广义化的电荷分解分析(GCDA)方法

电荷分解分析(CDA)是一种重要的深入研究电荷转移问题的方法。本文对CDA进行了介绍,阐述了计算中需要注意的问题,并提出了一种新的CDA形式,称为广义化的电荷分解分析(GCDA)。在HF、DFT级别GCDA与CDA等价,但GCDA能更好地用于后HF计算,而且还明确考虑了开壳层时的计算形式。通过以OC-BH3和顺式二氯二胺合铂体系作为测试实例,我们发现各种理论级别下GCDA的结果都较为合理且定性相符,但在定量上有所区别,特别是d项存在大体趋势:低HF成份的泛函 >高HF成份的泛函 >HF ≥MP2 >CCSD。文中还对GCDA计算时基组的选择进行了讨论。

隐式溶剂下丙氨酸体系电荷分解分析的理论计算

采用密度泛函理论中的B3LYP方法优化隐式溶剂下丙氨酸(Ala)分子的几何构型,并用同法计算隐式水(H_2O)及甲醇溶剂下Ala体系片段的轨道波函数及电荷分解分析(CDA).结果表明,在隐式溶剂甲醇和H2O下,CH_3片段的扩展电荷分解分析(ECDA)计算结果相差0.001 3;NH_2片段的ECDA计算结果相差0.000 8,定量结果基本一致,CH_3和NH_2片段的CDA计算结果ri对二者的定性结果基本一致.

密度泛函理论方法研究Mn^2+催化丙氨酸反应的机理及催化活性

采用密度泛函理论的BP86-D3方法研究了Mn^2+催化丙氨酸转化反应的机理及催化活性.得到15个稳定构型和12个过渡态,最稳定构型的结合自由能为-710.8kJ·mol^-1.Mn^2+可以催化丙氨酸发生质子迁移反应、手性转化反应、裂解失CO反应和裂解失H2O反应;对应的吉布斯自由能垒分别为7.7kJ·mol^-1、78.7kJ·mol^-1、166.4kJ·mol^-1和225.2kJ·mol^-1.丙氨酸质子迁移反应和手性转化反应通道的决速步基元反应相同,自由能垒是119.1kJ·mol^-1,相应反应较易发生.丙氨酸裂解反应通道的最高自由能垒为225.2kJ·mol^-1,反应较难发生.

CuO＋氧化苯直接形成苯酚反应机理的理论研究

在UB3LYP/6-31G(d,p)水平下研究了CuO+氧化苯形成苯酚反应的详细机理,同时计算了单态和三态势能面.计算结果表明,苯与CuO+间相互作用主要为σ键,反馈π键较弱.CuO+氧化苯形成苯酚反应通过非自由基氢摘取机理完成,主要包括C—H键活化和苯基与羟基耦合两步反应.C—H键活化为整个反应的决速步骤.C—H键活化步骤涉及势能面交叉,且自旋交叉与动力学相关.CuO+氧化苯形成苯酚反应在气相中很容易进行.

杂双核(H)Rh-Cr配合物中乙烯插入Rh^I-H键反应的密度泛函研究

采用密度泛函理论B3LYP方法研究了配体和配位数对乙烯插入杂双核(CO)4Cr(μ-PH2)2RhH(Ln)(L=CO或PH3,n=1或2)配合物中Rh—H键反应的影响.计算结果表明,六配位乙烯复合物中乙烯与铑之间轨道相互作用主要为乙烯到铑中心的σ供体相互作用;而五配位乙烯复合物中乙烯与铑中心间相互作用涉及乙烯到铑中心的σ供体相互作用和铑到乙烯的π反馈作用.PH3配体在热力学上不利于该反应.处于氢配体对位的膦配体能加速乙烯插入反应.乙烯插入的五配位反应途径占优势.Cr(CO)4部分的引入降低了乙烯插入反应的活化能.

苯丙氨酸体系片段CDA及轨道相互作用

采用密度泛函理论中的B3LYP方法,在3-21G基组水平上优化气相S型苯丙氨酸(S-Phe)手性对映体的几何构型,计算Phe分子轨道波函数及片段轨道间的电荷分解分析(CDA),并给出片段COOH,C_6H_5和NH_2形成过程中片段间的轨道相互作用图.结果表明:片段COOH,C_6H_5和NH_2基于CDA的ri项最大正值分别为r_(19),r_(17)和r_(15),即分子轨道的形成导致占据片段轨道的电子向交叠区域转移;片段COOH和NH_2基于CDA的r_i项最大负值分别为r_(44)和r_(35),即分子轨道的形成导致片段间占据片段轨道的电子从交叠区域移走.

The roles and mechanism of cocatalysts in photocatalytic water splitting to produce hydrogen

Photocatalytic hydrogen(H2)evolution via water spilling over semiconductors has been considered to be one of the most promising strategies for sustainable energy supply in the future to provide non-pollution and renewable energy.The key to efficient conversion of solar-chemical energy is the design of an efficient structure for high charge separation and transportation.Therefore,cocatalysts are necessary in boosting photocatalytic H2 evolution.To date,semiconductor photocatalysts have been modified by various cocatalysts due to the extended light harvest,enhanced charge carrier separation efficiency and improved stability.This review focuses on recent developments of cocatalysts in photocatalytic H2 evolution,the roles and mechanism of the cocatalysts are discussed in detail.The cocatalysts can be divided into the following categories:metal/alloy cocatalysts,metal phosphides cocatalysts,metal oxide/hydroxide cocatalysts,carbon-based cocatalysts,dual cocatalysts,Z-scheme cocatalysts and MOFs cocatalysts.The future research and forecast for photocatalytic hydrogen generation are also suggested.

Latest progress in hydrogen production from solar water splitting via photocatalysis,photoelectrochemical,and photovoltaic-photoelectrochemical solutions

Hydrogen production via solar water splitting is regarded as one of the most promising ways to utilize solar energy and has attracted more and more attention. Great progress has been made on photocatalytic water splitting for hydrogen production in the past few years. This review summarizesthe very recent progress (mainly in the last 2–3 years) on three major types of solar hydrogenproduction systems: particulate photocatalysis (PC) systems, photoelectrochemical (PEC) systems,and photovoltaic‐photoelectrochemical (PV‐PEC) hybrid systems. The solar‐to‐hydrogen (STH)conversion efficiency of PC systems has recently exceeded 1.0% using a SrTiO3:La,Rh/Au/BiVO4:Mophotocatalyst, 2.5% for PEC water splitting on a tantalum nitride photoanode, and reached 22.4%for PV‐PEC water splitting using a multi‐junction GaInP/GaAs/Ge cell and Ni electrode hybrid system.The advantages and disadvantages of these systems for hydrogen production via solar watersplitting, especially for their potential demonstration and application in the future, are briefly describedand discussed. Finally, the challenges and opportunities for solar water splitting solutions are also forecasted.

Photovoltaic Performance of Triphenylamine Dyes-sensitized Solar Cells Employing Cobalt Redox Shuttle and Influence of π-conjugated Spacers

Developing photosensitizers suitable for the cobalt electrolyte and understanding the structure-property relationship of organic dyes is warranted for the dye-sensitized solar cells （DSSCs）. The DSSCs incorporating tris（1,10-phenanthroline）eobalt（Ⅱ/Ⅲ）-based redox elec- trolyte and four synthesized organic dyes as photosensitizers are described. The photovoltaic performance of these dyes-sensitized solar cells employing the cobalt redox shuttle and the influences of the w-conjugated spacers of organic dyes upon the photovoltage and photocur- rent of mesoscopic titania solar cells are investigated. It is found that organic dyes with thiophene derivates as linkers are suitable for DSSCs employing cobalt electrolytes. DSSCs sensitized with the as-synthesized dyes in combination with the cobalt redox shuttle yield an overall power conversion efficiency of 6.1% under 100 mW/cm2 AM1.5 G illumination.

Study on Water-Soluble Organic Reducing Substances: II. Organic Reducing Substances Produced from Anaerobic Decomposition of Milk Vetch (Astragalus sinicus L.)

The characteristics of electric charge and molecular weight distribution,oxidation-reduction regimes,e.g.Eh and amounts of organic reducing substances produced by milk vetch during anaerobic decomposition process,were studied by using electrochemical methods.Interaction between soils and organic reducing substances was also observed.The results indicate that the organic reducing substances were mainly the organic compounds with negative and amphoteric charges,which were distributed in two groups at anodic peak potentials of 0.25 and 0.69 volt in differential pulse voltammograms,respectively.Their apparent molecular weights are all less than 700 daltons,in which those active in oxidation-reducion reaction were distributed in the fraction with apparent molecular weight less than 200 daltons.The organic reduction substances can be oxidized by manganese oxides in their interaction with soils.

Enhanced photoelectrochemical water splitting using a cobalt-sulfide-decorated BiVO_(4) photoanode

Solar-driven water splitting is considered as a promising method to mitigate the energy crisis and various environmental issues.Bismuth vanadate(BiVO_(4))is photoanode material with tremendous potential for photoelectrochemical(PEC)water splitting.However,its PEC performance is severely hindered owing to poor surface charge transfer,surface recombination at the photoanode/electrolyte junction,and sluggish oxygen evolution reaction(OER)kinetics.In this regard,a novel solution was developed in this study to address these issues by decorating the surface of BiVO_(4)with cobalt sulfide,whose attractive features such as low cost,high conductivity,and rapid charge-transfer ability assisted in improving the PEC activity of the BiVO_(4)photoanode.The fabricated photoanode exhibited a significantly enhanced photocurrent density of 3.2 m A cm^(-2)under illumination at 1.23 V vs.a reversible hydrogen electrode,which is more than 2.5 times greater than that of pristine BiVO_(4).Moreover,the Co S/BiVO_(4)photoanode also exhibited considerable improvements in the charge injection yield(75.8%vs.36.7%for the bare BiVO_(4)film)and charge separation efficiency(79.8%vs.66.8%for the pristine BiVO_(4)film).These dramatic enhancements were primarily ascribed to rapid charge-transport kinetics and efficient reduction of the anodic overpotential for oxygen evolution enabled by the surface modification of BiVO_(4)by Co S.This study provides valuable suggestions for designing efficient photocatalysts via surface modification to improve the PEC performance.

Enhancing an internal electric field by a solid solution strategy for steering bulk-charge flow and boosting photocatalytic activity of Bi_(24)O_(31)Cl_(x)Br_(10-x)

Constructing bismuth oxyhalide solid solutions with a single homogeneous phase have intrigued the research community;however,a deeper understanding of the intrinsic origin for improved bulk-charge separation is still unclear.Herein,a series of Bi_(24)O_(31)Cl_(x)Br_(10-x) solid solutions with the same structural characteristics were synthesized by crystal structure regulation.Combining density functional theory calculation,Kelvin probe force microscopy,and zeta potential testing results,an enhanced internal electric field(IEF)intensity between[Bi_(24)O_(31)]and[X]layers was achieved by changing halogen types and ratios.This greatly facilitated bulk-charge separation and transfer efficiency,which is significant for the degradation of phenolic organic pollutants.Owing to the enhanced IEF intensity,the charge carrier density of Bi_(24)O_(31)Cl_(4)Br_(6) was 33.1 and 4.7 times stronger than that of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Therefore,Bi24O31Cl4Br6 had an optimal photoactivity for the degradation of bisphenol A,which was 6.21 and 2.71 times higher than those of Bi_(24)O_(31)Cl_(10) and Bi_(24)O_(31)Br_(10),respectively.Thus,this study revealed the intrinsic mechanism of the solid solution strategy for photocatalytic performance enhancement with respect to an IEF.

Time-resolved infrared spectroscopic investigation of Ga_(2)O_(3) photocatalysts loaded with Cr_(2)O_(3)-Rh cocatalysts for photocatalytic water splitting

Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.

扩展卟啉Ni(Ⅱ),Pd(Ⅱ)和Pt(Ⅱ)单金属配合物光电性质的理论研究

采用密度泛函方法（DFT），对六元扩展卟啉的Ni（Ⅱ），Pd（Ⅱ）和Pt（Ⅱ）单金属配合物进行了几何构型的优化．在优化的基础上，对6种配合物进行了电荷分解分析（CDA）、扩展电荷分解分析（ECDA）以及前线分子轨道的成分分析．基于几何优化的结果，在含时密度泛函（TD-DFT）方法下，计算了6种配合物的吸收光谱．得出如下结论：无论是R型还是M型配合物，Pd（Ⅱ）同六元扩展卟啉的电荷转移值都是最大的，从而也说明中心金属Pd（1Ⅱ）同配体之间的相互作用也是最大的．通过对吸收光谱和前线分子轨道的分析，在B带最大吸收峰上，R型配合物主要显示出由金属到配体的电荷转移（MLCT），并且金属轨道在跃迁成分中占比越大，最大吸收峰红移越远，其最大吸收峰顺序λ（Ni@RHP）（492nm）〉λ（Pr@RHP）（477nm）〉λ（Pd@RHP，（467nm）．而对于M型配合物的Ni@MHP和Pd@MHP，90％以上的跃迁来自配体内的电荷转移（ILCT），并且展示了几乎相等的最大吸收峰（540nm）．Pt@MHP与前者相比有40nm的红移，并展示了MLCT的吸收特征。

Photoelectrode for water splitting: Materials,fabrication and characterization

Photoelectorchemical（PEC） water splitting is an attractive approach for producing sustainable and environment-friendly hydrogen. An efficient PEC process is rooted in appropriate semiconductor materials, which should possess small bandgap to ensure wide light harvest, facile charge separation to allow the generated photocharges migrating to the reactive sites and highly catalytic capability to fully utilize the separated photocharges. Proper electrode fabrication method is of equal importance for promoting charge transfer and accelerating surface reactions in the electrodes. Moreover,powerful characterization method can shed light on the complex PEC process and provide deep understanding of the rate-determining step for us to improve the PEC systems further. Targeting on high solar conversion efficiency, here we provide a review on the development of PEC water splitting in the aspect of materials exploring, fabrication method and characterization. It is expected to provide some fundamental insight of PEC and inspire the design of more effective PEC systems.

Controlling metallic Co^(0) in ZIF-67-derived N-C/Co composite catalysts for efficient photocatalytic CO_(2) reduction

An efficient photocatalytic CO_(2) reduction has been reported in ZIF-67-derived-Co nanoparticles(NPs)encapsulated in nitrogen-doped carbon layers(N-C/Co).This work demonstrates that the pyrolysis temperature is crucial in tuning the grain size and components of metallic Co^(0) of N-C/Co composite catalysts,which optimizes their photocatalytic activities.Syntheses were conducted at 600,700,and 800℃ giving the N-C/Co-600,N-C/Co-700,and N-C/Co-800 samples,respectively.N-C layers can well wrap the Co NPs obtained at a low pyrolysis temperature(600℃)owing to their smaller grains than those of other samples.A high metallic Co^(0) content in the N-C/Co-600 sample can be attributed to the effective inhibition of surface oxidation.By contrast,the surface CoOx oxides in the N-C/Co-700 and N-C/Co-800 samples cover inside Co cores,inhibiting charge separation and transfer.As a result,the N-C/Co-600 sample yields the best photocatalytic activity.The carbon monoxide and hydrogen generation rates are as high as 1.62×10^(4) and 2.01×10^(4)μmol g^(−1)h^(−1),respectively.Additionally,the Co NPs make composite catalysts magnetic,enabling rapid and facile recovery of catalysts with the assistance of an external magnetic field.This work is expected to provide an instructive guideline for designing metal-organic framework-derived carbon/metal composite catalysts.

Boosting visible-light-driven water splitting over LaTaON_(2) via Al doping

LaTaON_(2)is an attractive visible-light-active photocatalyst for water splitting due to its broad visible light absorption as far as 650 nm and proper band edge positions.Notwithstanding these promising properties,LaTaON_(2)generally exhibits poor photocatalytic activity because of its high defect concentration that severely hinders charge separation.Here,LaTaON_(2)has been modified by doping Al into the Ta sublattice,i.e.,LaTa_(1−x)Al_(x)O_(1+y)N_(2−y)(0≤x≤0.20).Al doping not only inhibits the defect concentration and increases surface hydrophilicity but also maintains the desired visible light absorption of LaTaON_(2).These important modifications substantially ameliorate the charge separation conditions within LaTaON_(2)and are responsible for a much enhanced photocatalytic performance for water redox reactions under visible light illumination.Under optimal conditions,the Al-doped LaTaON_(2)delivers an apparent quantum efficiency of 1.17%at 420±20 nm for water oxidation into O_(2),outperforming most LaTaON_(2)-based photocatalysts.These findings highlight Al as a useful dopant to open up the photocatalytic potential of metal oxynitrides whose activity is often undermined by a high defect concentration.

Construction of AFLT States by Reflection Method and Recursion Formula

The AFLT states|PY1,Y2has reflection symmetry,Sn|PY1,Y2=|PY2,Y2,nb=2P,where S is the screening charge.AFLT state can be constructed using this reflect symmetry.We propose a recursion formula for this construction.The recursion formula is factorized completely.

Unique Cd1-xZnxS@WO3-x and Cd1-xZnxS@WO3-x/CoOx/NiOx Z-scheme photocatalysts for efficient visible-light-induced H2 evolution

Artificial Z-scheme photocatalytic systems have received considerable attention in recent years because they can achieve wide light-absorption, high charge-separation efficiency, and strong redox ability simultaneously. Nevertheless, it is still challenging to exploit low-cost and stable Zscheme photocatalysts with highly-efficient H2 evolution from solar water-splitting so far. Herein, we report a novel all-solidstate Z-scheme photocatalyst Cd1-xZnxS@WO3-x consisting of Cd1-xZnxS nanorods coated with oxygen-deficient WO3-x amorphous layers. The Cd1-xZnxS@WO3-x exhibits an outstanding H2 evolution reaction(HER) activity as compared with Pt-loaded Cd1-xZnxS and most WO3- and Cd S-based photocatalysts, due to the generation of stronger reducing electrons through the appropriate Zn-doping in Cd1-xZnxS and the enhanced charge transfer by introducing oxygen vacancies(W^5+/OVs) into the ultrathin WO3-x amorphous coatings. The optimal HER rate of Cd1-xZnxS@WO3- xis determined to be 21.68 mmol h^-1 g^-1, which is further raised up to 28.25 mmol h^-1 g^-1(about 12 times more than that of Pt/Cd1-xZnxS) when Cd1-xZnxS@WO3-x is hybridized by Co Ox and Ni Oxdual cocatalysts(Cd1-xZnxS@WO3-x/CoOx/NiOx)through in-situ photo-deposition. Moreover, the corresponding apparent quantum yield(AQY) at 420 nm is significantly increased from 34.6% for Cd1-xZnxS@WO3-x to 60.8% for Cd1-xZnxS@WO3-x/CoOx/NiOx. In addition, both Cd1-xZnxS@WO3-x and Cd1-xZnxS@WO3-x/CoOx/NiOx demonstrate good stability towards HER. The results displayed in this work will inspire the rational design and synthesis of high-performance nanostructures for photocatalytic applications.

Unconventional materials:the mismatch between electronic charge centers and atomic positions

The complete band representations(BRs)have been constructed in the work of topological quantum chemistry.Each BR is expressed by either a localized orbital at a Wyckoff site in real space,or by a set of irreducible representations in momentum space.In this work,we define unconventional materials with a common feature of the mismatch between average electronic centers and atomic positions.They can be effectively diagnosed as whose occupied bands can be expressed as a sum of elementary BRs(eBRs),but not a sum of atomic-orbital-induced BRs(aBRs).The existence of an essential BR at an empty site is described by nonzero real-space invariants(RSIs).The"valence"states can be derived by the aBR decomposition,and unconventional materials are supposed to have an uncompensated total"valence"state.The high-throughput screening for unconventional materials has been performed through the first-principles calculations.We have discovered 423 unconventional compounds,including thermoelectronic materials,higher-order topological insulators,electrides,hydrogen storage materials,hydrogen evolution reaction electrocatalysts,electrodes,and superconductors.The diversity of these interesting properties and applications would be widely studied in the future.