Atomic Ni directional-substitution on ZnIn_(2)S_(4) nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic activity.Herein,the atomic Ni was introduced into the lattice of hexagonal ZnIn_(2)S_(4) nanosheets(Ni/ZnIn_(2)S_(4))via directionalsubstituting Zn atom with the facile hydrothermal method.The electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction reaction.Besides the optimized light absorption range,the elevation of Efand ECBendows Ni/ZnIn_(2)S_(4) photocatalyst with the increased electron concentration and the enhanced reduction ability for surface reaction.Moreover,ultrafast transient absorption spectroscopy,as well as a series of electrochemical tests,demonstrates that Ni/ZnIn_(2)S_(4) possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn_(2)S_(4).These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity,in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn_(2)S_(4).Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges,but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.

Solar energy conversion on g-C3N4 photocatalyst:Light harvesting,charge separation,and surface kinetics

Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.

Kinetics and Dynamics of Photocatalyzed Dissociation of Ethanol on Ti02（110）

The kinetics and dynamics of photocatalyzed dissociation of ethanol on TiO2（110） sur- face have been studied using the time-dependent and time-resolved femtosecond two-photon photoemission spectroscopy respectively, in order to unravel the photochemical properties of ethanol on this prototypical metal oxide surface. By monitoring the time evolution of the photoinduced excited state which is associated with the photocatalyzed dissociation of ethanol on Ti5c sites of Ti02（ll0）, the fractal-like kinetics of this surface photocatalytic reaction has been obtgined. The measured photocatalytic dissociation rate on reduced TiO2（l10） is faster than that on the oxidized surface. This is attributed to the larger defect density on the reduced surface which lowers the reaction barrier of the photocatalytic reaction at least methodologically. Possible reasons associated with the defect electrons for the acceleration have been discussed. By performing the interferometric two-pulse corre- lation on ethanol/TiO2（l10） interface, the ultrafast electron dynamics of the excited state has been measured. The analyzed lifetime （24 fs） of the excited state is similar to that on methanol/TiO2（110）. The appearance of the excited state provides a channel to mediate the electron transfer between the TiO2 substrate and its environment. Therefore studying its ultrafast electron dynamics may lead to the understanding of the microscopic mechanism of photocatalysis and photoelectrochemical energy conversion on TiO2.

One-step hydrothermal synthesis of S-defect-controlled ZnIn_(2)S_(4) microflowers with improved kinetics process of charge-carriers for photocatalytic H_(2) evolution

Engineering lattice defects in two-dimensional(2 D) sulfide semiconductors has been accepted as an effective strategy to enhance the efficiency of the solar-to-fuels conversion.Although many researches have proven the lattice defect-mediated photocatalytic activity of ZnIn_(2)S_(4),the artificial control of Sdefects for optimizing the charge-carrier kinetics process in ZnIn_(2)S_(4) has long been a challenging task.Herein,we report a facile one-step method to modulate the lattice S-content of ZnIn_(2)S_(4) microflowers(MFs) only through adjusting the used amount of S-precursor in the hydrothermal solution that contains the metal precursors with a fixed Zn/In stoichiometric ratio at 1:2.We also demonstrated that the Svacancies at the In facets were the main type of lattice defects in the formed ZnIn_(2)S_(4) MFs,which could enhance both the separation and migration processes of the photoinduced charge-carriers due to the existence of discrete defect energy-levels(DELs) and the reduced effective mass of electrons,as evidenced by the first-principles calculations and the electron spectra analyses.The ZnIn_(2)S_(4) MFs with the optimal content of S-vacancy obtained by a hydrothermal treatment of the precursors with the Zn/In/S stoichiometric ratio of 1:2:8 possessed the long-lived photoinduced electron(~94.64 ns) for contributing to the photo-physical and-chemical processes.Thus,upon visible light irradiation,the H_(2)-evolution rate of this sample reached ~2.40 mmol h^(-1) g^(-1) with an apparent quantum efficiency of ~0.16% at 420 nm even though only using 5 mg of photocatalysts without any cocatalysts.

Effects of shape and particle size on the photocatalytic kinetics and mechanism of nano-CeO_(2)

Nanomaterials have been widely applied to many fields because of their excellent photocatalytic performance.The performance is closely related to the catalytic kinetics,but it is not completely clear about the influencing regularities of shape and particle size on the photocatalytic kinetics of nanomaterials and the photocatalytic kinetic mechanism.In this paper,nano-CeO_(2)with different shapes and particle sizes were prepared,the kinetic parameters of adsorption and photocatalytic degradation were determined,and the effects of shape and particle size on the kinetics of adsorption and photocatalysis and photocatalytic mechanism were discussed.The results show that the shape and particle size have significant influences.With the decreases of diameter,the performances of adsorption and photocatalysis of nano-CeO_(2)are improved;and these performances of spherical nano-CeO_(2)are greater than those of linear nano-CeO_(2).The shape and particle size have no effects on the kinetic order and mechanism of the whole photocatalytic process.Then a generalized mechanism of photocatalytic kinetics of nanomaterials was proposed and the mechanism rate equation was derived.Finally,the conclusion can be drawn:the desorption of photodegradation products is the control step of photocatalytic kinetics,and the kinetic order of photocatalytic degradation reaction is 1.The mechanism is universal and all nanomaterials have the same photocatalytic kinetic mechanism and order.

Kinetics of Photocatalytic Degradation of Formic Acid over Silica Composite Films Based on Polyoxometalates

The composite films, XW11O39n-/SiO2, (X refers to Si, Ge or P, respectively) were prepared by tetraethoxysilane (TEOS) hydrolysis sol-gel method via spin-coating technique. Formation of the composite films is due to strong chemical reaction of organic silanol group with the surface oxygen atoms of XW11O39n-, resulted in the saturation of the surface of the lacunary polyoxometalates (POMs). Therefore, the coordination structural model of the films was proposed. As for the films, retention of the primary Keggin structure was confirmed by UV-vis, FT-IR spectra and MAS NMR. The surface morphology of the films was characterized by SEM, indicating that the film surface is relatively uniform, and the layer thickness is in the range of 250~350 nm. Aqueous formic acid (FA) (0-20 mmol/L) was degraded into CO2 and H2O by irradiating the films in the near-UV area. The results show that all the films have photocatalytic activities and the degradation reaction follows Langmuir-Hinshelwood first order kinetics.

Photocatalysis of Naphthenic Acids in Water

Naphthenic acids (NAs) are soluble in water and are concentrated in oil sand process water (OSPW) as a result of caustic oil sands extraction processes. Significant environmental and regulatory attention has been focused on the naphthenic acids. A laboratory scale photocatalysis system was developed using UV254 florescent lamps. Experiments were conducted to determine the NA degradation efficiency of this system in presence of TiO2 catalyst. Degradation kinetics for total NAs as well as individual z-families was calculated. The developed treatment system was able to degrade OSPW NAs with half life values ranging between 1.55 and 4.80 h. This system also completely reduced the acute toxicity associated with NAs (up to 5 min. IC50 v/v > 90%) based on Microtox assays.

La、Co金属共掺杂TiO_(2)光催化材料的降解活性及动力学研究

为提高二氧化钛光催化降解效率,采用水热法合成了稀土La及过渡金属Co共掺杂的TiO_(2)复合光催化剂,并通过扫描电镜(SEM)、X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis DRS)等手段对材料进行了表征。以甲基橙和罗丹明B为模型污染物,研究La及Co共掺杂TiO_(2)光催化剂上催化降解活性,并对其催化降解动力学进行初步讨论。结果表明:水热法制得复合催化剂的形貌为球形结构,其中TiO_(2)为金红石相晶型,共掺杂后TiO_(2)的晶体结构未发生改变;La、Co共掺TiO_(2)复合材料的降解能力相比纯TiO_(2)有显著提高。当溶液浓度均取5 ppm时,1%(Co+La)/TiO_(2)催化剂上甲基橙溶液降解率为85.45%,1%(Co+La)/TiO_(2)催化剂上罗丹明B溶液降解率为94.56%。反应遵循Langmuir-Hinshelwood模型,具有一级反应动力学特征。

层状结构BiOBr的形成机理及其光催化降解抗生素性能

通过水热合成法片层结构溴氧化铋(BiOBr)颗粒,探究其形成机理,并在氙灯光照下以喹诺酮类抗生素诺氟沙星(NOR)为降解底物,考察BiOBr形貌结构变化对光催化性能的影响。X射线衍射(XRD)和扫描电子显微镜(SEM)分析确认BiOBr制备成功。结果表明,水热合成条件下制备的BiOBr为片层结构,随反应溶液pH值的增加,颗粒尺寸逐渐变小,且分散性越来越差,吸收带边发生蓝移,禁带宽度变大。分析水溶剂环境下片层BiOBr的形貌变化生长机理,当pH=1时,BiOBr形貌为均匀的片状结构,宽度为(3~5)μm,禁带宽度为2.93 eV,表现出最佳的光催化活性,光催化反应60 min后,NOR的降解率达到87.2%,最高降解速率常数为3.31×10^(-2)min^(-1)。

Highly selective and efficient photocatalytic NO removal:Charge carrier kinetics and interface molecular process

The widespread nitrogen oxides(NOx,mainly in NO)in the atmosphere have threatened human health and ecological environment.The dilute NO(ppb)is difficult to efficiently remove via the traditional process due to its characteristics of low concentration,wide range,large total amount,etc.Photocatalysis can utilize solar energy to purify NO pollutants under mild conditions,but its application is limited due to the low selectivity of nitrate and poor activity of NO removal.The underlying reason is that the interface mechanism of NO oxidation is not clearly understood,which leads to the inability to accurately regulate the NO oxidation process.Herein,the recent advances in the photocatalytic oxidation of NO are summarized.Firstly,the common strategies to effectively regulate carrier dynamics such as morphology control,facet engineering,defect engineering,plasma coupling,heterojunction and single-atom catalysts are discussed.Secondly,the progress of enhancing the adsorption and activation of reactants such as NO and O_(2) during NO oxidation is described in detail,and the corresponding NO oxidation mechanisms are enumerated.Finally,the challenges and prospects of photocatalytic NO oxidation are presented in term of nanotechnology for air pollution control.This review can shed light on the interface mechanism of NO oxidation and provide illuminating information on designing novel catalysts for efficient NOx control.

CuO/BiOCl异质结催化剂的合成及其光催化性能研究

以微球状氯氧化铋(BiOCl)为模板,合成了CuO/BiOCl异质结催化剂,利用扫描电子显微镜、X射线衍射仪、荧光分光光度计等对催化剂形貌和结构进行了表征;以亚甲基蓝(MB)为降解目标,探究了CuO与BiOCl物质的量比、MB染料初始质量浓度、催化剂质量、溶液pH等对CuO/BiOCl催化性能的影响,并研究了该催化剂的循环再生能力及光催化反应机理。结果表明:在可见光照射下,当CuO与BiOCl物质的量比为1∶15,催化剂质量为0.050g,MB初始质量浓度为25mg/L时,光催化效率最高,吸附过程符合一级动力学模型,且该催化剂具有良好的循环再生能力。在催化过程中空穴h+起主要作用,羟基自由基和超氧自由基均起次要作用。

Kinetic Modeling of the Photocatalytic Degradation of Methyl Orange by Supported TiO2

The photocatalytic degradation of methyl orange （MO） in UV/Supported-TiO2 system was investigated and a kinetic model was presented. The experimental results show that the photocatalytic degradation rate is favored by high concentration of dye in solution and is enhanced by the solution temperature. A simple kinetic model has been proposed which can describe the discoloration process in an adequate way. The calculated results obtained were in good agreement with experimental data. The model predicts the concentration of MO during the photocatalytic degradation process.

白云母/TiO_(2)复合材料的制备及光催化性能

以钛酸丁酯为钛源、冰醋酸为抑制剂,通过水热法合成白云母/TiO_(2)(M/T)复合光催化材料。采用X射线衍射(XRD),拉曼光谱(Raman),扫描电子显微镜(SEM),能谱仪(EDS),N2吸附-脱附(BET),紫外-可见漫反射光谱(UV-Vis),荧光光谱(PL)对样品的物相结构、表面形貌、元素分布、孔隙结构及光学特性进行表征,并以甲基橙(MO)溶液为目标污染物,考察水热温度、水热时间、TiO_(2)负载量对M/T复合材料光催化性能的影响。结果表明:100℃水热16 h, TiO_(2)负载量为20%(质量分数)的M/T复合材料光催化性能最好;紫外光照射60 min,对MO的降解率达到99.62%,总有机碳(TOC)去除率为63.58%,重复使用5次,光催化活性没有明显降低,且M/T复合材料光降解MO过程符合一级反应动力学模型,最大反应速率常数kapp为0.049 min^(-1)。

乙二醇条件下球状结构BiOBr的形成机理及光催化性能研究

采用乙二醇溶剂热法制备了球状结构的溴氧化铋(BiOBr),通过X射线衍射(XRD)、扫描电镜(SEM)和紫外-可见漫反射光谱(UV-Vis DRS)等技术方法对样品进行了表征分析,探究了其形成机理,并在氙灯光照下以诺氟沙星(NOR)为降解底物,探讨了结构变化对BiOBr光催化性能的影响。结果表明:乙二醇条件下制备的BiOBr为球状结构,随反应溶液pH的增加,尺寸逐渐变小,且分散性越来越差,吸收带边发生蓝移,禁带宽度变大。得出了乙二醇溶剂环境下球状BiOBr的生长机理,并证明当pH为3时,制备的BiOBr-e3样品形貌为均匀的球状结构,直径为5μm左右,禁带宽度为2.71eV,表现出最佳的光催化活性。

Continuous microflow visible-light photocatalytic N-formylation of piperidine and its kinetic study

N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency.Here,an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine,which achieved a reaction yield of 82.97%and a selectivity of>99%at 12 min using cheap organic dye photocatalyst under mild reaction conditions.The influence of essential parameters,including light intensity,temperature and equivalents of the gas,additive and photocatalyst,on the reaction yield was systematically studied.Furthermore,kinetic investigations were conducted,exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity,temperature and photocatalyst equivalent.The microflow photocatalytic approach established in this work,which realized a markedly higher space-time yield than the conventional batch method(37.9 vs.0.212 mmol h-1 L-1),paves the way for the continuous,green and efficient synthesis of N-formamides.

TiO_2光催化反应机理及动力学研究进展

光催化处理环境污染物是基于催化反应过程中的一些自由基对污染物的氧化或还原作用 ,反应途径通常是 HO·攻击或空穴直接攻击 ,对可见光敏感的化合物也可能通过激发态来分解。动力学的表述多数符合 L- H模式 ,广泛研究了 L- H模式下的吸附与催化活性的关系 。

偶氮染料吸附和光催化氧化动力学

以甲基橙和酸性大红两种偶氮染料为模拟污染有机物,对它们的暗吸附和光催化氧化行为进行研究.实验结果表明,两种偶氮染料的吸附受溶液酸碱度影响很大,酸性(pH=3)条件下,两种染料吸附量都很大,酸性大红吸附量更大;近中性(pH≈6)时两种染料的吸附显著减少;碱性(pH=9)条件下两种染料不发生吸附.光催化反应结果显示,碱性条件或酸性条件下两种染料降解速度都很快.说明在不同酸碱度条件下,光催化反应按不同机理进行.酸性条件下,反应在催化剂表面进行,在碱性介质中,光催化氧化在溶液中进行.提出了一个碱性条件下的动力学方程,经过进一步简化,可以得到表观一级方程,形式上和准一级L-H方程十分相似,但其含义不同.

部分水溶性偶氮染料的光催化降解研究

本研究以高压汞灯为光源,系统地研究了16种偶氮染料在水溶液中的TiO_2光催化降解,结果表明,这些偶氮染料的光解为一级动力学反应,采用TiO_2光催化降解方法处理所研究的偶氮染料是可行的,井初步探讨了染料的结构与光解反应表观速率常数之间的关系。

掺铁二氧化钛为催化剂光催化氧化汽油气研究

采用溶胶 -凝胶法制备了掺铁TiO2 催化剂薄膜 ,并用其光催化处理汽油废气 .考察了不同掺铁比的TiO2 薄膜光催化降解汽油气的效果 ,确定TiO2 最佳掺铁比为wFe 为 0 .16 6 .探讨了光催化氧化过程中相对湿度对汽油降解的影响 ,结果表明 ,湿度对光催化降解汽油气影响很大反应体系中最佳相对湿度为 30 % .对光催化氧化降解汽油气动力学进行了探讨 。

气相甲苯光催化降解反应动力学及机理

以紫外光为光源,锐钛矿型TiO2为催化剂,研究了气相甲苯光催化降解过程,并探讨了降解机理.结果表明,甲苯光催化降解过程符合一级反应动力学方程,甲苯初始浓度越高,反应速率常数越小.甲苯光催化降解的主要中间产物为己烷和苯.在紫外光和TiO2作用下,甲苯经脱甲基反应生成苯和甲基,甲基可与甲苯分解产生的3-戊烯炔生成2,4-己二烯,经加氢转化为己烷.