摘要
光催化分解水被认为是非常有前景的制氢技术之一,该技术不依赖传统化石燃料,且避免了温室气体CO_(2)的排放.提升太阳能光催化分解水效率的一个重要前提是开发高效的窄带隙半导体光催化材料.近年来,多种窄带隙半导体,如掺杂氧化物、氮(氧)化物、硫(氧)化物、卤氧化物和卤氮化物等,被开发并应用于可见光光催化分解水反应体系.其中,均匀氮掺杂氧化物是一类典型的窄带隙半导体,主要包含氮掺杂层状或者隧道状氧化物.前期本课题组开发了一系列均匀氮掺杂氧化物并用于可见光光催化分解水体系.通过将MgTa_(2)O_(6-x)N_(x)和TaON构筑异质结后,最终组装出的Z机制全分解水体系的表观量子效率可达12.3%(420 nm).与异质结相比,氮掺杂氧化物本身仍存在电荷分离较差的问题,如何改善该类材料的电荷分离是当前面临的重要挑战之一.表面修饰被认为是一种可以通过减少表面复合中心从而提升电荷分离效率的策略.例如,通过在TaON和Ta3N5半导体表面分别修饰ZrO_(2)和和MgO可以显著减少材料本身的表面缺陷从而提高光催化分解水性能.考虑到氮掺杂氧化物和氮(氧)化物具有相似的组成和性质,本文以氮掺杂隧道状氧化物MgTa_(2)O_(6-x)N_(x)为模型材料,验证了ZrO_(2)修饰策略也可有效改善均匀氮掺杂氧化物类半导体材料的电荷分离,提升光催化分解水性能.首先,对MgTa2O6进行表面修饰,得到ZrO_(2)/MgTa2O6前驱体,再经过掺氮处理后制得ZrO_(2)/MgTa_(2)O_(6-x)N_(x).结果表明,Zr物种以粒径为20nm左右的ZrO_(2)纳米颗粒形式存在,对MgTa_(2)O_(6-x)N_(x)晶体结构和形貌等几乎无影响.紫外可见漫反射光谱和X射线光电子能谱结果表明,ZrO_(2)修饰能在一定程度上抑制MgTa_(2)O_(6-x)N_(x)材料在氮掺杂过程中低价钽物种的生成.将系列样品分别担载产氢或产氧助催化剂后,ZrO_(2)/MgTa_(2)O_(6-x)N_(x)样品的光催化水
Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen,but currently the poor charge separation severely limits their photocatalytic performances.In this work,a homogeneous nitrogen-doped tunneled oxide of MgTa_(2)O_(6‒x)N_(x) with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO_(2) modification on the charge separation as well as photocatalytic performance.It is interesting to observe that the formation of the reduced tantalum species,regarded as recombination centers,in the MgTa_(2)O_(6‒x)N_(x) sample could be effectively inhibited via the surface passivation with ZrO_(2) nanoparticles,based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted.Together with modification of the deposited Pt cocatalyst,the optimized H2 evolution rate over Pt-ZrO_(2)/MgTa_(2)O_(6‒x)N_(x)(Zr/Ta=0.10)photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa_(2)O_(6‒x)N_(x) sample free of ZrO_(2) modification,whose apparent quantum yield at 420 nm(±15 nm)achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts.The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO_(2) modification,which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species.This work extends the application territory of ZrO_(2) modification to the homogeneous nitrogen-doped oxide photocatalysts,and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.
作者
王宁宁
王硕
李灿
李晨阳
刘春江
陈闪山
章福祥
Ningning Wang;Shuo Wang;Can Li;Chenyang Li;Chunjiang Liu;Shanshan Chen;Fuxiang Zhang(School of Materials Science and Engineering&National Institute for Advanced Materials,Nankai University,Tianjin 300350,China;State Key Laboratory of Catalysis,iChEM,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian National Laboratory for Clean Energy,Dalian 116023,Liaoning,China)
基金
国家自然科学基金(22272082,21925206)
中央高校基本科研业务费,南开大学(63213098)
河北省科学技术厅基金(226Z4307G).
