Charge Density Difference Research Articles

The electronic and magnetic properties of Cr-doped ZnO monolayer at higher percentage by first principles calculations

The crystal structure, structural stability, electronic band structures and magnetization of Cr-doped ZnO monolayer (ML) have been investigated by GGA+U method using first principles calculations in this work. The stability of these systems is confirmed by the negative formation energies at different Cr concentrations. The calculated band gaps with and without the Hubbard U correction aligned well with other computational results. With the increase of Cr concentration, the band gap of Cr-doped ZnO monolayer decreases for the spin-up configuration. However, in the spin-down configuration, the band gap increases first and then decreases and the maximum band gap is obtained at 22.22% Cr concentrations. At 33.33% Cr concentration, the ZnO ML exhibits metallic behavior. The density of states (DOS) analysis reveals an asymmetric nature, indicating ferromagnetism in Cr-doped ZnO MLs at various concentrations, with a magnetic moment per Cr atom of approximately 3.99 μB. The total magnetic moment rises with increasing Cr concentration. Charge density difference analysis shows increased magnetization with higher Cr concentration. At 22.22% Cr concentration, the ZnO ML exhibits ferromagnetism and semiconducting properties, suggesting significant potential for spintronic applications as a diluted magnetic semiconductor.

Adsorption and Sensing Properties of Ni-Modified InSe Monolayer Towards Toxic Gases: A DFT Study

The emission of toxic gases from industrial production has intensified issues related to atmospheric pollution and human health. Consequently, the effective real-time monitoring and removal of these harmful gases have emerged as significant challenges. In this work, the density functional theory (DFT) method was utilized to examine the adsorption behaviors and electronic properties of the Ni-decorated InSe (Ni-InSe) monolayer when interacting with twelve gases (CO, NO, NO2, NH3, SO2, H2S, H2O, CO2, CH4, H2, O2, and N2). A comparative assessment of adsorption strength and sensing properties was performed through analyses of the electronic structure, work function, and recovery time. The results show that Ni doping enhances the electrical conductivity of the InSe monolayer and improves the adsorption capabilities for six toxic gases (CO, NO, NO2, NH3, SO2, and H2S). Furthermore, the adsorption of these gases on the Ni-InSe surface is characterized as chemisorption, as indicated by the analysis of the adsorption energy, density of states, and charge density difference. Additionally, the adsorption of CO, NO, NO2, and SO2 results in significant alterations to the bandgap of Ni-InSe, with changes of 18.65%, 11.37%, 10.62%, and −31.77%, respectively, underscoring its exceptional sensitivity. Moreover, the Ni-InSe monolayer exhibits a moderate recovery time of 3.24 s at 298 K for the SO2. Consequently, the Ni-InSe is regarded as a promising gas sensor for detecting SO2 at room temperature. This research establishes a foundation for the development of an Ni-InSe-based gas sensor for detecting and mitigating harmful gas emissions.

First-principles study on the failure and doping strengthening mechanisms at the interface of high-alumina ferritic heat-resistant steel/oxide film

This study employs first-principles calculations based on density functional theory to explore the failure mechanisms and enhancement strategies for the interface between high-aluminum ferritic heat-resistant steel and oxide film (α-Fe/Al₂O₃ interface). Establishing an interface model at the lowest-energy densely packed plane and performing tensile tests determined that fracture behavior manifests as ductile fracture at the interface. Further analysis of the charge density and differential charge density maps for various doped models confirmed the feasibility of strengthening the α-Fe/Al₂O₃ interface structure through alloy element doping. The results demonstrate that effective dopant elements (such as V, Mn, and Mo) can induce more electrons to transfer to the interface, increase electron concentration, and alter the chemical bonding nature of the interface, thereby significantly enhancing its bonding performance. This study proposes a method to enhance the interface of high-aluminum ferritic heat-resistant steel through doping, providing a theoretical foundation for further research on similar heat-resistant steel surfaces with Al₂O₃ films.

Dynamic Control of Asymmetric Charge Distribution for Electrocatalytic Urea Synthesis.

Constructing dual catalytic sites with charge density differences is an efficient way to promote urea electrosynthesis from parallel and CO2 reduction yet still challenging in static system. Herein, a dynamic system is constructed by precisely controlling the asymmetric charge density distribution in an Au-doped coplanar Cu7 clusters-based 3D frameworkcatalyst (Au@cpCu7CF). In Au@cpCu7CF, the redistributed charge between Au and Cu atoms changed periodically with the application of pulse potentials switching between -0.2 and -0.6 V and greatly facilitated the electrosynthesis of urea. Compared with the static condition of pristine cpCu7CF (FEurea = 5.10%), the FEurea of Au@cpCu7CF under pulsed potentials is up to 55.53%. Theoretical calculations demonstrated that the high potential of -0.6V improved the adsorption of *HNO2 and *NH2 on Au atoms and inhibited the reaction pathways of by-products. While at the low potential of -0.2V, the charge distribution between Au and Cu atomic sites facilitated the thermodynamic C-N coupling step. This work demonstrated the important role of asymmetric charge distribution under dynamic regulation for urea electrosynthesis, providing a new inspiration for precise control of electrocatalysis.

Enhanced VOCs adsorption on Group VIII transition metal-doped MoS2: A DFT study

Volatile organic compounds (VOCs) represent a significant category of toxic and harmful air pollutants. Among the various abatement techniques available for VOCs, adsorption technology is widely recognized as a cost-effective solution. In this study, density functional theory (DFT) was employed to calculate and compare the adsorption capacities of six typical VOCs on pristine MoS2 and MoS2 modified with Group VIII (MVIII) transition metals atoms. It is found that MVIII-MoS2 monolayer demonstratesa significant enhancement in adsorption capabilities for VOCsrelative to pristine MoS2. Among these Group VIII transition metals atoms, Fe, Ru and Os atoms exhibited the most significant VOCs adsorption enhancement, with Fe atoms demonstrating a particularly pronounced effect. This suggests a synergistic interaction between the metal dopants and the substrate. Density of states (DOS) and charge density difference analyses provided further insights into the mechanisms underlying improved adsorption capability. Interestingly, the introduction of MVIII atoms results in the emergence of a novel state density within the surface state of MoS2, thereby facilitating enhanced electron transfer between VOCs and the substrate. Charge density difference calculations further corroborated these findings, with certain configurations exhibiting significant electron cloud overlap. Such modification leads to more active electron transfer, thereby increasing the substrate’s affinity for VOC molecules and consequently improving the adsorption efficiency. The findings not only enhance the comprehension of VOC adsorption mechanisms on MoS2 but also underscore the potential of metal-doped two-dimensional materials for environmental applications.

Computational Insight into Transition Metal Atoms Anchored on B2C3P as Single‐Atom Electrocatalysts for Nitrogen Reduction Reaction

AbstractNH3 is not only an important chemical raw material but also a high‐energy storage chemical with zero carbon. Electrocatalytic nitrogen reduction reaction (NRR), which can be driven by clean electric energy under ambient conditions, has become a promising technology for NH3 synthesis due to its environmentally friendly properties. Because of the limitations of low yield and high overpotential, efficient catalysts are urgently needed to solve this problem. In this study, based on density functional theory method and high throughput screening strategy, the NRR was investigated on transition metal single atom anchored to 2D B2C3P surface (TM@B2C3P) as single‐atom catalysts (SACs). The results showed that V@B2C3P and Ti@B2C3P have good catalytic properties, and the limiting potentials were −0.10 and −0.24 V, respectively. Furthermore, the charge density difference and crystal orbital Hamilton population calculations demonstrated that the high catalytic activity can be attributed to the obvious charge transfer between TM@B2C3P and the adsorption intermediates. It is hoped that this work can play a certain role in exploring the application of SACs in NRR.

Construction of magnetically separable S-scheme BiFeO3/Cl-g-C3N4 heterostructure photocatalyst for simultaneous removal of Cr(Ⅵ) and tetracycline in aqueous solution: Performance and mechanism insight

A green, efficient and recyclable magnetic BiFeO3/Cl-g-C3N4 photocatalyst was prepared for the simultaneous removal of Cr(Ⅵ) and tetracycline (TC) from water by wet chemical and thermal synthesis methods. Experimental results revealed that BiFeO3/Cl-g-C3N4 achieved a removal efficiency of 96.1 % for Cr(Ⅵ) and 98.2 % for TC under visible light irradiation for 50 min at pH 6. The results of the work function, differential charge density, UV–vis DRS, PL, PC and EIS tests indicate the formation of S-scheme heterojunctions between BiFeO3 and Cl-g-C3N4, which exhibits superior carrier separation and migration efficiency. The evidence for interfacial charge transfer from BiFeO3 to Cl-g-C3N4 within BiFeO3/Cl-g-C3N4 was further corroborated by means of ISIXPS, EPR and KPFM. Moreover, calculations of the density of states demonstrate that the introduction of Cl enhances the reduction capability of BiFeO3/Cl-g-C3N4. Results from ESR tests and trapping experiments has demonstrated that the singlet oxygen (1O2) and electrons are the primary active species. Furthermore, the high removal rates of TC and Cr(VI) from industrial wastewater and groundwater, coupled with the lower ecotoxicity of TC degradation intermediates, indicate that BiFeO3/Cl-g-C3N4 has the potential for practical applications. After five cycles, the BiFeO3/Cl-g-C3N4 still removed 90.5 % of TC and 96 % of Cr(Ⅵ).

Comparison of gas-sensitive properties of Pb, Pd and Pt metal-doped Ti3C2X2 for aqueous zinc ion battery H2 gas

This work aims to provide early warning of uncontrolled reactions in aqueous zinc-ion batteries by timely and effectively detecting H2 gas. The large specific surface area and rich pore structure of Ti3C2X2 (X = F, O, and OH) make it a good gas-sensitive sensing material, and the gas-sensitive properties of the material can be improved by metal doping. Therefore, in this paper, the gas-sensitive response properties of Pb, Pd and Pt metal-doped Ti3C2X2 (M-Ti3C2X2) to H2 are compared based on density functional theory (DFT) calculations. The adsorption mechanism was analyzed by structure optimization, density of states, frontier molecular orbital theory and differential charge density, and the results were in high agreement. Doping of three metals, Pb, Pd and Pt, improved the adsorption capacity of Ti3C2X2 for H2 gas to different degrees. The simulation results show that the energy gap of Pb-Ti3C2(OH)2 adsorbed gas changes most obviously, and the maximum change value of energy gap (Eg) is 297.56 %. And Pt-Ti3C2F2 and Pt-Ti3C2O2 adsorbed H2 with large adsorption energies and large charge transfers indicating that they can be used as H2 removers. The energy gaps after the adsorption of H2 by M-Ti3C2O2 are 0.109 eV, 0.163 eV, and 0.082 eV, and the change of Eg is 24.77 %, 16.56 %, and 67.07 %, respectively. The change of Eg for the adsorption of H2 by Pt-Ti3C2O2 adsorbed H2 with a resistivity change of 67.07 %. This is caused by the irreversibility of adsorption due to too strong adsorption resulting in elongation of Pt-O bond length after adsorption. For the detection of H2, the properties of several doped materials were ranked as follows: Pb-Ti3C2(OH)2 > Pt-Ti3C2O2 > Pb-Ti3C2F2 > Pb-Ti3C2O2 > Pd-Ti3C2O2 > Pd-Ti3C2(OH)2 > Pt-Ti3C2F2 > Pt-Ti3C2(OH)2 > Pd-Ti3C2F2. In summary, it is shown that Ti3C2X2 doped with Pb, Pd and Pt metals is a potential H2 gas-sensitive material that can be a new material for online monitoring of fault gas content in aqueous zinc-metal energy storage batteries.

Vertical stacking approach for tailoring electronic and optical properties of ultrathin two-dimensional vdW heterostructures of P-MAB (M=Ti, Zr, Hf; A=S, B=Se)

The vertical staking in the form of hetersotructures, is an effective way to enhance the performance of corresponding isolated monolayers. Strong interactions between Janus monolayers (MAB) and Phosphorus (P) monolayers result in significant improvements in both physical and chemical properties compared to single layer configurations. Using first- principle (hybrid) calculations, we explore electronic structure and optical properties of P-MAB (M = Ti, Zr, Hf; A = S, B=Se) van der Waals heterostructures, for potential applications in electronic and optoelectronic devices. Ab initio molecular dynamic (AIMD) simulations confirm the thermal stability, while phonon spectra confirm the dynamical stabilities of these systems. Our analysis reveals that all configurations maintain semiconducting nature with an indirect bandgap. The type-II band alignment in the P-MAB heterostructures is demonstrated through calculations of the partial density of states (PDOS). Bader charge analysis and planar-averaged charge density differences indicate an electron transfer from the P monolayers to the MAB monolayer. Furthermore, our investigation of the dielectric function ϵ2(ω) shows that the lowest energy shift are primarily influenced by excitonic effects.

Theoretical Study of the Adsorption and Sensing Properties of Cr-Doped SnP3 Monolayer for Dissolved Characteristic Gases in Oil

Dissolved gas analysis (DGA) is a vital method for the online detection of transformer operation state. The adsorption performance of a SnP3 monolayer modified by transition metal Cr regarding six characteristic gases (CO, C2H4, C2H2, CH4, H2, C2H6) dissolved in oil was studied. The study reveals the relevant adsorption and gas-sensing response mechanisms through calculations of the adsorption energy, density of states, differential charge density, energy gap, and recovery time. The results display a considerable increase in the adsorption effect of the Cr-SnP3 monolayer on six gases. The CO, C2H2, and C2H4 gases lead to chemical adsorption, and the CH4, H2, and C2H6 gases lead to physical adsorption. Combined with the recovery time, the Cr-SnP3 monolayer has a strong adsorption effect on CO and C2H2 gases at normal temperatures and even high temperatures, and the adsorption is stable. C2H4 gas can be rapidly desorbed from the Cr-SnP3 monolayer at 398 K. Therefore, the Cr-SnP3 monolayer can be expected to serve as a CO and C2H2 gas adsorbent and a resistive gas sensor for C2H4 gas. This research offers a theoretical foundation for the development of the Cr-SnP3 monolayer in gas-sensitive materials.

Comparison of Gas-sensitive response of three metal-doped GaNNT with Pb, Pd and Pt after adsorption of hazardous gases

In this paper, we comparatively analyze the gas-sensing ability of Pb, Pd and Pt metal-doped GaNNT (M-GaNNT) materials for the hazardous H2S, SO2, NH3 and Cl2 gases. The adsorption structure, adsorption energy (Eads), density of states (DOS), differential charge density and frontier molecular orbital of the M-GaNNT adsorbed hazardous gas have been studied based on the density functional theory (DFT) calculations. The results show that the energy gap of Pb-GaNNT performs the largest change with an increasing percentage change of 358 % after the Cl2 adsorption compared with that before the Cl2 adsorption, while the energy gap of Pt-GaNNT has the least change with an average value of 20.8 %. The doping of metal atoms can effectively improve the gas-sensitivity of M-GaNNT, and the gas-sensitivity follows the order of Pb-GaNNT> Pd-GaNNT> Pt-GaNNT. The potential applications of M-GaNNT in gas sensor and adsorbent are then predicted through the analysis of the adsorption energy, sensitive response (SR) and recovery time (τ). Pb-GaNNT performs the best Cl2 gas removal since the largest Eads (-5.883 eV), largest SR (4.4 × 1015) and largest τ (2.9 × 1087s) can be determined for Cl2 adsorption on Pb-GaNNT. Furthermore, Pb-GaNNT is a good NH3 gas sensor since the related τ is only 2.9 s at 498 K, and a small Eads (-1.232 eV) with large SR (9.7 × 105) can be determined as well. The research findings in this paper provide a new sensor material option for both the detection and the removal of harmful gases, and the systematically theoretical method can spread to other systems.

Adsorption and gas sensing properties of CH4, C2H2, and C2H4 dissolved gases in transformer oil on Pdn(n = 1–4)-doped WTe2 monolayers: A DFT study

This paper investigates the potential of palladium (Pd) and its clusters-doped tungsten ditelluride (WTe2) monolayer materials for the detection of dissolved gases (such as CH4, C2H2, and C2H4) in transformer oil. Density functional theory (DFT) was used to study the effect of Pdn (n = 1–4) doping on the gas sensing and adsorption properties of WTe2 monolayer materials. The results show that Pdn doping can significantly improve the adsorption capacity and gas sensing performance of WTe2 to these gas molecules, especially showing excellent performance in detecting acetylene and ethylene. Studies have shown that Pdn doping improves the electrical conductivity of WTe2, making it more suitable for the development of gas sensors. Through the calculation of state density, molecular orbital and charge density difference, the adsorption mechanism of Pdn-doped WTe2 monolayer to different gas molecules was revealed. This study provides a theoretical basis and guidance for the development of efficient sensor materials for fault gas detection in transformer oil. In conclusion, the proposed Pd-doped WTe2 monolayer demonstrates promising potential for detecting dissolved gases in transformer oil. Future work will focus on experimental validation and further optimization of the material’s sensitivity and selectivity towards other gas species.

DFT insights on the adsorption and sensing performance of TMO-MoSSe for oil dissolved gases

The safe operation of oil-immersed transformers is crucial to the overall stability of the power system, making the prevention of partial discharges vitally important. This study proposes the use of MoSSe doped with TMOs (CuO, Ag2O, TiO2) to detect dissolved gases (CO, C2H2, CH4) in transformer oil. The adsorption of target gases on pristine and modified substrates is systematically studied using density functional theory (DFT). Given the unique sandwich structure of MoSSe, this paper explores the stability of the S-plane and Se-plane doping, ultimately selecting the S-plane for doping. Compared with the initial band gap of the substrate (1.598 eV), doping with CuO, Ag2O, and TiO2 reduces the band gap of MoSSe to 1.535, 0.677, and 0.752 eV, respectively. In terms of sensing performance, the improvement provided by the oxide particles on the substrate is confirmed by analyzing the geometric structure, density of states (DOS), differential charge density (DCD), and work function (WF) of the adsorption system. By comparing the adsorption parameters of the target gas adsorbed on both the doped and initial substrates, it is found that the metal oxides enhance the adsorption of the target gas on MoSSe. CH4 exhibits weak physical adsorption on the three modified substrates, with the order of adsorption capacity being: C2H2 > CO > CH4. The results of this study provide a theoretical basis for future applications in transformer condition monitoring and gas sensing.

Unraveling quantum capacitance of black phosphorene by the doping of non-metals for energy storage applications using DFT method

Supercapacitor plays a pivotal role as energy storage devices in the context of eliminating energy resources. Black Phosphorene (BP) is highly regarded as a potential electrode for supercapacitor (SC) because of its outstanding properties, including excellent carrier mobility and unique electronic properties. In this research work, the monolayer of BP and bilayer of BP (BP/BP) structure is investigated by using DFT. Moreover, the effect of doping and co-doping of non-metal (oxygen, nitrogen) in the mono- and bi-layer was also investigated to increase their performance by modulating the charge storage, and electronic properties of BP. The structural properties, density of states, quantum capacitance, surface charge density, bader charge analysis, isosurface charge density difference, integrated charge density of monolayer and bilayer are studied. The density functional theory (DFT) is used to calculate all above mention properties. DFT-D3 method with Becke-Johnson damping function is used as dispersion correction factor for all the calculations of bilayer. The calculated results find that bilayer structure gives better results as compared to monolayer structure. In this work, results also revealed that doping of oxygen and nitrogen atom significantly enhance the CQ and Q of mono- and bi-layer structure. For aqueous system, all the composites exhibited asymmetrical behavior except BP/BP bilayer. BP-N/BP-N (1369.8µC/cm2), and BP-O/BP-O (-1298.1µC/cm2) bilayer structure are best for anode and cathode material. In case of ionic/organic system, all composites showed asymmetrical behavior. BP-O/BP-O (-6053.5µC/cm2), and BP-N/BP-N (9329.8µC/cm2) bilayer structure is best cathode and anode material.

Advancing Zn-ion Battery Electrodes: Exploring the Potential of Graphene-Polythiophene Nanocomposites through First-Principles Analysis

AbstractThis research investigates the electronic and electrochemical properties of graphene-polythiophene (G/Pth) nanocomposites, as potential anode materials for Zn-ion batteries. By capitalizing on the distinctive attributes of these constituent materials, the research aims to unravel critical aspects, such as: interaction studies, electronic structure, charge transfer, charge density difference, the density of states (DOS), theoretical specific capacity, open circuit voltage, Zn-ion diffusion, and the structural stability of G/Pth. The findings present compelling insights into the adsorption process, revealing an exothermic adsorption energy of -2.79 eV and an adsorption height of 3.51 Å for the polythiophene onto the graphene nanosheets. The loading of Zn atoms onto the G/Pth nanocomposite, yields a noteworthy maximum specific capacity of 585 mAh/g. The nanocomposite exhibits an exceptionally low Zn diffusion barrier of 6 meV, thereby, facilitating a swift Zn diffusion across its surface. These results suggest the promising potential of G/Pth nanocomposites as anode materials for Zn-ion batteries, and hence, providing valuable insights into their electronic and structural properties. It is believed that this study, has significantly, contributed to the advancement of the comprehension of polymer substrate-based energy storage materials. Also, it establishes a foundation for further research to develop more effective and efficient solutions for energy storage in Zn-ion batteries. Graphical Abstract

Detection of harmful gases (NO, NO2) by GaN@MoSSe heterostructures embedded with transition metal (Cu, Fe and Mn) atoms: A DFT study

Monitoring and identifying air pollutants, such as NO and NO2, is crucial due to their detrimental impact on both the environment and human health. This work employs density functional theory (DFT) with the PBE + U functional to investigate the adsorption and sensing performance of NO and NO2 on transition metal (TM)-doped GaN@MoSSe heterostructures. The adsorption energy, charge transfer, electron localization functions, charge density difference, spin density, band gaps and density of states are analyzed. The findings reveal that a transition from physisorption to chemisorption occurs after TM atoms doping. Also, when the surface is embedded with Cu, Fe and Mn atoms, there is a significant improvement in the behavior related to gas adsorption. The bandgap and its variations lead to the change in surface electrical conductivity, thereby affecting the gas sensitivity of the adsorption system. Particularly, the CuGa-GaN@MoSSe and FeGa-GaN@MoSSe systems exhibit improved gas sensitivity toward NO due to their significant band gap reduction. Meanwhile, the CuSe−MoSSe@GaN, CuGa-GaN@MoSSe, FeGa-GaN@MoSSe and MnGa-GaN@MoSSe systems also demonstrate enhanced sensing capabilities for NO2. This work offers valuable theoretical insights for exploring the potential applications of TM-GaN@MoSSe heterostructures in gas sensing.

Investigation into geometric configurations and electronic properties of CeO2-supported gold clusters

A detailed understanding of the geometric structure and electronic properties of gold nanoparticles on the ceria surface is crucial for comprehending their unique catalytic activity. Using the first-principles method based on density functional theory, the adsorption of Aux (x = 1–4) clusters on the CeO2(111) surface was studied. It was discovered that the standing configurations of Au2 and Au3, as well as the tetrahedral structure of Au4, are the most stable adsorption structures. The stability of these configurations is jointly determined by the number and strength of Au-Au bonds, the Au-O bonding energy, and the interaction dynamics between the clusters and the substrate. The analysis of Bader charge, difference charge density and density of states suggested that lattice relaxation and electronic localization occur in the reduced Ce3+. The reduced amount and location of Ce3+ are significantly influenced by the position and charge transfer amount of Aux cluster. The adsorption of CO on Au4/CeO2(111) indicated that stronger Au-C bonding energy due to the hybridization of Au-5d and C-2p, thereby enhancing the catalytic activity for CO oxidation reactions.

Selectivity Modulation of Multistep Reduction Reactions by Gold Nanoclusters

The selective synthesis of valuable azo‐ and azoxyaromatic chemicals via transfer coupling of nitroaromatic compounds has been achieved by fine‐tuning the catalyst structure. Here, a direct method to modulate nitrobenzene reduction and selectively alter the product from azobenzene to azoxybenzene by employing the size effect of Au is reported. Au nanoclusters (NCs) with smaller sizes embedded in ZIF‐8 controllably converted nitrobenzene into azoxybenzene, while supported Au nanoparticles (NPs) catalyzed nitrobenzene reduction to azobenzene. X‐ray photoelectron spectroscopy (XPS) and Diffuse reflectance infrared Fourier transform spectroscopy on CO adsorption (CO‐DRIFTS) of Au NC/ZIF‐8 revealed a higher valence state and a lower electron density of Au than that of Au NP/ZIF‐8, combined with the desorption of azoxybenzene from the Au NC and Au NP surface, suggesting that the Au NCs with lower electron density exhibit stronger adsorption. Density functional theory (DFT) calculations and charge density difference maps indicated that azoxybenzene bonded to Au NC/ZIF‐8 with greater adsorption energy, resulting in more electron transfer between azoxybenzene and the generated Au sites, which inhibited further reduction of azoxybenzene and resulted in high azoxybenzene selectivity. The application of the size effect of Au particles to regulate nitrobenzene transfer coupling provided new insights into the structure‐selectivity relationships.

Selectivity Modulation of Multistep Reduction Reactions by Gold Nanoclusters.

The selective synthesis of valuable azo- and azoxyaromatic chemicals via transfer coupling of nitroaromatic compounds has been achieved by fine-tuning the catalyst structure. Here, a direct method to modulate nitrobenzene reduction and selectively alter the product from azobenzene to azoxybenzene by employing the size effect of Au is reported. Au nanoclusters (NCs) with smaller sizes embedded in ZIF-8 controllably converted nitrobenzene into azoxybenzene, while supported Au nanoparticles (NPs)catalyzed nitrobenzene reduction to azobenzene. X-ray photoelectron spectroscopy (XPS) and Diffuse reflectance infrared Fourier transform spectroscopy on CO adsorption (CO-DRIFTS) of Au NC/ZIF-8 revealed a higher valence state and a lower electron density of Au than that of Au NP/ZIF-8, combined with the desorption of azoxybenzene from the Au NC and Au NP surface, suggesting that the Au NCs with lower electron density exhibit stronger adsorption. Density functional theory (DFT) calculations and charge density difference maps indicated that azoxybenzene bonded to Au NC/ZIF-8 with greater adsorption energy, resulting in more electron transfer between azoxybenzene and the generated Au sites, which inhibited further reduction of azoxybenzene and resulted in high azoxybenzene selectivity. The application of the size effect of Au particles to regulate nitrobenzene transfer coupling provided new insights into the structure-selectivity relationships.

A first-principles investigation into the adsorption behavior and deposition mechanism of boron-containing gases on Si(100) surfaces during chemical vapor deposition

Polysilicon serves as a primary raw material in the production of solar cells and semiconductors. However, its impurity content, particularly boron, poses significant challenges during the chemical vapor deposition (CVD) process. Therefore, it is essential to investigate the behavior of boron impurities during CVD. In this study, we conducted first-principles calculations to explore the adsorption behavior and deposition mechanism of boron-containing gases (BCl3, BHCl2, B2H6) on the Si(100) surface. We considered different adsorption sites and performed a systematic analysis of various adsorption systems' adsorption energy, charge transfer, and electronic properties. Our findings indicate that BCl3, BHCl2, and B2H6 molecules undergo dissociative chemisorption at specific adsorption sites. Moreover, charge transfer analysis confirms that each of these adsorbed molecules functions as an electron acceptor. Subsequent analyses, including total charge density (TCD), charge density difference (CDD), total density of states (TDOS), and projected density of states (PDOS), collectively underscore the robust electronic interactions between the gaseous molecules and the Si(100) surface. Through the computation of transition states and energy barriers across three potential reaction pathways, we identify a predominant sequence: BCl3→BCl2+Cl→BCl+Cl→B+Cl, that governs boron impurity formation on the Si(100) surface during CVD. Our work elucidates the underlying microscopic mechanisms of boron-containing gas adsorption and deposition in the CVD context.