交互技术在手写公式编辑中的应用

遵循泛化计算理论 ,设计实现了一个联机手写公式编辑系统 ,以提高识别率和交互 (效 )率 该系统采用上下文感知技术来辅助切分、解决符号的二义性 ;采用备选择优、直接指定技术来修正字符的识别结果 ;采用局部放大解决笔画交叉时的分割问题 ;最后还给出一个补笔算法 实验表明 ,这些技术的应用使得数学公式的识别率和系统交互 (效 )率得到有效的提高 ,同时使该系统具有自然。

Classification of VxOy^q Clusters by △=2y＋q-5x

Vanadium oxide clusters VxOy^q（x≤8, q=0, ±1） are classified according to the oxidation index （△=2y＋q-5x） of each cluster. Density functional calculations indicate that clusters with the same oxidation index tend to have similar bonding characters, electronic structures, and reactivities. This general rule leads to the findings of new possible ground state struc- tures for V206 and V3O6＋ clusters. This successful application of the classification method on vanadium oxide clusters proves that this method is very effective in studying the bonding properties of early transition metal oxide clusters.

Photocatalytic performance of TiO_2 nanocrystals with/without oxygen defects

To investigate the role of oxygen defects on the photocatalytic activity of TiO2,the TiO2 nanocrystals with/without oxygen defects are successfully synthesized by the hydrothermal and sol‐gel methods,respectively.The as‐prepared TiO2 nanocrystals with defects are light blue and the absorption edge of light is towards the visible light region(~420 nm).Raman and X‐ray photoelectron spectroscopy(XPS)measurements all confirm that the concentration of oxygen vacancies in the TiO2 synthesized by the sol‐gel method is less than that synthesized through the hydrothermal route.The introduction of oxygen defects contributes to a new state in the band gap that narrows the band gap,which is the reason for the extension of light absorption into the visible light region.The photocurrent results confirm that this band‐gap narrowing enhances the photocurrent response under simulated solar light irradiation.The TiO2 with oxygen defects shows a higher photocatalytic activity for decomposition of a methylene blue solution compared with that of the perfect TiO2 sample.The photocatalytic mechanism is discussed based on the density functional theory calculations and photoluminescence spectroscopy measurements.

Effect of vacancy defects on electronic properties and activation of sphalerite(110) surface by first-principles

The electronic properties of sphalerite(110) surface with Zn-vacancy and S-vacancy were calculated by using density-functional theory,and the effects of vacancy defect on the copper activation of sphalerite were investigated.The calculated results indicate that surface state occurs in the band gap of Zn-vacancy sphalerite,which is from the contribution of S 3p orbital at the first layer of the surface.The presence of S-vacancy results in surface state appearing near the Fermi level and the bottom of conductor band,which are composed of S 3p and Zn 4s orbital,respectively.The surface structure of Zn-vacancy sphalerite is more stable than S-vacancy surface due to the occupation of Zn-vacancy by Cu atoms;hence,the substitution reaction of Cu for Zn vacancy is easier than the substitution of Cu for Zn atoms with S-vacancy surface.

Progress and prospects of photocatalytic conversion of low-concentration NOx

NOx can cause severe environmental problems such as acid rain and photochemical smog,endangering human health and the living environment.Among them,NO pollution accounts for about 95%.NO can exist stably in the air for a long time when the concentration is lower than the ppm level.Therefore,the conversion of low concentration of NO has attracted more and more attention.However,traditional physical or chemical methods are difficult to deal with low concentration of NO,having high requirements on equipment and being not cost‐effective.Semiconductor photocatalytic technology can convert low concentration of NO into non‐toxic products and reduce its harm.This work briefly surveys the commonly used materials,modification methods,and mechanisms for semiconductor photocatalytic conversion of low concentration of NO.In addition,the challenges and prospects of ppb level of NO treatment are also discussed,aiming to promote the development of semiconductor photocatalytic conversion of NO.

Expanded Porphyrin Nanosheet for Metal-Free Photocatalytic Water Splitting Using Visible Light

Photocatalytic water splitting to generate hydrogen gas is an ideal solution for environmental pollution and unsustainable energy issues.In the past few decades,many efforts have been made to increase the efficiency of hydrogen production.One of the most important ways is to achieve light absorption in the visible range to improve the conversion efficiency of solar energy into chemical energy,but it still presents great challenges.We here predicted a novel organic film,which can be obtained by polymerizing HTAP molecules,as an ideal material for photocatalytic water splitting.Based on firstprinciples calculations and Born-Oppenheimer quantum molecular dynamic simulations,the metal-free two-dimensional nanomaterial has been proven to be structurally stable,with a direct band gap of 2.12 e V,which satisfies the requirement of light absorption in the visible range.More importantly,the conduction bands and valence bands completely engulf the redox potentials of water,making the film be a promising photocatalyst for water splitting.This construction method through the topological periodicity of organic molecules provides a design scheme for the photocatalyst for water splitting.

Superior activity of Rh1/ZnO single-atom catalyst for CO oxidation

CO oxidation is of great importance in both fundamental study and industrial application.Supported noble metal catalysts are highly active for CO oxidation but suffer from the scarcity and high cost.Single-atom catalysts(SACs)can maximize the metal atom efficiency.Herein,ZnO nanowire(ZnO-nw)supported Rh,Au,and Pt SACs were successfully developed to investigate their CO oxidation performance.Interestingly,it was found that Rh1/ZnO-nw showed much higher activity than the other noble metals which are usually regarded as good candidates for CO oxidation.In addition,the Rh SAC possessed high stability in high-temperature CO oxidation under simulated conditions in the presence of water and hydrocarbons.The high activity and stability make Rh1/ZnO-nw promising for practical applications,especially in the automotive exhaust emission control.Theoretical calculations indicate that the CO oxidation proceeds via the Mars-van Krevelen mechanism and the lowest barrier for the rate-limiting O2 dissociation at a surface oxygen vacancy site is a key factor in determining the observed highest activity of Rh1/ZnO-nw amongst the studied SACs.

Activity and selectivity of propane oxidative dehydrogenation over VO_3/CeO_2(111) catalysts: A density functional theory study

The oxidative dehydrogenation（ODH） of propane on monomeric VO3 supported by CeO2（111）（VO3/CeO 2（111）） is studied by periodic density functional theory calculations. Detailed energetic, structural, and electronic properties of these reactions are determined. The calculated activation energies of the breaking of the first and second C–H bonds of propane on the VO3/CeO2（111） catalyst are compared, and it is found that both the unique structural and electronic effects of the VO3/CeO2（111） catalyst contribute to the relatively easy rupture of the first C–H bond of the propane molecule during the ODH reaction. In particular, the so-called new empty localized states that are mainly constituted of O2 porbitals of the ceria-supported VO3 species are determined to be crucial for assisting the cleavage of the first C–H bond of the propane molecule. Following this they become occupied and the remaining C–H bonds become increasingly difficult to break owing to the increasing repulsion between the localized 4 felectrons at the Cecations, resulting in the adsorption of more H and other moieties. This work illustrates that CeO2-supported monomeric vanadium oxides can exhibit unique activity and selectivity for the catalytic ODH of alkanes to alkenes.

Microscopic mechanism of perfluorocarbon gas formation in aluminum electrolysis process

In view of the unclear cause of perfluorocarbons(PFCs)emission in the anode effect stage of aluminum electrolysis,the microscopic formation mechanism of PFCs was studied by density functional theory calculation and X-ray photoelectron spectroscopy(XPS).It is found that the discharge of fluorine containing anions([F]−)on carbon anode first causes the substitution of C—H by C—F and further results in the saturation of aromatic C—C bonds,leading to the appearance of—CF_(3)or—C_(2)F_(5)group through six-carbon-ring opening.Elimination of—CF_(3)and—C_(2)F_(5) with F atom could be a likely mechanism of CF_(4) and C_(2)F_(6) formation.XPS results confirm that different types of—CF_(x) group can be formed on anode surface during electrolysis,and the possibility that[F]−discharges continuously at the C edge and finally forms different C—F bonds in quantum mechanical calculation was verified.

Physical Properties of Ⅲ-Antiminodes—a First Principles Study

A comprehensive first principles study of III-Antimonide binary compounds is hardly found in literature. We report a broad study of structural and electronic properties of boron antimonide （BSb）, aluminium antimonide （AlSb）, gallium antimonide （GaSb） and indium antimonide （InSb） in zineblende phase based on density functional theory （DFT）. Our calculations are based on Full-PotentiM Lineaxized Augmented Plane wave plus local orbitals （FP- L（APWq-lo）） method. Different forms of exchange-correlation energy functional and corresponding potential are employed for structural and electronic properties. Our computed results for lattice parameters, bulk moduli, their pressure derivatives, and cohesive energy are consistent with the available experimental data. Boron antimonide is found to be the hardest compound of this group. For band structure calculations, in addition to LDA and GGA, we used GGA-EV, an approximation employed by Engel and Vosko. The band gap results with GGA-EV are of significant improvement over the earlier work.

Metal organic framework‐ionic liquid hybrid catalysts for the selective electrochemical reduction of CO_(2) to CH4

The electrochemical reduction of CO_(2) towards hydrocarbons is a promising technology that can utilize CO_(2) and prevent its atmospheric accumulation while simultaneously storing renewable en‐ergy.However,current CO_(2) electrolyzers remain impractical on a large scale due to the low current densities and faradaic efficiencies(FE)on various electrocatalysts.In this study,hybrid HKUST‐1 metal‐organic framework‒fluorinated imidazolium‐based room temperature ionic liquid(RTIL)electrocatalysts are designed to selectively reduce CO_(2) to CH_(4).An impressive FE of 65.5%towards CH_(4) at-1.13 V is achieved for the HKUST‐1/[BMIM][PF_(6)]hybrid,with a stable FE greater than 50%maintained for at least 9 h in an H‐cell.The observed improvements are attributed to the increased local CO_(2) concentration and the improved CO_(2)‐to‐CH_(4) thermodynamics in the presence of the RTIL molecules adsorbed on the HKUST‐1‐derived Cu clusters.These findings offer a novel approach of immobilizing RTIL co‐catalysts within porous frameworks for CO_(2) electroreduction applications.

Quantum Chemical Study of Potential Energy Surface in the Formation of Atmospheric Sulfuric Acid

A new potential energy surface （PES） for the atmospheric formation of sulfuric acid from OH＋SO2 is investigated using density functional theory and high-level ab initio molecular orbital theory. A pathway focused on the new PES assumes the reaction to take place between the radical complex SO3.HO2 and H2O. The unusual stability of SO3.HO2 is the principal basis of the new pathway, which has the same final outcome as the current reaction mechanism in the literature but it avoids the production and complete release of SO3. The entire reaction pathway is composed of three consecutive elementary steps： （1） HOSO2＋O2-＋SO3.HO2, （2） SO3.HO2＋H20-＋SO3·H2O·HO2, （3） SO3.H20.HO2-＋H2SO4＋HO2. All three steps have small energy barriers, under 10 kcal/rnol, and are exotherrnic, and the new pathway is there- fore favorable both kinetically and therrnodynarnically. As a key step of the reactions, step （3）, HO2 serves as a bridge molecule for low-barrier hydrogen transfer in the hydrolysis of SO3. Two significant atmospheric implications are expected frorn the present study. First, SO3 is not released from the oxidation of SO2 by OH radical in the atmosphere. Second, the conversion of SO2 into sulfuric acid is weakly dependent on the humidity of air.

First-principles study on electronic structure and optical properties of N-doped P-type β-Ga_2O_3

The band structure, density of states, electron density difference and optical properties of intrinsic β-Ga2O3 and N-doped β-Ga2O3 were calculated using first-principles based on density functional theory. After N doping, the band gap decreases, shallow acceptor impurity levels are introduced over the top of the valence band and the absorption band edge is slightly red-shifted compared to that of the intrinsic one. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. All calculation results indicate that N-doping is a very promising method to get P-type β-Ga2O3.

Influence of Cl substitution on the electronic structure and catalytic activity of ceria

Cl-containing cerium dioxide(Ce O2) catalysts have been found to exhibit unique catalytic activities. In the present work, using density functional theory calculations with the inclusion of on-site Coulomb correction, we systematically studied the effect of Cl on the physicochemical properties of Ce O2 surfaces by substituting one subsurface O with Cl. The calculated results show that substituting an O atom with a Cl atom results in structural distortion and the reduction of one surface Ce4+ cation to Ce3+. The protruding Ce3+ cation greatly improves the adsorption energy of O2 to produce an active O2- species, and maintains the catalytic oxidation cycle of CO on Ce O2(110). These results may help us obtain a better understanding of Cl-ceria interacting systems and provide some guidance for the design of effective Ce O2-based catalysts.

A multiphase nickel iron sulfide hybrid electrode for highly active oxygen evolution

Development of highly active electrocatalysts for oxygen evolution reaction(OER)is one of the critical issues for water splitting,and most reported catalysts operate at overpotentials above 190 mV.Here we present a multiphase nickel iron sulfide(MPS)hybrid electrode with a hierarchical structure of iron doped NiS and Ni3S2,possessing a benchmark OER activity in alkaline media with a potential as low as 1.33 V(vs.reversible hydrogen electrode)to drive an OER current density of 10 mA cm^-2.The Fe doped NiS,combined with highly conductive disulfide phase on porous Ni foam,is believed to be responsible for the ultrahigh activity.Furthermore,density functional theory simulation reveals that partially oxidized sulfur sites in Fe doped NiS could dramatically lower the energy barrier for the rate-determining elementary reaction,thus contributing to the active oxygen evolution.

Bimetallic phthalocyanine heterostructure used for highly selective electrocatalytic CO_(2) reduction

Heterogeneous molecular catalysts,such as metal phthalocyanines,are efficient electrocatalysts for CO_(2) reduction reaction(CO_(2)RR).However,the rational design and synthesis of a molecular catalyst-based heterostructure for CO_(2)RR remains challenging.Herein,we developed a crystalline bimetallic phthalocyanine heterostructure electrocatalyst(CoPc/FePc HS),which achieved an excellent CO_(2)-to-CO conversion efficiency(99%)and outstanding long-term stability after 10 h of electrocatalysis.Density functional theory calculations revealed that the enhancement of CO_(2)RR performance could be attributed to the distinct electron transfer pattern between FePc and CoPc.The heterostructural engineering in molecular catalysts would inspire a unique approach for improving CO_(2)RR performance.

Stoichiometry design in hierarchical CoNiFe phosphide for highly efficient water oxidation

Rational composition design of trimetallic phosphide catalysts is of significant importance for enhanced surface reaction and efficient catalytic performance.Herein,hierarchical Co_(x)Ni_(y)Fe_(z)P with precise control of stoichiometric metallic elements(x:y:z=(1-10):(1-10):1)has been synthesized,and Co_(1.3)Ni_(0.5)Fe_(0.2)P,as the most optimal composition,exhibits remarkable catalytic activity(η=320 mV at 10 mA cm^(−2))and long-term stability(ignorable decrease after 10 h continuous test at the current density of 10 mA cm^(−2))toward oxygen evolution reaction(OER).It is found that the surface P in Co_(1.3)Ni_(0.5)Fe_(0.2)P was replaced by O under the OER process.The density function theory calculations before and after long-term stability tests suggest the clear increasing of the density of states near the Fermi level of Co_(1.3)Ni_(0.5)Fe_(0.2)P/Co_(1.3)Ni_(0.5)Fe_(0.2)O,which could enhance the OH−adsorption of our electrocatalysts and the corresponding OER performance.

Temperature-controlled synthesis of heterostructured Ru-Ru_(2)P nanoparticles embedded in carbon nanofibers for highly efficient hydrogen production

Developing highly efficient,cost-effective,and stable electrocatalysts for hydrogen evolution reaction(HER)is of considerable importance but remains challenging.Herein,we report the fabrication of a robust Ru-based electrocatalyst,which comprises heterostructured Ru-Ru_(2)P nanoparticles that are embedded in the N,P-codoped carbon nanofibers(CNFs),through a synthetic strategy involving electrospinning and temperature-controlled pyrolysis treatment.The as-prepared Ru-Ru_(2)P catalyst(Ru-Ru_(2)P@CNFs)shows excellent HER catalytic activities with low overpotentials of 11 and 14 mV in acidic and alkaline media,respectively,to achieve a current density of 10 mA cm^(−2),which are superior to the individual components of pure Ru and Ru_(2)P catalysts.Density functional theory calculations demonstrate the existence of electronic coupling effect between Ru and Ru_(2)P at the heterointerfaces,leading to a well-modulated electronic structure with optimized hydrogen adsorption strength and enhanced electrical conductivity for efficient HER electrocatalysis.In addition,the overall synthetic strategy can be generalized for the synthesis of a series of transitional metal phosphide-based nanofibers,thereby holding a remarkable capacity for various potential applications.

Room-temperature liquid metal synthesis of nanoporous copper-indium heterostructures for efficient carbon dioxide reduction to syngas

Nanoporous metals show promising performances in electrochemical catalysis.In this paper,we report a self-supporting bimetallic porous heterogeneous indium/copper structure synthesized with a eutectic gallium-indium(EGaIn)material on a copper substrate.This nanoporous copper-indium heterostructure catalyst exhibits excellent performance in the reduction of carbon dioxide to syngas.The ratio of H_(2)/CO is tunable from 0.47 to 2.0 by changing working potentials.The catalyst is highly stable,showing 96%maintenance of the current density after a 70-h continuous test.Density functional theory calculations reveal that the indium/copper interface induces charge redistribution within the copper surface,leading to the formation of two distinct active sites,namely,Cu^(δ)and Cu0,and enabling a high-performance generation of CO and H_(2).This work provides a new strategy for obtaining self-supporting nanoporous metal electrode catalysts.