硫化钴装饰BiVO_(4)光阳极提升其光电化学水分解性能

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

太阳能驱动的光电化学(PEC)水分解可以有效地将太阳能转化为化学能,作为解决环境排放和能源危机最具前景的途径之一,已经引起了科学界的广泛关注.PEC水分解系统由两个半反应组成:在光阳极上的析氧反应(OER)和光阴极上的析氢反应(HER).PEC系统的太阳能转化效率主要由光阳极/电解质界面的OER过程所决定,这是一个非常复杂且涉及质子偶联的多步四电子转移过程.钒酸铋(BiVO_(4))是应用于PEC水分解的典型且具有实际应用前景的光阳极材料之一.然而,由于不良的表面电荷转移、电荷在光阳极/电解质结面处的表面复合以及缓慢的OER动力学等因素,导致BiVO_(4)的PEC性能受到严重限制.本文开发了一种新颖有效的解决方案,以低成本、高电导率和具有快速电荷转移能力的硫化钴装饰来提升BiVO_(4)光阳极的PEC活性,X射线多晶衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等表征,研究结果表明CoS成功装饰于BiVO_(4)表面.采用紫外-可见吸收光谱(UV-VisDRS)研究了BiVO_(4)和复合光阳极CoS/BiVO_(4)的光学性质,结果表明,与纯的BiVO_(4)相比,CoS/BiVO_(4)光阳极在可见光范围内光吸收能力有所增强.将制备的BiVO_(4)和CoS/BiVO_(4)光阳极应用于PEC分解水实验中,结果表明,相对于1.23 V可逆氢电极,在光照下,CoS/BiVO_(4)光阳极的光电流密度显著提升,可高达3.2 m Acm^(-2),是纯BiVO_(4)的2.5倍以上.与纯BiVO_(4)相比,CoS/BiVO_(4)光阳极的起始氧化电位显示出负向偏移0.2 V,表明析氧过电势得到有效减小.入射光子转换效率(IPCE)测试结果表明,CoS/BiVO_(4)光阳极的入射光子转换效率在500 nm之前的可见光范围内得到明显提升,其中,CoS/BiVO_(4)的IPCE值在380 nm处达到最大.此外,由于CoS的装饰作用,CoS/BiVO_(4)光阳极的电荷注入效率和电荷分离效率均得到较大的提升,分别达到75.8%(相较于纯BiVO_(4)光阳极的36.7%)和79.8%(相较于纯BiVO_(4)光阳极的66.8%).电化学阻抗谱(EIS)测试结果表明,通过CoS的装饰,CoS/BiVO_(4)光阳极的界面电荷转移电阻得到有效降低,证明其界面电荷转移动力学得到有效提升.光致发光光谱测试结果表明,CoS的装饰显著提高了BiVO_(4)的光生电子-空穴对的分离效率,进一步证明BiVO_(4)表面的CoS装饰在其PEC分解水中起着非常积极的作用.本文为通过表面修饰设计应用于PEC水分解的有效的光阳极提供了新思路.

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.