摘要
在光电化学(PEC)中,利用半导体纳米材料分解水产生氧气和氢气成为解决能源和环境危机的有效途径,而设计具有较高的光子捕获效率和电荷分离率的低成本光电极是研究的重点.近年来,已有许多半导体材料(例如ZnO,Fe2O3,WO3,Cu2O,CuInS2等)被用做光电极参与光电催化分解水.其中,TiO2作为一种n型半导体,由于其具有适当的导带(CB)和价带(VB)位置、良好的耐光腐蚀性、无毒性和出色的稳定性而引起人们的关注.然而,光响应范围窄,光生载流子复合率高等问题限制了TiO2光电极在PEC水分解中的应用.因此,选用合适的窄禁带半导体和助催化剂进行复合修饰能够有效地扩大光响应范围,促进载流子的分离和转移,从而提升电极的光电催化性能.本文利用具有表面等离子体共振(SPR)效应的Al对TiO2/Cu2O核/壳异质结进行改性,制备了TiO2/Cu2O/Al/Al2O3光电阳极.SEM和TEM等结果显示已成功合成核/壳异质结.UV-vis吸收光谱和UPS测试计算表明,Cu2O不仅可以显著扩展电极的吸光范围,且计算所得TiO2和Cu2O导价带位置验证了p-n异质结的合成.结合光电流、EIS等测试,证明了异质结能够有效地促进光生载流子的分离和转移.同时,在光照激发下,UV-vis吸收光谱在550 nm出现明显的特征峰,表明Al的SPR效应被成功激发.Al纳米颗粒的SPR效应不仅可以产生热电子,并能够增强与异质结界面处的电场.之后,通过Mott-Schottk测试和Bode图,较为直观地说明了异质结和SPR效应的协同作用能够增加载流子的浓度,抑制电子空穴的复合,使所制备的TiO2/Cu2O/Al/Al2O3光电阳极表现出良好的光电性能,其光电流达到了4.52 mA/cm^2(1.23 V vs.RHE),是TiO2/Cu2O异质结的1.84倍.相比于同样具有SPR效应的Au,Ag等贵金属而言,Al不仅价格低廉,而且在空气中自发形成的超薄Al2O3薄膜能够有效地抑制Al的进一步氧化,并作为保护层能够显著提高电极的稳定性.在对样品稳定性的测试中,由于Al2O3保护层的存在,电极的稳定性提高了53%.本文对样品的实验测试和原理分析表明了异质结和非贵金属Al的SPR效应的协同作用显著提高了光电极的光电性能,为设计具有良好性能和高实用性的电极提供了新思路.
Designing low-cost and high-performance photoelectrodes with improved light harvesting and charge separation rates is significant in photoelectrochemical water splitting.Here,a novel TiO2/Cu2O/Al/Al2O3 photoelectrode is manufactured by depositing plasmonic nanoparticles of the non-noble metal Al on the surface of a TiO2/Cu2O core/shell heterojunction for the first time.The Al nanoparticles,which exhibit a surface plasmon resonance(SPR)effect and are substantially less expensive than noble metals such as Au and Ag,generate hot electron-hole pairs and amplify the electromagnetic field at the interface under illumination.The as-prepared TiO2/Cu2O/Al/Al2O3 photoelectrodes have an extended absorption range and enhanced carrier separation and transfer.Their photocurrent density of 4.52 mA·cm^-2 at 1.23 V vs.RHE represents an 1.84-fold improvement over that of TiO2/Cu2O.Specifically,the ultrathin Al2O3 passivation layer spontaneously generated on the surface of Al in air could act as a protective layer to significantly increase its stability.In this work,the synergistic effect of the heterojunctions and the SPR effect of the non-noble metal Al significantly improve the photoelectrode performance,providing a novel concept for the design of electrodes with good properties and high practicability.
作者
张劭策
刘志锋
闫卫国
郭振刚
阮梦楠
Shaoce Zhang;Zhifeng Liu;Weiguo Yan;Zhengang Guo;Mengnan Ruan(School of Materials Science and Engineering,Tianjin Chengjian University,Tianjin 300384,China;Tianjin Key Laboratory of Building Green Functional Materials,Tianjin Chengjian University,Tianjin 300384,China)
基金
天津市杰出青年基金(17JCJQJC44800)
天津市重点研发计划项目(19YFSLQY00020).
