Ag_2CO_3/BiVO_4复合微米片光催化剂的制备、表征及光催化机理

采用水热法制备粒径为1~2μm的BiVO_4微米片,然后在微米片表面沉积不同含量的Ag_2CO_3颗粒,制备Ag_2CO_3/BiVO_4复合微米片光催化剂。利用X射线粉末衍射(XRD)、扫描电镜(SEM)、红外光谱(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光(PL)光谱、瞬态光电流-时间响应对催化剂进行表征。以可见光为光源,罗丹明B为降解对象进行光催化活性测试。结果表明,复合适量Ag_2CO_3有利于提高光催化剂的比表面积,改善催化剂的表面性能。活性测试结果表明,当复合10%(w/w)Ag_2CO_3时,Ag_2CO_3/BiVO_4光催化活性最佳,比纯BiVO_4提高4.4倍。光致发光(PL)光谱、瞬态光电流-时间响应测试结果表明,复合Ag_2CO_3能有效抑制光生电子与空穴的复合。自由基捕获实验结果表明,该体系的活性氧物质为空穴和羟基自由基。Ag_2CO_3/BiVO_4复合光催化剂活性提高的原因,是较宽带隙的Ag_2CO_3与较窄带隙的BiVO_4形成的异质结有效抑制了光生电子与空穴的复合,同时两者适宜的能带结构保证产生更多的空穴,从而具有更强的氧化能力。     

BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂的制备及光催化性能研究

以Bi(NO_3)_3·5H_2O和NH_4VO_3为原料,控制水溶液介质p H及反应时间,采用水热合成法制备钒酸铋(BiVO_4)及其复合物(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3).利用X-射线粉末衍射、扫描电子显微镜和紫外-可见漫反射吸收光谱等手段对制备的样品进行了物理表征,结果表明,在控制反应时间为1 h,介质p H值在1.14~9.01之间时,制备的样品为BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合物,当p H值增加至10.92时为纯BiVO_4;控制介质p H为7.17,反应时间在1~12 h之间时得到BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂,反应时间为18 h时为纯BiVO_4.在可见光(λ≥400 nm)照射下,以有机染料罗丹明B(Rhodamine B,Rh B)为底物,研究不同条件制备的BiVO_4或者复合物为光催化剂的光催化特性,发现p H=7.17,水热反应12 h得到的催化剂(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3)光催化降解活性高于对照制备的纯BiVO_4.同时在可见光照射下,BiVO_4/Bi_6O_6(OH)_3(NO_3)_3亦可以有效降解无色小分子2,4-二氯苯酚(2,4-Dichlorophenol,2,4-DCP),说明氧化过程涉及到光催化过程.分析BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂对Rh B光催化降解过程中活性物种,表明在降解过程中主要涉及空穴和超氧氧化,O_2·~-起主要作用.     

BiVO_4/MOF复合材料的合成及其光催化性能

通过简单溶剂热法制备了一种新型复合光催化剂BiVO_4/M IL-53(Fe);运用XRD、SEM/EDS、FT-IR、N_2吸附-脱附和UV-vis DRS等手段对其进行表征,并对其光催化降解RhB活性进行了研究,提出了相应的光催化降解RhB的可能机理。结果表明,相较于单一BiVO_4材料,复合催化剂的比表面积增大,且其光催化效率相较于纯BiVO_4和MIL-53(Fe)也有了较大的提高;其中,BF-2复合材料的光催化活性最高,分别约为纯MIL-53 (Fe)和BiVO_4的5. 2倍和8. 1倍。同时,BiVO_4/MIL-53(Fe)复合光催化剂经过四次循环实验后,仍能保持较稳定的光催化活性和结构。     

一锅法合成在可见光下具有高效降解草甘膦的牡丹状Bi2S3/BiVO4(040)复合光催化剂

草甘膦是一种广谱除草剂, 2015年世界卫生组织国际癌症研究机构宣布草甘膦可能对人类致癌(2A类).单斜白钨矿型BiVO_4是一种较广泛研究的可见光光催化剂,但由于其光生电子和空穴迁移慢且容易复合而导致其光催化活性低.此外,有研究表明, BiVO_4的(040)晶面易于光生载流子分离,从而提高其光催化性能.Bi_2S_3的带隙能为1.27 eV,能被全可见光(400-800 nm)激发.Bi_2S_3的导带和价带位置与BiVO_4匹配,能形成异质结,从而提高其光催化活性.本文以EDTA为导向剂, L-半胱氨酸为硫源和软模板,采用一锅水热法制备了单斜白钨矿型BiVO_4,主要以(040)晶面为暴露面的Bi_2S_3/BiVO_4复合光催化剂.采用钼锑抗分光光度法测定草甘膦最终光催化降解产物之一PO_4~(3-)浓度,来计算草甘膦的降解率.X射线衍射(XRD)结果表明, Bi_2S_3/BiVO_4复合光催化剂只含Bi_2S_3和BiVO_4两种成分,没有其他晶相存在.场发射扫描电子显微镜(FESEM)显示,纯BiVO_4为片状结构,随着Bi_2S_3复合量增加, Bi_2S_3/BiVO_4的形貌为小片组成的牡丹状;但Bi_2S_3复合量进一步增加, Bi_2S_3/BiVO_4颗粒聚集严重.XRD, FESEM和高分辨透射电子显微镜(HRTEM)结果表明, Bi_2S_3复合量对Bi_2S_3/BiVO4样品(040)和(121)面晶生长及形貌有显著影响.Bi_2S_3的复合提高了Bi_2S_3/BiVO_4对可见光的吸收能力,经计算BiVO_4和Bi_2S_3带隙能分别为2.42和1.27 eV.随着Bi_2S_3复合量增加, Bi_2S_3/BiVO_4的光催化活性逐渐提高,至1 mmol时最高,对草甘膦的降解率为纯BiVO_4的2.2倍;但随着Bi2S3复合量进一步增加, Bi_2S_3/BiVO_4的光催化活性反而下降,可能是由于Bi_2S_3量太多包覆在BiVO_4表面而Bi_2S_3光催化性能很差的缘故.瞬态光电流测试和电化学阻抗谱的结果证实, Bi_2S_3/BiVO_4比BiVO_4具有更有效的电荷分离和更快的界面电荷转移能力.活性成分捕获剂实验表明,加入空穴捕获剂EDTA或电子捕获剂K_2Cr_2O_7完全抑制了草甘膦的降解.ESR谱证明羟基自由基·OH的存在.通过计算,得出BiVO_4的价带电位(EVB=2.87 eV vs. NHE)比Bi_2S_3 (EVB=1.69 eV vs. NHE)正,而Bi_2S_3 (EVB=0.42 eV vs. NHE)的导带电位比BiVO_4 (EVB=0.45 eV vs. NHE)负,能带匹配,即光生电子从Bi2S3迁移至Bi VO4,光生空穴从BiVO_4迁移至Bi_2S_3,从而将光生电子与空穴有效分离利用,达到提高其光催化性能的目的.Bi_2S_3/BiVO_4样品对草甘膦的光催化降解活性提高,主要是由于Bi_2S_3/BiVO_4异质结结构的形成提高了其对可见光的吸收能力和电子空穴对的分离效率.此外, Bi_2S_3/BiVO_4具有相对稳定性和可重复使用性.该方法简单,可制备用于光催化降解有机污染、光催化裂解水和光催化还原二氧化碳等不同领域的高活性复合光催化剂.     

光系统II杂化Z型水分解体系中产氢助催化剂上逆反应的抑制

光催化Z型水分解反应有望发展成为一种生产太阳氢能的有效方法.将具有优异水氧化性能的自然光系统Ⅱ与人工半导体产氢材料进行耦合,以构建生物-人工杂化光催化Z型水分解反应体系,对于深入理解自然光合作用原理和促进人工太阳能转化具有重要意义.由于Fe(CN)_6~(3-)可从光系统Ⅱ接受电子,因此氧化还原电对Fe(CN)_6~(3-/4-)成为研究光系统Ⅱ基杂化Z型水分解体系时常用的电子体递.然而,在该Z型水分解反应中,正向的产氢反应经常受到由Fe(CN)_6~(3-)引起的逆反应的阻碍,致使水分解过程中产氢产氧失衡,不能实现有效的全分解水反应.本文通过在光系统Ⅱ杂化Z型水分解体系中的人工光催化剂ZrO_2/TaON上沉积产氢助催化剂PtCrOx,有效抑制了逆反应的发生,从而使体系实现了全分解水反应.实验发现,在光催化剂ZrO_2/TaON上沉积金属Pt作为产氢助催化剂时,以Fe(CN)_6~(4-)为电子供体的光催化产氢半反应基本没有产氢活性,而当沉积氧化物PtCrO_x作为产氢助催化剂时,产氢半反应活性可提高至～35μmolh–1.进一步研究发现,这种产氢活性的差异主要是由于两种不同助催化剂对于Fe(CN)_6~(3-)引起的氢气氧化逆反应的催化行为不同.金属Pt表面对于氢气具有吸附和活化作用,光催化反应中产生的氢气和Fe(CN)_6~(3-)在Pt-ZrO_2/TaON催化作用下发生快速的氧化还原逆反应;而由于PtCrO_x表面对氢气的吸附和活化作用较弱,上述氢气氧化的逆反应在PtCrO_x-ZrO_2/TaON存在时不发生.此外,在产氢过程中,光生电子虽然迁移到助催化剂PtCrO_x上,但PtCrO_x中高氧化态的Pt~Ⅱ和Pt~Ⅳ并未被还原,因此使PtCrO_x-ZrO_2/TaON具有稳定的光催化产氢反应活性.基于PtCrO_x-ZrO_2/TaON在Fe(CN)_6~(4-)作为电子供体时有效的产氢半反应,我们以Fe(CN)_6~(3-/4–)作为电子递体,将光系统Ⅱ与PtCrOx-ZrO_2/TaON耦合构建了生物-人工杂化Z型全分解水体系,通过调节Fe(CN)_6~(3-)/4–的初始浓度,最终实现了杂化体系的全分解水反应,产氢和产氧活性分别为～20μmol H_2 h~(–1)和～10μmol O_2 h~(–1).这为理解和抑制以Fe(CN)_6~(3-)/4–作为电子递体的光系统Ⅱ-人工杂化Z型水分解体系中的逆反应提供了新的思路.     

NiFe双氢纳米粒子有效提高BiVO_4光阳极光电化学水分解性能（英文）

近年来,太阳能驱动的光电化学水分解作为一种高效、环保、可持续的技术,已经引起了广泛的关注.为了更好地使用光电化学技术将太阳能转化为化学能,至关重要的是提高光电极材料的光吸收和光转化效率.BiVO_4禁带宽度(Eg=2.4–2.5 eV)小,具有很好的可见光响应能力,因此BiVO_4光电极材料引起了广泛关注.但是,当单独BiVO_4作为光电阳极材料时,电子-空穴对分离弱、载流子传输慢,从而使BiVO_4不能很好地在光电化学水分解中发挥作用.为了缓解或解决此类限制性因素,本课题组通过水热法合成了NiFe双氢纳米粒子,并将其负载于BiVO_4电极表面,光电催化分解水实验表明其产氢效率得到大幅度提高.同时制备了Ni(OH)_2/BiVO_4和Fe(OH)2/BiVO_4电极并用于研究NiFe/BiVO_4电极的反应机理.在上文基础上,本文采用电子扫描电镜(SEM)、高分辨投射电镜(HRTEM)、X射线衍射(XRD)、紫外可见漫反射(UV-Vis DRS)等表征手段和线性扫描伏安法(LSV)和电流时间(I-t)等对其光电化学活性进行了测试,研究了NiFe/BiVO_4电极在发生水氧化时的反应机理.SEM结果表明,Ni(OH)_2是以纳米片组成的纳米球负载于多孔BiVO_4表面;而当Fe(OH)2负载于BiVO_4表面时,BiVO_4的纳米尺寸减小;NiFe-LDH纳米粒子负载于BiVO_4表面时,可以明显看见BiVO_4纳米颗粒表面包裹着一层更小的纳米粒子.这证明了Ni(OH)_2,Fe(OH)2和NiFe-LDH纳米粒子均成功负载于BiVO_4表面.这也得到HRTEM结果的确认.UV-Vis DRS结果表明NiFe-LDH纳米粒子能有效拓宽BiVO_4的吸收边,从而增加对可见光的吸收,增加了对光的利用率.LSV测试结果表明,暗反应条件下Ni(OH)_2/BiVO_4比NiFe/BiVO_4和Fe(OH)2/BiVO_4电极的起始电位更低,说明Ni(OH)_2有更好的传输电子性能;而在光照条件下,在同一电位时NiFe/BiVO_4比Ni(OH)_2/BiVO_4和Fe(OH)2/BiVO_4电极的光电流值更高.值得注意的是,此时Ni(OH)_2/BiVO_4比Fe(OH)2/BiVO_4电极的光电流值低,这又说明Fe(OH)2比Ni(OH)_2对光更敏感.因此当NiFe-LDH纳米粒子负载于BiVO_4表面时,不仅提高了BiVO_4光电极的光吸收效率,而且加速了载流子的传输从而抑制了光生电子-空穴的复合,使反应过程中的量子效率得到提高     

二氧化锰/钒酸铋复合光催化剂的制备及性能

采用液相沉淀法制备了不同锰含量的二氧化锰(MnO_2)/钒酸铋(BiVO_4)复合光催化剂,利用XRD、SEM、XPS等对催化剂进行了表征。通过对罗丹明B的降解,研究了不同锰含量的光催化剂在太阳光下的光催化降解性能,并考察了催化剂用量对光降解率的影响。结果表明,制备出的不同Mn含量的BiVO_4光催化剂均为单斜晶型结构,且Mn元素是以MnO_2的形式存在,说明Mn元素的引入没有改变BiVO_4的晶型和结构。其中Mn含量为1.67%的BiVO_4样品具有最高的光催化活性,光催化反应90 min对罗丹明B溶液的降解率可达到26.39%,比纯BiVO_4样品的降解率(14.06%)提高了近一倍,其催化性能提高的原因可能是由于一定量MnO_2的存在使催化剂中光生电子-空穴的高效分离造成的。同时发现当MnO_2的含量过高,由于形貌分布不均,会变成光生电子和空穴的复合中心,致使催化剂的活性降低。不同用量的同种催化剂光降解实验结果表明:对罗丹明B的光降解率随催化剂用量的增加而增大,但超过一定用量后,光降解率增加速度变缓。     

四角星形BiVO4/Bi2O3催化剂的制备及性能

采用水热法合成具有四角星形貌的钒酸铋,再将钒酸铋浸渍在碱溶液里二次水热,制备出BiVO_4/Bi_2O_3催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM),紫外-可见漫反射(UV-Vis DRS)等方法对样品进行表征。可见光下,BiVO_4/Bi_2O_3复合物的光催化降解罗丹明B性能及光电流响应均优于纯BiVO_4。这是由于BiVO_4/Bi_2O_3复合材料形成了异质结构,有效抑制了光生电子与空穴的复合效率。     

非贵金属助催化剂Ni3N修饰g-C3N4用于可见光催化产氢的研究

近年来,利用太阳光光解水制氢被认为是解决当前能源短缺和环境污染问题的重要途径之一.众所周知,助催化剂可以有效的降低光催化产氢反应的活化能,提供产氢反应的活性位点,有效的促进催化剂中光生载流子的传输与分离,从而提高光催化剂产氢体系的反应活性和稳定性.然而,鉴于贵金属助催化剂(Pt, Au和Pd等)储量低、成本高,极大地制约了其应用.因而,开发出适用于光催化水分解制氢的非贵金属助催化剂尤为重要.石墨相氮化碳(g-C_3N_4)因其具有热稳定性、化学稳定性高以及制备成本低廉等优点,成为光催化领域研究的热点.然而,由于g-C_3N_4的禁带宽度(Eg=2.7 eV)较宽,致使其对可见光的响应能力较弱,并且在光催化反应过程中其光生电子-空穴对易复合,从而导致其光催化产氢活性较低.因此,如何开发出含非贵金属助催化剂的g-C_3N_4高效、稳定的太阳光催化分解水制氢体系引起了人们极大的关注.本文通过水热法-高温氨化法首次将非贵金属Ni_3N作为助催化剂来修饰g-C_3N_4,增强其可见光光催化性能(l420 nm).采用XRD、SEM、EDS、Mapping、UV-Vis、XPS和TEM等手段对Ni_3N/g-C_3N_4光催化体系进行了表征.结果表明, Ni_3N纳米颗粒成功的负载到g-C_3N_4表面且没有改变g-C_3N_4的层状结构.此外,采用荧光光谱分析(PL)、阻抗测试(EIS)和光电流谱进行表征,结果显示, Ni_3N纳米颗粒可有效促进催化剂中光生载流子的传输与分离,抑制电子-空穴对的复合.同时,将功率为300 W且装有紫外滤光片(λ420 nm)的氙灯作为可见光光源进行光催化产氢实验结果表明,引入了一定量的Ni_3N可以极大提高g-C_3N_4的光催化活性,其中, Ni_3N/g-C_3N_4#3的产氢量为～305.4μmol·h-1·g-1,大约是单体g-C_3N_4的3倍.此外,在450nm单色光照射下, Ni_3N/g-C_3N_4光催化产氢体系的量子效率能达到～0.45%,表明Ni_3N/g-C_3N_4具有将入射电子转化为氢气的能力.循环产氢实验表明, Ni_3N/g-C_3N_4在光催化产氢过程中有着较好的产氢活性和稳定性.最后,阐述了Ni_3N/g-C_3N_4体系的光催化产氢反应机理.本文采用的原料价格低廉,性能优异,制备简单,所制材料在光催化制氢领域展现出重要前景.     

三维花状Ni(OH)2包裹TiO2微米球用于光催化产氢

TiO_2具有合适的能带位置以及成本低、无毒、稳定性高等优点,但由于大的激子结合能(130 meV)以及电子-空穴复合严重,其光催化性能和效率较低.目前,负载助催化剂是一种比较有效的提高TiO_2光催化效率的方法.助催化剂可通过抑制电子与空穴的复合、降低激子结合能、提高界面电子传输速率来提高光催化性能.寻求新型、廉价、高效产氢的助催化剂是当前光催化研究的热点.近年来, Ni(OH)_2由于具有多变的形貌以及一定的光催化性能而被人们关注.并且Ni(OH)_2本身就是p型光催化剂,可与主体材料复合形成p-n异质结材料,其中由异质结形成的内建电场可起到促进电子与空穴分离的作用.基于此,本文采用简单的合成方法制备出新颖的三维花状Ni(OH)_2包裹TiO_2纳米结构微球,通过X射线衍射仪(XRD)、扫描电镜(SEM)和透射电镜(TEM)等表征手段确定了目标产物被成功合成,并采用光催化产氢为探针反应研究了其光催化性能.结果表明, Ni(OH)_2包裹TiO_2纳米材料的产氢速率比纯TiO_2纳米材料提高了5倍.通过紫外-可见漫反射吸收光谱(DRS)与一系列对比实验发现, Ni(OH)_2拓宽了TiO_2的吸收光谱范围,催化活性的提高确实来源于引入的Ni(OH)_2.氮气吸脱附等温线和孔径分布分析表明, Ni(OH)_2壳的引入增大了催化剂的比表面积并且带来介孔,证实三维花状的纳米片界面为光催化产氢提供了更多的活性位点.电化学表征结果进一步证明,这种独特的p-n异质结促进了电子与空穴的分离和转移.基于元素分析和产氢活性结果,我们提出了可能的反应机理.     

Combination of visible-light responsive heterogeneous and homogeneous photocatalysts for water oxidation

Bismuth vanadate (BiVO(4)), which is a visible-light responsive heterogeneous photocatalyst, was combined with homogeneous ruthenium complexes to increase the overall photocatalytic reactivity for water oxidation with a one-electron oxidant, [Co(III)(NH(3))(5)Cl](2+). Photoinduced electron transfer from the excited state of ruthenium(II) complexes to [Co(III)(NH(3))(5)Cl](2+) affords ruthenium(III) complexes which can oxidize water to oxygen with BiVO(4) under visible light irradiation.     

硅烷基Schiff碱共价修饰纳米二氧化硅负载过渡金属催化乙烯齐聚性能

将3种水杨醛Schiff亚胺配合过渡金属（Si-Schiff-M,M=Ni,Co,Cr）通过共价键接枝到纳米二氧化硅,制备了3种硅烷基Schiff碱共价修饰纳米二氧化硅负载过渡金属催化剂（Si-Schiff-SiO₂-M）,并对其催化乙烯齐聚性能进行了研究;采用元素分析、红外光谱、扫描电子显微镜和电感耦合等离子色谱表征了3种Si-Schiff-SiO₂-M的结构和形貌。以甲基铝氧烷（MAO）为助催化剂,研究了反应条件及催化活性中心种类对3种Si-Schiff-SiO₂-M催化乙烯齐聚产物性能的影响。结果表明,当Si-Schiff-SiO₂-M用量为7 μmol, n（Al）/n（M）（M=Cr,Ni,Co）为500,反应温度为35 ℃,反应压力为0.5 MPa和反应时间为30 min时, Si-Schiff-SiO₂-Cr、Si-Schiff-SiO₂-Ni和Si-Schiff-SiO₂-Co催化乙烯齐聚活性分别为1.92×10⁵ g/（mol Cr·h）、2.17×10⁵ g/（mol Ni·h）和2.07×10⁵ g/（mol Co·h）,且3种催化剂催化乙烯齐聚产物主要是C4和C6烯烃。Si-Schiff-SiO₂-M由于载体的限域效应,其催化乙烯齐聚活性低于相应的均相催化剂（Si-Schiff-M）,但产物分布较均相催化剂窄。Si-Schiff-SiO₂-M具有良好的循环利用性,3次循环使用后,3种负载型催化剂催化乙烯齐聚活性分别为1.39×10⁵ g/（mol Cr·h）、1.68×10⁵ g/（mol Ni·h）和1.42×10⁵ g/（mol Co·h）。     

Synthesis of Holey Graphitic Carbon Nitride with Highly Enhanced Photocatalytic Reduction Activity via Melamine-cyanuric Acid Precursor Route

In this work, holey graphitic carbon nitride(HCN) was prepared by one-step thermal polymerization of hydrothermal product of melamine and then loaded with Ni/MoO₂(NiMo) cocatalyst obtained by NaBH₄ reduction process. The obtained material was used for photocatalytic production of H₂ from water reduction and H₂O₂ production from O₂ reduction. The best photocatalyst(1% NiMo/HCN) exhibited a H₂ evolution rate of 8.08 μmol/h while no H₂ was detected over 1% NiMo-modifed bulk g-C₃N₄(BCN) under visible light illumination. Moreover, this rate is 1.7 times higher than that of 1% Pt-modified HCN. The 1% NiMo/HCN catalyst also exhibited the highest H₂O₂ production activity with a value of 6.13 μmol/h. Such enhancement was ascribed to the efficient charge carrier separation and migration, which were promoted by the large specific surface area and pore volume of HCN and the synergy between MoO₂ and Ni. The proposed method to obtain HCN is expected to open up new ways in development of highly-active HCN-based photocatalysts for photocatalytic reduction reactions.     

Efficient visible-light photocatalytic water splitting by minute amounts of gold supported on nanoparticulate CeO2 obtained by a biopolymer templating method

When irradiated with visible light (λ > 400 nm) 1 wt % gold-supported ceria nanoparticles generate oxygen from water (10.5 μmol·h(-1)) more efficiently than the standard WO(3) (1.7 μmol·h(-1)) even under UV irradiation (9.5 μmol·h(-1)). This remarkable photocatalytic activity arises from a novel preparation method to reduce the particle size of ceria (5 nm) by means of electrostatic binding of Ce(4+) to alginate gel, subsequent supercritical CO(2) drying, and calcination. The low loading of Au is crucial for the observed high catalytic activity.     

银纳米粒子沉积含有氧空位的钒酸铋能够提高其近红外光催化性能（英文）

钒酸铋因其独有的廉价、低毒性、热稳定性和高氧化性能等特性而备受瞩目,是利用太阳能降解污染物、水分解等应用方面最优选择的半导体纳米材料之一.选择表面粗糙多孔尺寸均匀的橄榄状钒酸铋有助于吸附更多的电子受体参与到半导体表面的氧化还原反应当中,从而提高其光催化活性.另外,太阳能谱中紫外光占不到5%,可见光占45%,与传统的半导体TiO_2材料相比,钒酸铋禁带宽度在2.4 eV左右,能较好地吸收太阳光能实现光能转化.但是太阳光中近一半的光能属于近红外,不能被传统的纯相钒酸铋所利用.为了更好地利用太阳能,可将氧空位缺陷引入到钒酸铋晶体中,以实现近红外光能的转化利用.氧空位缺陷在半导体材料中不仅能够吸收近红外光,在低于导带的位置形成电子传输的桥梁,而且能够吸附更多的氧分子转化成活性物种.另一方面,氧空位缺陷态的引入使半导体钒酸铋材料暴露更多的活性位点,参与到溶液的氧化还原反应中.由于钒酸铋光激发的载流子浓度有限,并且光生电子-空穴容易复合,本文采用银纳米粒子负载在钒酸铋表面,利用其等离子共振效应产生的热电子与氧空位缺陷的协同作用,能够提高其载流子传输速率,抑制光生电子-空穴复合,达到更优的光能到化学能转化的目的.基于此,本文采用电子自旋共振光谱(ESR),X射线光电子能谱(XPS)和紫外可见光谱(UV-Vis)等手段研究了氧空位缺陷引入到钒酸铋以及Ag纳米粒子担载于橄榄状半导体材料上对光催化降解罗丹明B染料中太阳能驱动活性的影响.ESR结果证明,在测试过程中橄榄状钒酸铋材料吸收了更多的电子,表明存在很多氧空位缺陷.XPS结果表明出现高浓度的吸收氧峰意味着钒酸铋材料上存在大量氧空位缺陷;银纳米粒子成功负载在具有氧空位缺陷的钒酸铋材料上.UV-Vis结果表明该材料光吸收范围扩展到近红外光范围,其禁带宽度比传统纯相钒酸铋减小,Ag-BiVO_4-OV样品的导价带位置发生明显变化.因此,由于氧空位和银纳米粒子存在于橄榄状钒酸铋主体中,其光催化降解罗丹明B的效率远远高于纯相钒酸铋样品.由此可见氧空位缺陷和银纳米粒子的引入使得半导体光催化材料光学性能正效应增加.Supporting Information for Ag nanoparticles deposited on oxygen-vacancy-containing BiV O4 for enhanced near-infrared photocatalytic activity Chunjing Shi,Xiaoli Dong*,Xiuying Wang,Hongchao Ma,Xiufang Zhang School of Light Industry and Chemical Engineering,Dalian Polytechnic University,Dalian 116034,Liaoning,China*Corresponding author.E-mail:dongxl@dlpu.edu.cn On the other hand,the nitrogen sorption isotherm of the reactions,but also can provide more surface active sites for as-prepared samples possesses an obvious condensation step oxygen activation and reduction,and thereby positively around P/P0=0.5-0.9,which is typical hysteresis loops of facilitating the reaction process and endowing the catalyst with mesoporous materials(Fig.S1).It is indicated that the robust redox kinetics.as-prepared Ag-BiV O4-OV possesses the mesoporous structure To further prove remarkable photocatalytic activities of the(Fig.S2).In addition,the Ag-BiV O4-OV exhibits ultra-large as-prepared samples,the photocatalytic activities of the typical surface area(34.8 m3/g),which is more than 2 times larger samples based on previous report was listed(Table S1).This than that of pure BiV O4(Fig.S1).The novel mesoporous statistics indicated that the as-prepared Ag-BiV O4-OV reveals structure and larger surface area not only can promote the more excellent photocatalytic performance.diffusion of active species and accelerate subsequent surface50Ag-Bi VO-OV41)-g3m40(c d Bi VO4be30ords a20me u olV1000.0 0.2 0.4 0.6 0.8 1.0Relative pressure(P/P)0Fig.S1.N2-sorption isotherm of pure BiV O4 and Ag-BiV O4-OV.Ag-Bi VO4-OV Bi VO41)-mn1-g3m(c D d V/d0 10 20 30 40 50 60 70 80Pore size(nm)Fig.S2.Pore size distributions of pure BiV O4 and Ag-BiV O4-OV.Table S1Summary for the photocatalytic activities of the typical samples.Sample Amount Amount of dye Light source Time Degradation rate Reference Ag-BiV O4-OV 20 mg 50 mL RhB(10 mg/L)simulated sunlight 100 min 99%this work mono-dispersed m-BiV O4 0.1 g 50 mL RhB(15μmol/L)visible light 10 h 99%[1]BiV O4–Ag/Co3O4 100 mg 50 mL RhB(10 mg/L)simulated sunlight 120 min 97%[2]the BiV O-4 80 mg 80 mL RhB(1×105 mol/L)visible light 6 h 97%[3]Dy-BiV O4 50 mg 50 mL(10 mg/L)visible light 10 h 66.9%[4]m-BiV O4 0.2 g 100 mL of RhB(0.01 mmol/L)visible light 150 min 98%[5]BiV O4/CeO 2 50 mg 50 mL RhB(2×10-5 mol/L)visible light 210 min 90%[6]     

Cobalt-phosphate complexes catalyze the photoelectrochemical water oxidation of BiVO4 electrodes

BiVO(4) semiconductor electrodes were coupled with cobalt-phosphate complexes (CoPi) to enhance the photoelectrochemical (PEC) performance for water oxidation reaction. CoPi was deposited on a 550 nm-thick BiVO(4) film via electrodeposition (ED) and photodeposition (PD) methods for comparison of their effects. The CoPi on BiVO(4) exhibited Co?:?P atomic ratios of approximately 1?:?7 for the electrodeposited sample and approximately 1?:?18 for the photodeposited sample, and Co(2+) and Co(3+) co-existed in both samples. Optimized CoPi ED resulted in a CoPi overlayer of approximately 850 nm thick, which showed an electrochromic-like behavior that was likely due to limited access of phosphate into BiVO(4) across the CoPi layer. Optimized CoPi PD, however, had very thin and rather uniform CoPi dispersion and did not show electrochromic-like behavior. Despite the lesser amount of CoPi, the PEC performance of BiVO(4)/CoPi (PD) was comparable to that of BiVO(4)/CoPi (ED). Real-time measurements of the headspace molecular oxygen that evolved from water oxidation indicated that CoPi enhances O(2) production and photocurrent generation at BiVO(4) by a factor of around 15 and a maximum of 20, respectively, at 0.576 V(SCE) (equivalent to 1.23 V(RHE)) under air mass 1.5 irradiation (400 mW cm(-2)). Prolonged irradiation of BiVO(4)/CoPi (ED) resulted in a reduced Co?:?P ratio to 1?:?1.77 without changing the mixed valency of Co(II/III). This finding indicates that incorporation of phosphate into the CoPi was kinetically slower than water oxidation. The primary role of CoPi has been suggested as a hole-conducting electrocatalyst making the photogenerated electrons more mobile and, consequently, increasing conductivity and boosting the PEC water oxidation performance of BiVO(4).     

Efficient and stable photo-oxidation of water by a bismuth vanadate photoanode coupled with an iron oxyhydroxide oxygen evolution catalyst

BiVO(4) films were prepared by a simple electrodeposition and annealing procedure and studied as oxygen evolving photoanodes for application in a water splitting photoelectrochemical cell. The resulting BiVO(4) electrodes maintained considerable photocurrent for photo-oxidation of sulfite, but generated significantly reduced photocurrent for photo-oxidation of water to oxygen, also decaying over time, suggesting that the photoelectrochemical performance of BiVO(4) for water oxidation is mainly limited by its poor catalytic ablity to oxidize water. In order to improve the water oxidation kinetics of the BiVO(4) electrode, a layer of FeOOH was placed on the BiVO(4) surface as an oxygen evolution catalyst using a new photodeposition route. The resulting BiVO(4)/FeOOH photoanode exhibitied significantly improved photocurrent and stability for photo-oxidation of water, which is one of the best among all oxide-based phoatoanode systems reported to date. In particular, the BiVO(4)/FeOOH photoanode showed an outstanding performance in the low bias region (i.e., E < 0.8 V vs RHE), which is critical in determining the overall operating current density when assembling a complete p-n photoelectrochemical diode cell. The photocurrent-to-O(2) conversion efficiency of the BiVO(4)/FeOOH photoanode is ca. 96%, confirming that the photogenerated holes in the BiVO(4)/FeOOH photoanode are indeed excusively used for O(2) evolution.     

Directed synthesis of μ-1,3,5 bridged dicyanamides by thermal decomposition of μ-1,5 bridged precursor compounds

Reaction of transition-metal dicyanamides with pyridazine leads to the formation of the ligand-rich 1 : 2 (1 : 2 = ratio between metal salt and organic co-ligand) compounds [M(dca)(2)(pydz)(2)](n) (dca = dicyanamide, pydz = pyridazine) with M = Mn (1-Mn), Fe (1-Fe), Co (1-Co), Ni (1-Ni). In their crystal structures linear polymeric M-(dca)(2)-M chains are found, in which the M(ii) cations are μ-1,5 bridged by the dca anions. The pydz ligands are terminally N-bonded to the cations, which are octahedrally coordinated by two pydz ligands and four dca anions. On heating these precursor compounds, 1-Mn, 1-Fe and 1-Co transform quantitatively into new ligand-deficient 1 : 1 intermediate compounds of composition [M(dca)(2)(pydz)](n) with M = Mn (2-Mn), Fe (2-Fe) and Co (2-Co). Investigations by IR spectroscopy, and single crystal X-ray structure analysis, show that the intermediates form a more condensed layered structure in which half of the pristine μ-1,5 bridged dca anions become μ-1,3,5 bridging. This structural transformation is accompanied by a pronounced change of their magnetic properties: whereas the ligand-rich 1 : 2 compounds show only Curie-Weiss paramagnetism, the ligand-deficient 1 : 1 intermediates show either antiferro- or ferromagnetic ordering at lower temperatures mediated by the three-atom pathway of the μ-1,3,5 bridging dca anions.     

The Solid-State-Grinding Synthesis of Maganese-Modified Cobalt Oxides and Application in the Low-Temperature CO Preferential Oxidation in H<Subscript>2</Subscript>-Rich Gases

A series of MnOx modified cobalt oxides with different atomic molar ratios of Mn/(Mn?+?Co) were prepared by a soft reactive grinding route and investigated for CO preferential oxidation in H₂. It was found that as-prepared Mn-doped cobalt oxides exhibited superior activity compared to the single constituted oxides, other Mn–Co–O mixed oxides synthesized by solution-based route, and other grinding-derived mixed metal oxides M–Co–O (M?=?Zn, Ni, Cu, Fe). The grinding-derived MnCo10 catalyst with Mn/(Mn?+?Co) molar ration of 10% showed the best CO oxidation activity and higher selectivity at low temperature. The surface richness of Co³⁺ was not found as increasing the Mn molar ratio in the present work. However, the incoporation of MnOx with proper amount into Co₃O₄ could produce high surface area, high structure defects, and rich surface active oxygen species, while the ability to supply the active oxygen species was suggested to play the crucial role in promoting the catalytic performance of Mn–Co–O mixed oxides.     

利用Ni(OH)x助催化剂修饰提高g-C3N4纳米片/WO3纳米棒Z型纳米体系的可见光产氢活性的研究

光催化技术是目前解决能源和环境问题最具前景的手段之一,因此寻找高效光催化剂已成为光催化技术的研究热点.而在众多半导体催化剂中,廉价、环保且性能稳定的g-C3N4光催化剂在太阳光开发利用方面尤其引人关注.然而,由于g-C3N4的比表面小,活性位点少,以及光生电子/空穴对易复合等不足,严重导致其较低的光催化量子效率.因此,构造Z型体系和负载助催化剂等策略被广泛应用于提高g-C3N4光催化效率.在过去几年中,TiO2,Bi2WO6,WO3,Bi2MoO6,Ag3PO4和ZnO已经被成功证实可以与g-C3N4耦合而构造Z型光催化剂体系.其中,WO3/g-C3N4光催化剂体系,具有可见光活性的WO3导带中的光生电子和g-C3N4价带中的光生空穴容易实现Z型复合,从而保留了WO3的强氧化能力和g-C3N4的高还原能力,最终大幅度提高了整个体系的光催化活性.在g-C3N4的各种产氢助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来各种非贵金属助催化剂(包括纳米碳,Ni,NiS,Ni(OH)2,WS2和MoS2等)得到了广泛的关注.我们采取廉价且丰富的Ni(OH)x助催化剂修饰g-C3N4/WO3耦合形成的Z型体系,开发出廉价高效的WO3/g-C3N4/Ni(OH)x三元产氢光催化体系.在该三元体系中,Ni(OH)x和WO3分别用于促进g-C3N4导带上光生电子和价带的光生空穴的分离及利用,从而使得高能的g-C3N4的光生电子在Ni(OH)x富集并应用于光催化产氢,而高能的WO3的光生空穴被应用于氧化牺牲剂三乙醇胺,最终实现了整个体系的高效光催化产氢活性及稳定性.我们通过直接焙烧钨酸铵和硫脲制备出WO3纳米棒/g-C3N4,并采用原位光沉积方法将Ni(OH)x纳米颗粒负载到WO3/g-C3N4上.随后,我们采取X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱分析(XPS)和比表面和孔径分布等表征手段来研究光催化剂的结构与形貌;采取紫外-可见漫反射表征方法来研究其光学性能;采取荧光光谱,阻抗和瞬态光电流曲线等表征手段来测试光催化剂的电荷分离性能;采取极化曲线和电子自旋共振谱等表征手段来证明光催化机理;采取光催化分解水产氢的性能测试来研究光催化剂的光催化活性与稳定性.XRD,HRTEM和XPS表征结果,表明WO3为有缺陷的正交晶系的晶体,直径为20–40纳米棒且均匀嵌入在g-C3N4纳米片上;Ni(OH)x为Ni(OH)2与Ni的混合物,其Ni(OH)2与Ni的摩尔比为97.4 : 2.6,Ni(OH)x粒径为20–50 nm且均匀分散在g-C3N4纳米片上,WO3/g-C3N4/Ni(OH)x催化剂界面之间结合牢固,其中WO3和Ni(OH)x均匀分布在g-C3N4上.紫外-可见漫反射表征结果表明,随着缺陷WO3的负载量增加,复合体系的吸收边与g-C3N4相比产生明显的红移,而加入Ni(OH)x助催化剂使得催化剂体系的颜色由黄变黑,明显地增加了可见光的吸收.荧光光谱,阻抗和瞬态光电流曲线结果表明,WO3和Ni(OH)x的加入能有效地促进光生电子/空穴的分离.极化曲线结果表明,掺入WO3和Ni(OH)x能降低g-C3N4的析氢过电位,从而提高光催化剂表面的产氢动力学.?O2?和?OH 电子自旋共振谱表明成功形成了WO3/g-C3N4 耦合Z 型体系.光催化分解水产氢的性能测试表明,20%WO3/g-C3N4/4.8%Ni(OH)x产氢效率最高(576 μmol/(g?h)),分别是g-C3N4/4.8%Ni(OH)x,20%WO3/g-C3N4和纯g-C3N4的5.7,10.8和230倍.上述结果充分证明,Ni(OH)x助催化剂修饰和g-C3N4/WO3 Z型异质结产生了极好的协同效应,最终实现了三元体系的极高的光催化产氢活性.