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光电催化分解水系统能直接将收集的电子与空穴用于分解水,将太阳能转化成了具有高能量密度的氢气,是一种集太阳能转化和储存于一体的高效绿色能源系统。光阴极和光阳极串联要求其在工作状态下两电极通过的总电流必须一致,低效率的一端将会限制整个体系的反应速度,因此对于光阳极材料的系统研究具有十分重要的意义。理论预测表明,基于部分可见光响应的半导体光阳极能带间隙计算得到的极限太阳能制氢转化效率达到了15%。但实际上由于光催化的整个过程是一个多步反应,各个步骤上发生的光生载流子的复合和损失导致了目前合成的相关电极材料的转换效率远低于理论水平。一般可以认为光催化过程包括五个步骤:光电极材料中电子的光致激发而产生电子-空穴对、电子和空穴由于能带弯曲的反向分离和传递、电子(或空穴)通过半导体-电解液界面的注入水中析氢(或析氧)、载流子的复合以及反应物和产物的传质过程。由于这些过程的进行效率与电极材料的本质特性和性能密切相关,为了评估材料性能而引入的一些效率指标往往和这几个步骤相对应。本文首先简要介绍了评价光阳极的一些效率计算以及它们与上述各个步骤的内在联系。最后,在前人和最近的研究基础上总结了几种对光阳极材料的主要提升策略,包括形貌控制、元素掺杂、异(同)质结和表面修饰等改性方法,对这些改性方法和各步骤效率之间的联系作了简单的介绍。
The photoelectrocatalytic decomposition water system can directly collect the electrons and holes used to decompose water and convert the solar energy into hydrogen with high energy density. It is an efficient green energy system integrating solar energy conversion and storage. The photocathode and photoanode series are required to have the total current passing through the two electrodes in the working state must be consistent, and the low efficiency end will limit the reaction speed of the whole system. Therefore, it is of great significance for the system research of photoanode material. The theoretical predictions show that the solar photovoltaic conversion efficiency of the solar photovoltaic based on partial visible light response calculated by bandgaps reaches 15%. However, in fact, the photocatalytic whole process is a multi-step reaction, and the recombination and loss of photo-generated carriers at various steps lead to the conversion efficiency of the currently synthesized electrode materials far below the theoretical level. Generally, it can be considered that the photocatalysis process includes five steps: photo-induced excitation of electrons in the photoelectrode material to generate electron-hole pairs, the electrons and holes being separated and transmitted by reverse bending of the bandgap, electrons (or holes) Hydrogen (or oxygen evolution) in semiconductor-electrolyte interface injection, recombination of carriers and mass transfer of reactants and products. Because the efficiency of these processes is closely related to the intrinsic properties and performance of the electrode materials, some of the efficiency measures introduced to evaluate material properties often correspond to these steps. This paper starts with a brief introduction of some efficiency calculations for the evaluation of photoanodes and their intrinsic relationships with each of the above steps. Finally, based on the previous studies and recent studies, several main improvement strategies for photoanode materials are summarized, including modification of morphology control, elemental doping, heterogeneous junction and surface modification, The link between the sexual method and the efficiency of each step is briefly described.