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921.
Delocalized \begin{document}$\pi_3^6$\end{document} Bond in OX\begin{document}$_2$\end{document} (X=Halogen) Molecules
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Yi-han Tang Pu Yang Meng-yuan Chen Yu-ru Wang Jia-xin Wang Jia-wei Xu 《化学物理学报(中文版)》2022,35(3):542-550
OX\begin{document}$_2$\end{document} (X=halogen) molecules was studied theoretically. Calculation results show that delocalized \begin{document}$\pi_3^6$\end{document} bonds exist in their electronic structures and O atoms adopt the sp\begin{document}$^2$\end{document} type of hybridization, which violates the prediction of the valence shell electron pair repulsion theory of sp\begin{document}$^3$\end{document} type. Delocalization stabilization energy is proposed to measure the contribution of delocalized \begin{document}$\pi_3^6$\end{document} bond to energy decrease and proves to bring extra-stability to the molecule. These phenomena can be summarized as a kind of coordinating effect. 相似文献
922.
Kinetics and Mechanism of Catalytic Reduction of U(VI) with Hydrazine on Platinum Catalysts in Nitric Acid Media
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Xiao-teng Zhang Shuai Hao Fei-fei Tang Bin Li Xian-ming Zhou Li-sheng Liu Liang-shu Xia 《化学物理学报(中文版)》2022,35(5):813-822
The kinetics of U(IV) produced by hydrazine reduction of U(VI) with platinum as a catalyst in nitric acid media was studied to reveal the reaction mechanism and optimize the reaction process. Electron spin resonance (ESR) was used to determine the influence of nitric acid oxidation. The effects of nitric acid, hydrazine, U(VI) concentration, catalyst dosage and temperature on the reaction rate were also studied. In addition, the simulation of the reaction process was performed using density functional theory. The results show that the influence of oxidation on the main reaction is limited when the concentration of nitric acid is below 0.5 mol/L. The reaction kinetics equation below the concentration of 0.5 mol/L is found as: -dc(UO22+)/dt)=kc0.5323(UO22+)c0.2074(N2H5+)c-0.2009(H+). When the temperature is 50 ℃, and the solid/liquid ratio r is 0.0667 g/mL, the reaction kinetics constant is k=0.00199 (mol/L)0.4712/min. Between 20 ℃ and 80 ℃, the reaction rate gradually increases with the increase of temperature, and changes from chemically controlled to diffusion-controlled. The simulations of density functional theory give further insight into the influence of various factors on the reaction process, with which the reaction mechanisms are determined according to the reaction kinetics and the simulation results. 相似文献
923.
A Mechanistic Switch in C-H Bond Activation by Elusive Fe\begin{document}$^\text{V}$\end{document} (O)(TAML) Reaction Intermediate: A Theoretical Study
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The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta's experiment was mechanistically studied herein by means of density functional theory calculations. Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates (the aliphatic cyclohexane, 2, 3-dimethylbutane and the aromatic toluene, ethylbenzene and cumene). For the aliphatic substrates, C-H oxidation by the oxidant Fe\begin{document}$^{\rm{V}}$\end{document} (O)(TAML) is a hydrogen atom transfer process; whereas for the aromatic substrates, C-H oxidation is a proton-coupled electron transfer (PCET) process with a proton transfer character on the transition state, that is, a proton-coupled electron transfer process holding a proton transfer-like transition state (PCET(PT)). This difference is caused by the strong \begin{document}$\pi$\end{document} -\begin{document}$\pi$\end{document} interactions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates, which has a "pull" effect to make the electron transfer from substrates to the Fe=O moiety inefficient. 相似文献
924.
925.
Catechol adsorbed on TiO2 is one of the simplest models to explore the relevant properties of dye-sensitized solar cells. However, the effects of water and defects on the electronic levels and the excitonic properties of the catechol/TiO2 interface have been rarely explored. Here, we investigate four catechol/TiO2 interfaces aiming to study the influence of coverage, water, and defects on the electronic levels and the excitonic properties of the catechol/TiO2 interface through the first-principles many-body Green's function theory. We find that the adsorption of catechol on the rutile (110) surface increases the energies of both the TiO2 valence band maximum and conduction band minimum by approximately 0.7 eV. The increasing coverage and the presence of water can reduce the optical absorption of charge-transfer excitons with maximum oscillator strength. Regarding the reduced hydroxylated TiO2 substrate, the conduction band minimum decreases greatly, resulting in a sub-bandgap of 2.51 eV. The exciton distributions in the four investigated interfaces can spread across several unit cells, especially for the hydroxylated TiO2 substrate. Although the hydroxylated TiO2 substrate leads to a lower open-circuit voltage, it may increase the separation between photogenerated electrons and holes and may therefore be beneficial for improving the photovoltaic efficiency by controlling its concentration. Our results may provide guidance for the design of highly efficient solar cells in future. 相似文献
926.
Dr. Jia Wang Xuhui Liu Dr. Chunxu Wang Wanyi Zhang Prof. Zhengkun Qin 《ChemistryOpen》2022,11(2):e202100208
The spin polarization of carbon nanomaterials is crucial to design spintronic devices. In this paper, the first-principles is used to study the electronic properties of two defect asymmetric structures, Cap-(9, 0)-Def [6, 6] and Cap-(9, 0)-Def [5, 6]. We found that the ground state of Cap-(9, 0)-Def [6, 6] is sextet and the ground state of Cap-(9, 0)-Def [5, 6] is quartet, and the former has a lower energy. In addition, compared with Cap-(9, 0) CNTs, the C adatom on C30 causes spin polarization phenomenon and Cap-(9, 0)-Def [6, 6] has more spin electrons than Cap-(9, 0)-Def [5, 6] structure. Moreover, different adsorb defects reveal different electron accumulation. This finding shows that spin polarization of the asymmetric structure can be adjusted by introducing adatom defects. 相似文献
927.
The first principle computational screening was performed to investigate the effect of selected dopants for Li3PS4 sulfide solid electrolyte on its ionic conductivity and stability toward moisture. The results suggest that substitution P5+ using isovalent cations whose electronegativity (EN) value is closer to the value of S has more significant effects on the ionic conductivity, whereby W5+ and Sb5+ can improve most. Similarly, aliovalent cation substitutions with compensating changes in the lithium-ion concentration, particularly those with a lower oxidation state and higher EN, such as Cu2+, effectively enhance the lithium-ion conductivity in this structure. For cation dopants, it is found that ionic conductivity improvement of Li3PS4 is the synergetic effect of EN and oxidation number of the dopant as well as the material's lattice parameter change. Oxides of the considered cation dopants can also improve the ionic conductivity of the material but have much lower lithium-ion conductivity than the cases of cation dopants. However, the metal oxide dopants, particularly those derived from soft Lewis' acid cations, show a marginal improvement in moisture stability of the Li3PS4 electrolyte. The effect of halides and metal halide dopants on the lithium-ion conductivity and moisture stability of Li3PS4 electrolyte are also studied. It is found that metal halides are more effective than any other dopants in improving the ionic conductivity of Li3PS4. 相似文献
928.
Huijun Wang Jie Gao Dr. Xiang Xu Dr. Baogen Liu Lingyun Yu Yadong Ren Dr. Rui Shi Prof. Zheng Zeng Prof. Liqing Li 《化学:亚洲杂志》2021,16(9):1118-1129
To investigate the effects of oxygen-containing functional groups on the adsorption of volatile organic compounds (VOCs) with different polarity, oxygen-rich porous carbon materials (OPCs) were synthesized by heat treatment of glucose/potassium oxalate material. The carbon material had a large specific surface area (1697 m2 g−1) and a high oxygen content (18.95 at.%). OPC exhibited high adsorption capacity of toluene (309 mg g−1) and methanol (447 mg g−1). The specific surface area and total pore volume determined the adsorption capacity of toluene and methanol at the high-pressure range, while the oxygen-containing groups became the main factor affecting the methanol adsorption at the low-pressure range due to the hydrogen bond interaction through the density functional theory (DFT) calculations. This study provides an important hint for developing a novel O-doped adsorbent for the VOCs adsorption applications and analyzing the role of oxygen-containing groups in the VOCs adsorption under the low-pressure range. 相似文献
929.
Sambath Baskaran Prof. Cong-Qiao Xu Ya-Fei Jiang Yang-Gang Wang Prof. Dr. Jun Li 《Chemphyschem》2021,22(4):378-385
Single-atom catalysts (SACs) have attracted extensive attention owing to their high catalytic activity. The development of efficient SACs is crucial for applications in heterogeneous catalysis. In this article, the geometric configuration, electronic structure, stabilitiy and catalytic performance of phosphorene (Pn) supported single metal atoms (M=Ru, Rh, Pd, Ir, Pt, and Au) have been systematically investigated using density functional theory calculations and ab initio molecular dynamics simulations. The single atoms are found to occupy the hollow site of phosphorene. Among the catalysts studied, Ru-decorated phosphorene is determined to be a potential catalyst by evaluating adsorption energies of gaseous molecules. Various mechanisms including the Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and trimolecular Eley-Rideal (TER) mechanisms are considered to validate the most favourable reaction pathway. Our results reveal that Ru−Pn exhibits outstanding catalytic activity toward CO oxidation reaction via TER mechanism with the corresponding rate-determining energy barrier of 0.44 eV, making it a very promising SAC for CO oxidation under mild conditions. Overall, this work may provide a new avenue for the design and fabrication of two-dimensional materials supported SACs for low-temperature CO oxidation. 相似文献
930.
Molybdenum disulfide (MoS2) has been regarded as one of the most promising candidates for replacing Pt group noble metals as an efficient electrocatalyst to enhance the hydrogen evolution reaction (HER) in consideration of its relatively high earth abundance. Recent studies show that the catalytic efficiency of MoS2 for HER can be promoted by the presence of 1T-phase MoS2. It is hard to precisely control the formation of 1T-MoS2, however, due to its metastability relative to 2H-MoS2. Elevating the stability of 1T phase allotrope is therefore of great importance and could be realized by replacing divalent S with monovalent elements or groups according to crystal field theory, which has been demonstrated through our first-principles density functional theory (DFT) calculation results. Differential Gibbs free energy analysis for hydrogen adsorption (ΔGH*) suggest that 1T and 1T′ MoSO (O doped MoS2) might be taken as potential candidate catalysts for HER process with better performance than 1T and 1T′ MoS2. We also propose a probable approach to synthesize 1T and 1T′ MoSO under oxidation circumstance environment of graphene oxide. 相似文献