hinshelwood (LH) mechanism and Eley–Rideal (ER) mechanism. The results show that perfect and Ovacancy CuO (111) surface is more inclined to LH mechanism, while the Cu-anchored CuO (111) surface is more inclined to ER mechanism. The results show that CuO catalyst is very effective for CO …

In this paper, based on density functional theory GGA+ U method, the electronic structure, magnetic and optical properties of single Mn, single Mo and (Mn, Mo) co-doped SnSe 2 are studied. The calculation results show that the doping of single Mn and single Mo can make the intrinsic SnSe 2 magnetic. In addition, five different (Mn, Mo) co-doped configurations are calculated and the∆ E of the stable ferromagnetic configuration is about− 227.6 meV. The stable ferromagnetic configuration is caused by the strong hybridization of the d-p orbitals of Mn, Mo and Se atoms and the formation a Mn: 3d-Se: 4p-Mo: 4d coupling chain. And the absorption intensity of SnSe 2 system in visible light is improved by the introduction of doped atoms. Our study shows that introducing appropriate dopants is a feasible method to improve the magnetic and optical properties of intrinsic SnSe 2 base.

Doping is very effective in regulating the properties of two-dimensional materials. Based on the first principles of density functional theory, the effects of the electronic and magnetic properties on the 1T-HfSe2 monolayer with single doping of non-metallic atoms (NM) and transition metal atoms (TM) and co-doping of metal and non-metallic atoms are systematically studied. We find that N, P and As exhibit non-magnetic metal properties. In contrast, F, Br and I exhibit magnetic semiconductor properties. The F-doped system retains the magnetic semiconductor properties under (−6%–10%) strain, and the band gap varies from 0.131 eV to 1.122 eV. Magnetic moments are generated outside the Ni atom doping system for metal atom doping. For metal and non-metal atoms doping, due to the interaction between TM and NM, found that not only can it produce massive magnetic moment and stimulate the initially did not …

The development of efficient catalysts for NO electrocatalytic reduction (NOER) is an effective way to synthesize ammonia and solve environmental pollutants. Now, Pt, Au and other metal surface electrocatalysts still have great challenges for the practical application of NOER due to their high cost. However, using single-atom catalysts (SACs) of low-cost and high catalytic activity to study NOER is relatively rare. Herein, based on first-principles methods, the catalytic performance of a series of transition metal supported on the pure 1T-SnSe2 monolayer for NOER is systematically studied in this paper. The calculation results show that Sc, Ti, Y, Zr and Hf atoms can stably form SACs on 1T-SnSe2 monolayer, and the N-O bond can be successfully activated when NO is adsorbed. In addition, the Zr supported 1T-SnSe2 monolayer (Zr@SnSe2) has a high catalytic activity for NOER, with a low limiting potential of 0.11 V …

In the present work, we have concentrated on the structural, electronic, and optical properties of single-layer phase MgCl2. When bulk MgCl2 reduces to monolayer form, then it exhibited indirect to direct bandgap transformation. The result indicates that the monolayer MgCl2 exhibits insulating characteristics with a direct bandgap of 7.377 eV whereas its bulk form has an indirect bandgap of 7.02 eV. It means that when reducing the dimensionally of the MgCl2 materials than its bandgap significantly increased. The optical properties of the monolayer MgCl2 have been investigated using DFT within the random phase approximation. The calculated refractive index values are very near to water, which means that monolayer MgCl2 material will be a transparent material. Also, the optical absorption coefficient is found to be very high in the ultraviolet (UV) region. From optical properties, the out-of-plane (E⊥Z) direction of polarizations is shifted towards the higher photon energy as compared to the in-plane (E||X) direction. From the optical properties profile, the polarizations along in-plane and out-of-plane are different therefore it shows anisotropic behavior. These investigated results show the monolayer MgCl2 could be a promising material for optoelectronic nanodevices such as deep UV emitters and detectors, electrical insulators, atomically thin coating materials.

The adsorption behavior of transition metal (TM = Cr, Mn, Fe, Co, and Ni) atoms in VS2 monolayer, and the gas-sensing mechanism of CO in (Cr, Mn, Fe, Co, and Ni)-VS2 monolayer were studied using density functional theory. The results show that the band structures of Cr-, Mn-, Fe-, Co-, Ni-VS2 systems maintain metallic properties. Interestingly, through the analysis of charge transfer and adsorption energies, the (CO adsorption on VS2) CO/VS2 system exhibited physical absorption, while the (CO adsorption on TM-VS2) CO/TM-VS2 system exhibited chemisorption. The results show that there is a strong interaction between TMs-VS2 and CO, and a covalent bond is formed between CO and TMs. In addition, the band structures of CO/ (Cr-, Mn-, Fe-, Co-, Ni-VS2) systems also maintain metallic properties. At the same time, the appropriate adsorption energy and short recovery time at high temperature indicate that …

We have carried out a first-principles study of the adsorption of three types of hazardous gases onto pristine and Pt, Au atom modified HfSe2 monolayer. The adsorption structure, adsorption energy, electron transfer and applied strain of the HfSe2 monolayer were discussed, and their sensing performance was evaluated. The results show that the adsorption energies of the pristine HfSe2 for gas molecules were all small. In contrast, the adsorption energies and charge transfer were improved by the adsorbed of different metal atoms. The best adsorption effect on H2S gas molecules was observed, especially after adsorbing with Au atoms, which showed strong sensing properties for H2S. The effect of applied strain on the Au-HfSe2/H2S adsorption system was also investigated, with the adsorption energy decreased with increased strain. The results indicate that the Au-HfSe2 monolayer was an ideal material sensor …

The adsorption behavior of SF6 characteristic decomposition products (SO2 and SOF2) on intrinsic and transition metal (TM) atom modified SnS monolayers is investigated based on the first principles. The adsorption structure, adsorption energy, density of states, electron localization function, electron density difference, work function, and desorption properties are discussed to evaluate SnS monolayers as potential candidates as adsorbents for SO2 and SOF2. Our results show that the detection performance of the intrinsic SnS monolayer is poor due to the relatively weak interaction with gas molecules. After introducing TM dopants (TM = Pd, Pt, Ag and Au) on SnS monolayer, Pd and Pt atoms tend to be adsorbed on TH sites, while Ag and Au atoms are more easily captured by TS sites. The results of adsorption energy and electronic properties showed that TM atoms could significantly improve the adsorption …

Electrocatalytic N2 reduction reaction (eNRR) and NO electroreduction reaction (NOER) are considered as the effective methods to synthesize NH3 under ambient conditions. Based on density functional theory, a series of transition metal atoms supported P3C sheet is systematically investigated to screen out the most promising catalyst for eNRR and NOER. The results indicate that the W/P3C could be an efficient single atom catalyst for eNRR and NOER with the limit potentials of −0.70 and −0.59 V respectively. Remarkably, W/P3C is more conducive to eNRR and NOER than hydrogen evolution reaction. It can be concluded that the local geometric and electronic structure are altered due to the interaction between metal and support, which could promote eNRR and NOER. We hope this work could provide promising method to design the effective electrocatalyst.

Electrocatalytic reduction is an effective method to remove harmful gas NO. In the process of reduction, NH3, one of the most important chemical raw materials in industrial production, can also be produced. However, large-scale practical application of NO electrocatalytic reduction is still a challenge, and to find the efficient, low-cost and stable catalysts is a problem that needs to be solved at present. By use of density functional theory calculation, we systematically studied that the potential of FeS2 (100) containing S vacancy (S-vacancy FeS2) as catalyst for NO electrocatalytic reduction. Our results revealed that NO can be chemisorbed stably at the S vacancy of FeS2 (100) surface and consequent reduction of NO molecular can generate NH3 and H2O. The S-vacancy FeS2 as catalyst has an excellent electrocatalytic activity of NO under ambient conditions. More interestingly, when the O atom of NO molecule is …

Using the first principle calculation based on density functional theory, the CO adsorption on pure VO 2 monolayer and Pd-loaded VO 2 monolayer (Pd/VO 2) investigated systematically. The electronic structure and properties of the most energetic configuration are analyzed in terms of density of states and charge density difference. The results showed that the adsorption energy of CO on pure VO 2 monolayer was− 0.239 eV, and the length of V–O bond did not change obviously, which indicated physisorption. Further studies showed that the adsorption energy of CO adsorption on Pd/VO 2 surface was− 2.010 eV, and the length of V–O bond changed significantly, indicating that CO can be chemically adsorbed on Pd/VO 2 surface. Finally, the calculation of optical properties showed that the absorption of visible light by CO adsorption on VO 2 monolayer can be substantially improved due to the supported Pd atom …

In this paper, the sensing properties of (Ni, Pd, Au)-embedded VS2 for CO, H2S, NO, NO2 and SO2 gas molecules are investigated using first-principles. The adsorption energies, charge transfer, density of states, band structures, and work functions of five inorganic molecules on Ni-VS2 are estimated. It is clearly pointed out that these five gases are chemically adsorbed on Ni-VS2-ML. The decrease in work function indicates that Ni-VS2-ML is a candidate field effect transistor for (CO, H2S, NO, NO2 and SO2) detection. The properties of the (CO, H2S, NO, NO2 and SO2)/Ni-VS2-ML systems are also investigated under biaxial strain. The results show that applying biaxial strain is an effective strategy to tune the sensing performance of (CO, H2S, NO, NO2 and SO2)/Ni-VS2-ML.

The structure and electronic properties of two-dimensional vertical van der Waals arsenene/SnS2 heterostructure are investigated based on the first-principles calculations. The results show that the arsenene/SnS2 bilayer forms a type-II heterostructure with the indirect band gap of 0.870 eV, which is conducive to separating the photogenerated electron-hole pairs. Importantly, the electronic properties of the arsenene/SnS2 heterostructure can be effectively adjusted by applying an external electric field and biaxial strain. Both compressive and tensile strains can decrease the band gap of the arsenene/SnS2 heterostructure, while compressive strain reduces the band gap faster, and the band alignment will have a transition from type-II to type-I when the tensile strain increases to 8%. The band gap of the arsenene/SnS2 heterostructure changes linearly under the external electric field from -1.0 to 1.0 V/Å, while the type …

By the first-principles calculations, the sensitivity of CO, H2O and NO adsorption on Au doped SnSe2 monolayer surface is investigated. The results show that CO and H2O molecules are physically adsorbed on Au doped SnSe2 monolayer and act as donors to transfer 0.012 e and 0.044 e to the substrate, respectively. However, the NO molecule is chemically adsorbed on substrate and acts as an acceptor to obtain 0.116 e from the substrate. In addition, our results also show that the biaxial strain can effectively improve the adsorption energy and charge transfer of gas molecules adsorbed on the substrate surface. Also, the recovery time of desorbed gas molecules on the substrate surface is calculated, and the results indicate that the Au doped SnSe2 is a perfect sensing material for detection and recovery of CO and NO under −8% strain.

Based on the first principles of the GGA method, the magnetic and optical properties of intrinsic SnS2; Fe, Cr mono-doped SnS2; and (Fe, Cr) co-doped SnS2 are studied. The results show that the ground states of Fe, Cr mono-doped SnS2 are spin polarized, and the magnetic moments caused are 1.99 μB and 3.00 μB, respectively. The magnetic moment of Fe mono-doped SnS2 is mainly produced by Fe:3d orbitals, and the magnetic moment of Cr mono-doped SnS2 is mainly produced by Cr:3d and Sn:4d orbitals. We calculate that in the (Fe, Cr) co-doped SnS2 system, Fe, Cr and the adjacent S atoms form a strong hybrid, that is, the closest S atom between Fe and Cr atoms mediates the spin polarization and ferromagnetic (FM) coupling. This promotes the formation of a Fe:3d–S:3p–Cr:3d coupling chain, so that (Fe, Cr) co-doped SnS2 obtains FM stability. In addition, with the introduction of Fe and Cr atoms, the …

Finding the active sites of suitable metal oxides is a key prerequisite for detecting CH. The purpose of the paper is to investigate the adsorption of CH on intrinsic and oxygen-vacancies CuO (111) and (110) surfaces using density functional theory calculations. The results show that CH has a strong adsorption energy of −0.370 to 0.391 eV at all site on the CuO (110) surface. The adsorption capacity of CH on CuO (111) surface is weak, ranging from −0.156 to −0.325 eV. In the surface containing oxygen vacancies, the adsorption capacity of CuO surface to CH is significantly stronger than that of intrinsic CuO surface. The results indicate that CuO (110) has strong adsorption and charge transfer capacity for CH, which may provide experimental guidance.

Recent advances in the synthesis and characterization techniques of atomic-scale thicknesses of crystals have enabled the fabrication of various two-dimensional lateral heterostructures (LHSs). In this paper, we systematically investigate the geometrical structures, electronic properties, band alignments, and optical properties of phosphorene/arsenene LHSs using first-principles calculations based on density functional theory. First, we constructed four stable phosphorene/arsenene LHSs with different edge contacts, named A–Z, Z–A, A–A and Z–Z phosphorene/arsenene LHSs. We then investigated the electronic structures of the different edge contacts. Interestingly, the calculated electron localization functions show that the most stable six-membered rings and previously reported five-membered and seven-membered rings are formed at the interface of the blue phosphorene/arsenene LHSs. Moreover, the band …

Electrochemical N 2 reduction is a promising method for NH 3 production due to its environmental friendliness. By means of density functional theory, we systematically investigated the potential of Fe-embedded Au (111) monolayer as a candidate of N 2 fixation catalyst. As a thermodynamically stable surface, the Fe-embedded Au (111) shows a high catalytic activity for inert N 2 molecule. The bond NN of N 2 molecule with an end-on configuration is activated due to the interaction among Fe-d z 2, N-s and N-p z orbitals. Then, our calculated results also reveals that the limiting step of N 2 reduction reaction is the first hydrogenation step with the free energy barrier of 0.85 eV. This finding may open a promising method of NH 3 production and contribute to the development of the monolayer two-dimensional metals.

The adsorption and activation of gas molecules are investigated substantially in solid-gas heterogeneous catalysis. Here we investigated the interaction between gas molecules and unique two-dimensional monolayer Au (111) structure using density functional theory. It is found that CO2, H2O, N2 and CH4 molecules are weakly adsorbed on the surface with the adsorption energies between −0.150 and −0.250 eV due to van der Waals interaction. While CO, NO, NO2, and NH3 molecules are adsorbed more stably with the adsorption energies between −0.300 and −0.470 eV. Especially, the bond length of CO is stretched by 0.038 Å and the bond angle of NO2 is obviously enlarged by 10.460°. The activation originates from the rearrangement of molecule orbitals and the orbitals hybridization between the partial orbitals of gas molecules and Au-5d orbitals. The fundamental analyses of adsorption mechanism and …

Calcium hydroxide (lime) treatment and solid-state anaerobic digestion (SSAD) of corn stover (CS) were carried out simultaneously with different lime doses (0, 2, 3.5, and 5%) and feedstock to seed sludge (F/S) ratios (6, 8, and 10). It was found that the addition of 3.5% lime improved CH4 yield from 118 mL/g VS to 182 mL/g VS (54% increase) during SSAD of CS when F/S ratio was at 6. The improved CH4 production is consistent with increased relative abundance of several microbes that might play important roles in biomass degradation and CH4 generation. At higher F/S ratios (8 and 10), SSADs with different lime doses (0–5%) were all upset with accumulation of volatile fatty acids. Addition of 3.5% lime can obtain a net benefit of $18.4/tonne TS which are 44% of the gross benefit of power production ($41.5/tonne TS) via SSAD of CS and combined heat and power system.

The structure and electronic behaviour of anatase TiO2(001) surface loaded with noble metal atoms M (Ir, Pd and Pt) are systematically investigated by first-principles calculations. Meanwhile, the adsorption behaviour of CO on M-loaded anatase TiO2 is also studied. The results show that Ir and Pt atoms are more likely to be adsorbed on the O2 C (T1) site, while Pd atom is more easily adsorbed at the Ti5 C (T3) site. Among all of the considered systems, the formation energy of Pd/TiO2 (−2.500 eV) is the lowest one followed with Pt/TiO2 (−4.552 eV) and Ir/TiO2 (−6.298 eV). The adsorption mechanism of CO on the anatase TiO2(001) surface is studied by choosing the most stable configurations. The order of adsorption energy is CO/TiO2 (−1.065 eV) >CO/Pd/TiO2 (−2.535 eV) >CO/Pt/TiO2 (−3.326 eV) >CO/Ir/TiO2 (−3.593 eV). This theoretical study shows the adsorption mechanism of CO on the anatase TiO2(001 …

Lead-free silver niobate (AgNbO3, AN)-based dielectric ceramics have attracted intense attention for high-power energy storage applications since 2016 due to their electric-field-assisted antiferroelectric-ferroelectric phase transition. In this work, chemical compositions of 0.2 wt.% Mn-doped (1-x)AgNbO3-xCa(Hf0.2Ti0.8)O3 (AN-CHTx, x = 0.00–0.08) were designed and their ceramic samples were prepared in flowing oxygen via solid-state route. Our results show that the CHT modification not only enhance the antiferroelectricity stability but also the breakdown field (Eb). Further investigation reveals that the wider band gap (Eg) and suppression of oxygen vacancy play more important role in increasing Eb of AN-CHTx ceramics. Consequently, an ultrahigh recoverable energy density (Wrec) of 5.4 J/cm3 together with a relatively high energy conversion efficiency (η) of 66% is achieved under an electric field of 300 kV …

The influence of Mn, Fe, Si vacancies and Al-doped 4H–SiC on the electronic structures and magnetic properties are studied by first principles calculations. The results indicate both Mn and Fe monodoped can induce magnetism. Additionally, the phenomenon of ferromagnetism is observed in (Mn, Fe)-codoped 4H–SiC system, mainly contributed by Mn and Fe atoms. The ferromagnetic mechanism is that C atoms act as a medium between Mn atom and Fe atom, forming a Mn–C–Si–C–Fe coupling chain. The Si vacancies have a weaker effect on inducing ferromagnetism and Al atom doped has no obvious effect on the magnetic properties. Our study provides an effective method of tuning magnetism in 4H–SiC.

Diluted magnetic semiconductors with magneto-optical properties have very attractive properties in many applications (optical magnetic modulation). However, the major challenge limiting its further development is the ability to have excellent optical properties at room temperature. Through the first principle calculation of GGA + U method based on DFT calculation, we systematically calculated the electronic structure, magnetic properties and optical properties of Mn, Co and (Mn, Co) doped 3C–SiC. By (Mn, Co) co-doped 3C–SiC, we found that the system not only can obtain high total magnetic moment, but also has ferromagnetism, and the maximum Curie temperature reaches 886 K. The reason of ferromagnetism is because these ferromagnetic states are caused by p-d hybridization between adjacent C atoms and Mn and Co atoms. In addition, we found that the vacancy defect has an effect on the ferromagnetism …

Based on the first principles of the generalized gradient approximation method, the magnetic and optical properties of Fe-, Ni-doped and (Fe, Ni) co-doped LiNbO 3 crystals are studied. The results show that the mono-doped LiNbO 3 crystals contain magnetic atoms (Fe, Ni) leading to spin polarization, and (Fe, Ni) co-doped LiNbO 3 crystals tend to the ferromagnetic state with△ E F M of− 143 meV. The total magnetic moment of the (Fe, Ni) co-doped LiNbO 3 crystal is 5.97 μ B⁠, and the local magnetic moments of Fe and Ni are 2.99 μ B and 0.93 μ B⁠, respectively. It is interesting that the introduction of the Ga atom makes the ferromagnetic state (⁠△ E F M of− 285.4 meV) of the (Fe, Ni) co-doped LiNbO 3 system more stable than the anti-ferromagnetic state. Although Ga atoms do not contribute to the magnetic moment, the (Fe, Ni, Ga) co-doped LiNbO 3 is more conducive to the spin-polarized state. In addition, with …

The first principle plane wave pseudo-potential method based on density functional theory system is used to calculate and simulate the geometric structure, density of states and optical properties of intrinsic VC materials. And we further studied the adsorption performance of small gas molecules (CH 4, CO, H 2 O, H 2 S) on the surface of VC (001). The most stable adsorption geometry of CH 4, CO, H 2 O and H 2 S on the intrinsic VC (001) was determined, and the electronic structure and differential charge were calculated by the first principle method. The results show that the adsorption stability of the same molecule on the surface is related to the interaction position between the molecule and the surface after adsorption. According to the analysis of the differential charge density and the charge layout number, the charge layout number of the central atom C, O, S of the gas molecule increases after adsorption, and …

Two-dimensional (2D) van der Waals heterostructures (vdWHs), composed of two or more 2D monolayer (ML) materials, provide more opportunities for the application of 2D materials. Here, we have designed a 2D vertical MoSe2/MoSi2N4 vdWH and estimated its electronic and optical properties as well as the effects of applying strain and electric fields (E-fields) using first-principles calculations within density functional theory. We have indicated that the MoSe2/MoSi2N4 vdWH is a type-I direct bandgap vdWH with a bandgap of 1.39 eV, in which both the valence band maximum and conduction band minimum are mainly contributed by the MoSe2 ML. Intriguingly, the hole mobility in this vdWH is one order of magnitude higher than that in an isolated MoSe2 ML, up to 104 cm2 V−1 s−1, which is attributed to its larger in-plane stiffness and smaller deformation potential. Furthermore, the optical absorption is greatly …

This research aims to provide new insights into the performance and the microbial dynamics of the sludge fermentation process coupled with thermal hydrolysis. Two semi-continuous fermenters were operated under the mesophilic and thermophilic conditions at the retention time of three days. Thermal hydrolysis (TH) was applied either before (pre-hydrolysis) or after (post-hydrolysis) the fermentation process at a temperature, pressure, and stationary time of 170 °C, 115 psi, and 30 min, respectively. The process incorporating pre-hydrolysis achieved 10–16% higher solubilization and volatile fatty acids (VFAs) production than that of post-hydrolysis. Acetate and propionate prevailed in both process schemes. However, significantly higher iso-butyrate and lower butyrate were recovered through the fermentation of pre-hydrolyzed sludge. Pre-hydrolysis stimulated the growth of more kinetically efficient fermentative …

The magnetic and optical properties of pure, Fe, Co mono-doped and (Fe, Co) co-doped 3C-SiC were estimated, respectively, by using the plane wave pseudopotential method, with the first-principles of density functional theory. The calculation results show that pure 3C-SiC is non-magnetic semiconductor. The Fe, Co mono-doped and (Fe, Co) co-doped 3C-SiC exist spin-polarized and magnetic. The results of magnetization energy for (Fe, Co) co-doped 3C-SiC indicate the system exist FM coupling. From the imaginary part of the dielectric function and the absorption spectrum, it is found that the concentration of excited electrons in (Fe, Co) co-doped 3C-SiC crystals is less than that in pure 3C-SiC and Fe, Co mono-doped 3C-SiC, while the concentration of pure 3C-SiC is the largest. Both the mono-doped and co-doped systems have red-shifted absorption edges, and the optical band gap is reduced. The peak of …

By combining the GGA + U method, the magnetic and optical properties of (In, Mn) co-doped 4H–SiC and (In, 2Mn) co-doped 4H–SiC systems are calculated by first principles. The results show that the local magnetic moment of the (In, Mn) co-doped 4H–SiC system is 5.14 μB. And (In, 2Mn) co-doped 4H–SiC system can get the most stable ferromagnetic state, in which the energy difference △ EFM is 172.2 meV. The ferromagnetism of (In, 2Mn) co-doped 4H–SiC comes from the strong hybridization between the Si:2p orbitals, the C:2p orbitals and the Mn:3d orbitals near the dopant. In addition, the introduction of dopant atoms can reduce the band gap and improve conductivity. The doping system can weaken the maximum dielectric peak, thereby weakening the electromagnetic absorption ability of ϵ1(ω) in 4H–SiC. The doped system shows a red shift. And the doping system has lower transmittance in the infrared …

Finding the active sites of suitable metal oxides is a key prerequisite for detecting CH4. The purpose of the paper is to investigate the adsorption of CH4 on intrinsic and oxygen-vacancies CuO (111) and (110) surfaces using density functional theory calculations. The results show that CH4 has a strong adsorption energy of− 0.370 to 0.391 eV at all site on the CuO (110) surface. The adsorption capacity of CH4 on CuO (111) surface is weak, ranging from− 0.156 to− 0.325 eV. In the surface containing oxygen vacancies, the adsorption capacity of CuO surface to CH4 is significantly stronger than that of intrinsic CuO surface. The results indicate that CuO (110) has strong adsorption and charge transfer capacity for CH4, which may provide experimental guidance.

The adsorption of CO, H2S and CH4 on the intrinsic SnS2 monolayer and SnS2 monolayer with S-vacancy were studied by the first principle method. The most stable adsorption geometry was determined, and the electronic structure and differential charge were calculated. The results show that the band gap value of SnS2 monolayer with S-vacancy decreases and the surface activity increases. Compared with the intrinsic SnS2 monolayer, from the adsorption energy, electron transfer and adsorption distance of CO, H2S and CH4 on SnS2 monolayer with S-vacancy, it can be seen that the S vacancy system is more sensitive to these gases. The results show that the SnS2 monolayer with S-vacancy is more sensitive to three gases, which provides a new design idea for SnS2 based gas sensor.As seen from the graphical abstract, the gas molecules (CO, H2S, CH4) on SnS2 monolayer with S vacancy has stronger …

First-principles calculations based on density functional theory were employed to study the adsorption of gas molecules (CH 4, CO, H 2 O) on various SnO 2 (110) surfaces. We found that CO and CH 4 molecules are weakly adsorbed on intrinsic SnO 2 (110) surfaces, and intrinsic SnO 2 is sensitive only to the H 2 O molecule. Compared with the gas molecules adsorbed on the intrinsic SnO 2 surfaces, the significantly increased adsorption energy indicates that there is an improvement in the gas sensitivity properties of Co-doped SnO 2 (Co/SnO 2) and oxygen vacancy modified Co-doped SnO 2 (Co/V O/SnO 2) to CO, CH 4, and H 2 O gas. The CO adsorbed on the Co/V O/SnO 2 surface has the strongest adsorption energy (− 1.402 eV). We also studied the optical properties of the Co/SnO 2 and Co/V O/SnO 2 surfaces influenced by the three gas molecules. We found that the three gas molecules cause an …

Electrochemical nitrogen reduction reaction (NRR) is becoming increasingly promising alternatively to the traditional Haber-Bosch process but developing efficient electrocatalysts is still a challenge. In this job, we searched that the catalytic performance of Cr2B2 for NRR by way of density functional theory (DFT) calculations. We mainly screened out four favorable N2 adsorbed structures, including N2 adsorption on the B-B bonds, Cr-B bonds, top site of B and Cr atom. It was found that the largest adsorption energy was −1.235 eV when N2 was adsorbed on the Cr-B bond in a side-on structure, and has a better excellent NRR catalytic activity with the limiting potential is 0.29 V. The catalytic activity of all structures was better in the alternating mechanism of nitrogen reduction reaction. As the antibonding orbitals approach the Fermi level, the number of electrons in the antibonding orbitals increases. The limiting …

Anaerobic digestion has received significant attention in recent years due to dual benefits of waste diversion from landfill and bioenergy recovery. Among various temperature regimes, digesters operated under thermophilic (50–70 °C) condition has potential to provide several advantages over mesophilic (30–45 °C) and psychrophilic (<20 °C) conditions, which include faster degradation of organics and higher energy recovery. However, the operation of thermophilic digesters requires closer monitoring and control due to an additional risk of ammonia inhibition and irreversible acidification through the accumulation of volatile fatty acids. Conventional strategies to alleviate instabilities in thermophilic anaerobic digestion process have been focused primarily on the development of robust microbiome and co-digestion of complementary substrates. On the other hand, emerging strategies include the integration of …

First-principles calculations are performed to investigate the electronic structures and magnetic properties of (Mn, Ga) co-doped LiNbO3. The results show that it is available to tune the magnetism of Mn mono-doped LiNbO3, and the spin-polarized states and the magnetic moments mainly come from the unpaired 3d orbitals of Mn atoms. Furthermore, corresponding to the two Mn doped LiNbO3 system. Eight kinds of Mn atom positions are reviewed and the most stable configuration is verified. Several doping configurations indicate the presence of anti-ferromagnetic (AFM) coupling between two Mn dopants. And then we calculated (2Mn, Ga) co-doped LiNbO3 system. The exciting results show that the existence of ferromagnetic (FM) coupling between Mn and Ga dopants. The results demonstrate that the doped Mn atom will induce additional electron carrier into the LiNbO3. Ga itself does not contribute to …

The effect of (V, Fe) co-doped 4H-SiC on the magnetic and optical property has been investigated by using the density functional theory approach within the generalized gradient approximation plus Hubbard U term. Comparing with the pure 4H-SiC, we can find that V mono-doped 4H-SiC can induce a total magnetic moment of 2.03 μB, and Fe mono-doped 4H-SiC can induce a total magnetic moment of 3.97 μB. Further, we also find that the system of (V, Fe) co-doped 4H-SiC can induce a total magnetic moment with the value of 6.01 μB, and its ferromagnetic state is more stable than its antiferromagnetic state with a relative energy of −424.60 meV. Finally, we introduce a carbon vacancy to the system of (V, Fe) co-doped 4H-SiC, the results show that the ferromagnetic state will be enhanced. Due to the introduction of V and Fe atoms, red-shift phenomenon appears in the absorption spectrum, and the absorption …

The electronic structures and optical properties of two-dimensional carbonaceous graphene and graphdiyne were studied based on density functional theory (DFT). The results reveal that the graphene is more stable than the graphdiyne. In the vicinity of Fermi level, the electronic states of graphene and graphdiyne are mainly contributed by the C-2p state. The graphene exhibits better non-linear optical absorption properties and electrical conductivity under the visible light conditions. However, graphdiyne has excellent optical absorption and electrical conductivity in the range of partial infrared light. In addition to the transition from valence-band to conduction-band, there is also the inner-band transition near the Fermi level. The conclusion can provide theoretical basis for the application of two-dimensional carbon material graphene and graphdiyne in optoelectronic devices and photocatalysis.

The electronic structures, magnetic properties and optical properties of (Fe, Ni) co-doped 3C-SiC system are systematically studied based on the first principles calculation. The results show that Fe single doped, Ni single doped, and (Fe, Ni) co-doped system all induce magnetism. The most stable (Fe, Ni) co-doped systems is determined by calculating the magnetic coupling energies of ten different configuration. The (Fe, Ni) co-doped systems indicated that have a higher Curie temperature and the (1, 7) configuration significantly improves FM stability compared to other configurations. In addition, the results of the optical properties of (Fe, Ni) co-doped 3C-SiC exist absorption in the entire infrared, visible, and ultraviolet light regions, which has a substantial change compared with the undoped system. An effective way is comfirmed to improve the magnetic and optical performance of 3C-SiC.

Using the first-principles method, we studied the adsorption of CO molecules on SiC(111) surface with different layers. It is found that the adsorption of CO molecules on monolayer and bilayer SiC(111) surface is physical, while that on trilayer folded SiC(111) surface is chemical. The Si atom on the trilayer SiC(111) surface is the active adsorption site, and the O atom of the CO molecules prefers the Si atom on the SiC(111) surface. The calculated charge transfer and density of state (DOS) indicate that the electronic properties of the trilayer SiC(111) surface adsorbed CO molecules change. The trilayer SiC is promising for detecting CO molecules.

Using first-principles calculations, we have systematically investigated the structural, electronic structures and magnetic properties of Co-, Mn-doped and (Co, Mn) co-doped 4H–SiC. All calculations have been performed with the help of density functional theory, and the strong correlation effects are introduced by means of generalized gradient approximation+ U scheme. The energy difference between the ferromagnetic and anti-ferromagnetic has been evaluated. The results show that the substitution of Co–Co, Mn–Mn and Co–Mn couples in 4H–SiC have revealed ferromagnetic and half-metallic characteristics with the magnetic energy (△ E F M) of− 417.5,− 493.3 and− 537.0 meV, respectively. The calculations show that Co-, and Mn-doped 4H–SiC systems have the large magnetic moments of 5.94 and 6.04 μ B, respectively. The major contribution to the magnetic moment stems from the 3d orbitals of Co atoms …

C22H30N8O4S2Ni, monoclinic, P21/c (no. 14), a = 10.635(2) Å, b = 10.308(2) Å, c = 12.444(3) Å, β = 101.205(4)°, V = 1338.2(5) Å3, Z = 2, Rgt(F) = 0.0417, wRref(F2) = 0.0937, T = 296(2) K.

Constructing van der Waals heterostructures is deemed to be a novel scheme to circumvent the shortcomings of their components and bear potentials for applications in electronic devices. In this paper, we systematically investigate the structures, electronic properties, and band alignments of group VA/VA two-dimensional van der Waals heterostructures with the first-principles calculations. The investigated heterostructures possess typical type-II band alignment, in which the photoexcited electrons and holes can be effectively separated and their recombination can hence be suppressed, implying that the VA/VA two-dimensional heterostructures are good candidates for applications in optoelectronics. Meanwhile, an inherent electric field is observed at the interface of VA/VA two-dimensional van der Waals heterostructures. Interestingly, the band gaps of the heterostructures exhibits a strong strain-dependence …

The electronic structures and magnetic properties of diverse transition metal (TM= Fe, Co, and Ni) and nitrogen (N) co-doped monolayer MoS 2 are investigated by using density functional theory. The results show that the intrinsic MoS 2 does not have magnetism initially, but doped with TM (TM= Fe, Co, and Ni) the MoS 2 possesses an obvious magnetism distinctly. The magnetic moment mainly comes from unpaired Mo: 4d orbitals and the d orbitals of the dopants, as well as the S: 3p states. However, the doping system exhibits certain half-metallic properties, so we select N atoms in the V family as a dopant to adjust its half-metal characteristics. The results show that the (Fe, N) co-doped MoS 2 can be a satisfactory material for applications in spintronic devices. On this basis, the most stable geometry of the (2Fe–N) co-doped MoS 2 system is determined by considering the different configurations of the positions of …

In this paper, the adsorption of CO on the three anatase TiO2 (1 0 1) surface systems of intrinsic TiO2, an oxygen vacancy modification (VO/TiO2), and co-modified by an oxygen vacancy and a doped noble metal atom Os (Os/TiO2) are studied by first-principles. The results show that the adsorption performance of CO on intrinsic TiO2 is fine; especially the adsorption performance is greatly improved after adding defects. The adsorption energies of the TiO2 system, the VO/TiO2 system, and the Os/TiO2 system are −0.552 eV, −1.591 eV, and −3.971 eV, respectively. By analyzing the adsorption energy (ΔEads), bond length, charge distribution, density of states (DOS) and charge differential density (CDD) of the three systems, it is found that their adsorption mechanism and adsorption methods are different. The intrinsic TiO2 system is physical adsorption, and the carbon atom in CO has a strong interaction with Ti5C, but …

Based on density functional theory approach within the GGA+ U methods, the magnetic and optical properties of (Mn, Co) co-doped SnO 2 system are investigated. The results show that the local magnetic moments of Mn atom and Co atom in Mn monodoped SnO 2 and Co monodoped SnO 2 systems are 3.05 μ B and 0.76 μ B, respectively. For the (Mn, Co) co-doped SnO 2 system, the ferromagnetic state is more stable than the anti-ferromagnetic state with Δ E of− 133 meV. The ferromagnetism of (Mn, Co) co-doped SnO 2 comes from the strong hybridization between Mn: 3d, Co: 3d and O: 2p orbitals. Moreover, the band gap becomes narrower with transition metal (TM= Mn, Co atom) introduced to SnO 2 system. In the visible light range, the adsorption strength of transition metal (TM= Mn, Co atom) introduce to SnO 2 system is obviously enhanced. These results provide a new route for the potential applications of …

Anaerobic digestion (AD) is considered an attractive option for diversion of organic waste from landfills as well as the treatment of high-strength wastewater. Biomethane generated from AD can be used to meet on-site heat or electricity needs. However, the operation of AD facilities faces many challenges, including slow process kinetics, poor process stability due to inhibition by high ammonia level and organic acids accumulation, and low methane content in biogas. Therefore, further advancements in AD regarding process kinetics and robustness is a critical industry need. In recent years, considerable research interest focused on coupling microbial electrochemical systems with AD. The integration of microbial electrochemical systems, such as microbial electrolysis cells (MECs) with digesters, usually referred to as MEC-AD, can enhance process kinetics by stimulating electro-methanogenesis along with …

C30H28N8O2Br2Cd, triclinic, P1̄ (no. 2), a = 8.359(7) Å, b = 12.394(10) Å, c = 15.189(12) Å, α = 95.757(14)°, β = 90.593(16)°, γ = 106.961(15)°, V = 1496(2) Å3, Z = 2, Rgt(F) = 0.0467, wRref(F2) = 0.0998, T = 296(2) K.

C28H26N8O2Ni, orthorhombic, Aba2 (no. 41), a = 11.813(10) Å, b = 21.433(17) Å, c = 10.030(8) Å, V = 2539(4) Å3, Z = 4, Rgt(F) = 0.0457, wRref(F2) = 0.0992, T = 296(2) K.

The electronic structure and magnetic properties of 3d transition metal (Cr, Co)-codoped 4H–SiC were studied by density functional theory within GGA methods. The results show that all doped magnetic atoms have high magnetic properties in both Cr-doped and Co-doped 4H–SiC, resulting in the net magnetic moments of 3.03, 3.02 μB for Si35CrC36 and Si35CoC36. The electronic density of states reaches the peak at Fermi level, which is beneficial to the electronic transitions, indicating that Cr-doped 4H–SiC is a semi-metallic material. In addition, the magnetic properties of (Cr, Co)-codoped 4H–SiC were also calculated. The results show that the (Cr, Co)-codoped 4H–SiC system has more stable ferromagnetic properties with ΔEFM of −244.3 meV, and we estimated TC of about 470.8 K for the (Cr, Co)-codoped 4H–SiC system. The (Cr, Co)-codoped 4H–SiC can be ferromagnetic through some mechanism based on hybridization between local Cr:3d, Co:3d and C:2p states. These interesting discoveries will help promote the use of excellent SiC-based nanomaterials in spintronics and multi-function nanodevices in the near future.

Inspired by the recent use of two-dimensional nanomaterials as gas sensors, we used density functional theory calculations to study the adsorption of gas molecules (CH 4, CO and H 2 O) on sandwich vanadium dioxide tablets. The results showed that of all these gases, only the CH 4 gas molecule was the electron acceptor with significant charge transfer on the VO 2 sheet. The adsorption energies of CH 4, CO and H 2 O are− 229.5 meV,− 239.1 meV and− 388.3 meV, respectively. We have also compared the adsorption energy of three different gas molecules on the VO 2 surface, our calculation results show that when the three kinds of gases are adsorbed on the VO 2 surface, the order of the surface adsorption energy is H 2 O> CO> CH 4. It is also found that after adsorption of CH 4, CO and H 2 O molecules, the electronic properties of VO 2 sheet changed obviously. However, due to the strong adsorption of H 2 …

The electronic and magnetic properties of Co, Ni, (Co, Ni), (Co, Ni, Al) and (Co, Ni, VSi) doped 4H-SiC have been calculated using the first principles method based on density functional theory. The results show that the magnetic moments can be induced by the dopant Co or Ni atom. We also found that the (Co, Ni) co-doped 4H-SiC system is ferromagnetic at room temperature, with a △EFM value of −354.3 meV. Moreover, the 3d orbitals of Co, 3d orbitals of Ni and 2p orbitals of C can induce a spin-polarized state in (Co, Ni) co-doped 4H-SiC. Furthermore, for the (Co, Ni, Al) co-doped 4HSiC system, the ferromagnetic state is more stable than the anti-ferromagnetic state, with a △EFM value of −476.7 meV. The presence of Si vacancies (VSi) weakens the ferromagnetism state of (Co, Ni, VSi) doped 4H-SiC, with a △EFM value of −232.0 meV. The present results indicate that the (Co, Ni) co-doped 4H-SiC system is a …

In this work, 0.2 wt.% Mn-doped (1-x)AgNbO3-xBi0.5Na0.5TiO3 (x = 0.00–0.04) ceramics were synthesized via solid state reaction method in flowing oxygen. The evolution of microstructure, phase transition and energy storage properties were investigated to evaluate the potential as high energy storage capacitors. Relaxor ferroelectric Bi0.5Na0.5TiO3 was introduced to stabilize the antiferroelectric state through modulating the M1-M2 phase transition. Enhanced energy storage performance was achieved for the 3 mol% Bi0.5Na0.5TiO3 doped AgNbO3 ceramic with high recoverable energy density of 3.4 J/cm3 and energy efficiency of 62% under an applied field of 220 kV/cm. The improved energy storage performance can be attributed to the stabilized antiferroelectricity and decreased electrical hysteresis ΔE. In addition, the ceramics also displayed excellent thermal stability with low energy density variation …

Gas molecules (such as CH 4, CO, H 2 O, H 2 S, NH 3) adsorption on the pure and Au-doped WO 3 (001) surface have been studied by Density functional theory calculations with generalized gradient approximation. Based on the the calculation of adsorption energy, we found the most stable adsorption site for gas molecules by comparing the adsorption energies of different gas molecules on the WO 3 (001) surface. We have also compared the adsorption energy of five different gas molecules on the WO 3 (001) surface, our calculation results show that when the five kinds of gases are adsorbed on the pure WO 3 (001) surface, the order of the surface adsorption energy is CO> H 2 S> CH 4> H 2 O> NH 3. And the results show that NH 3 is the most easily adsorbed gas among the other four gases adsorbed on the surface of pure WO 3 (001) surface. We also calculated the five different gases on the Au-doped WO 3 …

Ceramics of 0.2 wt% Mn-doped (1-x)AgNbO3-xCaTiO3 (x = 0.00–0.04) were prepared in flowing oxygen with the solid state method. The microstructure, antiferroelectricity and energy storage performance were investigated to explore the potential for use in energy storage capacitors. Incorporation of CaTiO3 in AgNbO3 effectively inhibits the grain growth and gives rise to high dielectric breakdown strength. The temperature-dependent dielectric property and Raman spectroscopy measurements demonstrate the enhanced stability of antiferroelectricity by CaTiO3 addition through adjusting the M1–M2 phase transition. As a result of both improved antiferroelectricity and dielectric breakdown strength, a high recoverable energy density of 3.7 J/cm3 was achieved in the 2 mol% CaTiO3-modified AgNbO3 ceramic, which represents one of the highest recoverable energy density in recently studied lead-free ceramics …

Conductive materials have been incorporated in anaerobic bioreactors to stimulate direct interspecies electron transfer (DIET), a recently discovered microbial electron-sharing network. Previous studies emphasized the significance of electrocatalytic features associated with DIET, while research gaps are remaining in the understanding of how different operating temperatures and substrate variation will affect those electrochemical characteristics. Consequently, this study examined various electrochemical features, including biomass conductivity, pilA gene, heme-binding proteins, and electron transfers rates (kapp) for methanogenic biomass from conductive carbon fibers amended anaerobic bioreactors operated under different temperatures (20, 37, and 55 °C) with substrate variation (ethanol/propionate). Our results demonstrated a distinct temperature-dependent correlation between biomass conductivities, pilA …

Bilayer phosphorene homojunctions have attracted considerable interest owing to their natural bandgap and high carrier mobility. However, very little is known about the valuableness in arrays of bilayer phosphorene homojunctions with different rotated angles. In this work, we have presented angular modulated electronic and optical properties of rotated bilayer phosphorene employing first-principles calculations based on density functional theory. The angles in the homojunctions of the rotated bilayer phosphorene are set to be 26.02, 71.61, 110.54, 130.39⁠, and 149.01⁠, respectively, and the homojunctions demonstrate different bandgaps of 0.66 eV, 0.64 eV, 0.63 eV, 0.68 eV, and 0.67 eV, respectively, implying that these homojunctions are good candidates for application in optoelectronics and nanoelectronics. Interestingly, we found that the rotated bilayer phosphorene can greatly enhance the absorption of …

We studied the adsorption of CH4 molecules on different layers of SiC(111) surface by first principles. The results show that different layers of SiC(111) surface have an effect on the adsorption of CH4, and CH4 molecules are more selective for the trilayer SiC(111) surface. The calculated electron differential charge and the density of states indicate that the trilayer SiC(111) surface and CH4 molecules physically adsorbed. Besides, the trilayer SiC(111) surface has a larger adsorption energy than the monolayer and bilayer SiC(111) surface. Multi-layer SiC(111) surface is a promising candidate for detecting CH4 molecules.

Vertical integration of two-dimensional (2D) materials has recently emerged as an exciting method for the design of electronic and optoelectronic devices. Searching for ferromagnetic (FM) Van der Waals (vdW) heterostructures with high Curie temperature and multiple-band alignments is crucial to develop next-generation spintronic and optoelectronic nanodevices. In this work, first-principles calculations are employed to explore the structural and electronic properties of vertical tellurene/VS2 vdW heterostructure, and the FM vdW heterostructure is found in the tellurene/VS2 heterobilayer with Curie temperature of 150 K and type-III alignment. The ferromagnetic half-metal properties of two dimensional vertical tellurene/VS2 heterostructure provide the possibilities of realizing the high-temperature FM vdW heterostructures in practice.

The electronic structure and magnetic properties of (Fe, Ni) co-doped 4H-SiC-based dilute magnetic semiconductors were investigated by first-principles calculations. The (Fe, Ni) co-doped 4H-SiC exist spin-polarization due to the introduction of dopant atoms, resulting in splitting. The co-doped system is more prone to a ferromagnetic state, and the magnetization energy is larger than some known room temperature diluted magnetic semiconductors, indicating that the room temperature ferromagnetism (FM) is higher. The results show that the (Fe, Ni) co-doped 4H-SiC system is ferromagnetic at room temperature with△ E FM− 398.8 meV. The (Fe, Ni) co-doped 4H-SiC system exhibits strong magnetic properties due to strong coupling between Fe and Ni, resulting in strong spin polarization of nearby C atoms. We also studied the effect of silicon vacancies in the (Fe, Ni) co-doped 4H-SiC system. The results show that …

First-principles calculations are performed to investigate the electronic structures and magnetic properties of (Fe, Co)-codoped 4H-SiC using the generalized gradient approximation plus Hubbard U method. We find that 4H-SiC doped with an isolated Fe atom and an isolated Co atom produces a total magnetic moment of 5.98 μ B and 6.00 μ B respectively. We estimate T C of about 263.1 K for the (Fe, Co)-codoped 4H-SiC system. We study ferromagnetic and antiferromagnetic coupling in (Fe, Co)-codoped 4H-SiC. Ferromagnetic behavior is observed. The strong ferromagnetic couplings between local magnetic moments can be attributed to p–d hybridization between Fe, Co and neighboring C. However, the (Fe, Co, V Si)-codoped 4H-SiC system shows antiferromagnetic coupling when an Si vacancy is introduced in the same 4H-SiC supercell. The results may be helpful for further study on transition metal-codoped …

Two-dimensional lateral heterostructures (LHSs) carry unconventional physical properties due to their excellent adjustable band-offset and sensitive interface characteristics. In this paper, we have designed two kinds of seamless LHSs with excellent stabilities, the zigzag-zigzag (ZZ) InP/InAs LHS and the armchair-armchair (AA) InP/InAs LHS, and the changes in lattice structures and electronic properties under different strains are studied systematically by employing first-principles calculations based on density functional theory. Our results indicate that the ZZ and AA InP/InAs LHSs are indirect-bandgap semiconductors with a moderate bandgap. Surprisingly, it is found that the carrier mobility of holes for the ZZ InP/InAs LHS is as high as 6.954× 10 3 cm 2· V− 1· s− 1. The established ZZ and AA InP/InAs LHSs exhibit superior properties under uniaxial strains (a-direction and b-direction) and biaxial strain (ab-direction …

The adsorption properties of methane molecules (CH4) on the surface of noble metals doped anatase TiO2 (1 0 1) were studied using the first-principles method based on density functional theory (DFT). The noble metals M (M = Rh, Pd, Ag, Os, Ir, Pt and Au) are doped on the bridge oxygen vacancy defects of the anatase TiO2 surface, and the results show that the doping formation energy of Ir and Os are the lowest, −6.75 eV and −6.34 eV, respectively, indicating relatively stable systems. The adsorption energy analysis shows that both oxygen vacancy modification system and Os atom doping system can improve the stability of CH4 adsorption. By analyzing the density of state and charge density difference of the system, the orbital hybridization and charge transfer are verified the main reasons for the decrease of adsorption energy. The results show that Os atom doped TiO2 is a potential methane sensor material.

This study presents a microbiological diagnosis of a mesophilic high-solids anaerobic digestion (HSAD) system with percolate recirculation. The results demonstrated a significant decrease in microbial diversity in both the solid digestate and the liquid percolate. Also, the digestate from the top and middle sections of the digester had similar diversity, whereas the digestate from the bottom of the tank had a slightly lower diversity. These results suggest that despite percolate recirculation, substrate gradients might have developed across the system. Archaeal communities showed shifts towards known hydrogenotrophic and ammonia-tolerant methanogens (genera Methanocelleus, Methanolinea, Methanosarcina, vadin CA11, etc.), which was a consequence of decreased volatile fatty acids and increased ammonia-nitrogen levels over time. Compared to initial solid and liquid inoculum, the relative abundances of some …