Role of Oxygen Vacancy in the Photocarrier Dynamics of WO3 Photocatalysts: The Case of Recombination Centers
Role of Oxygen Vacancy in the Photocarrier Dynamics of WO3 Photocatalysts: The Case of Recombination Centers
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DOI：
10.1021/acs.jpcc.2c01662
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发表时间：
2022-06-09
影响因子：
3.7
通讯作者：
Yamakata, Akira
中科院分区：
文献类型：
--
作者：
Kato, Kosaku;Uemura, Yohei;Yamakata, Akira
粉末光催化剂的缺陷决定了其光催化活性。缺陷的加入有时会增强活性，有时会降低活性，但决定这两种情况差异的因素尚未完全阐明。本文利用宽带瞬态吸收光谱研究了WO3粉末中氧空位对光生载流子动力学的影响。结果表明，当氢还原增加氧空位数时，深陷电子的衰减速度加快。这一结果表明，在WO3中的氧空位主要作为复合中心。这与许多其他光催化剂如TiO 2和SrTiO 3形成对比，其中载流子寿命随着氧空位浓度的增加而增加。这些差异可以归因于氧空位之间的距离的差异。当缺陷被分散时，被俘获的电子需要通过在缺陷之间重复跳跃和隧穿而长距离行进以与空穴联合收割机结合，从而导致减速复合。相反，当缺陷连接或靠近在一起时，被捕获的电子可以容易地在缺陷之间迁移，导致增强的复合。因此，控制缺陷之间的距离对于增强光催化活性是重要的。
Defects in powder photocatalysts determine the photocatalytic activity. The addition of defects sometimes enhances the activity, but sometimes decreases it. However, the factors determining the difference between these cases have not been fully elucidated yet. Herein, we investigated the effects of oxygen vacancies on photocarrier dynamics in WO3 powder using broadband transient absorption spectroscopy. It was found that the decay of deeply trapped electrons was accelerated when the number of oxygen vacancies was increased by H-2 reduction. This result suggests that oxygen vacancies in WO3 mainly act as recombination centers. This is in contrast to many other photocatalysts such as TiO2 and SrTiO3, where the carrier lifetime increases with increasing oxygen vacancy concentration. These differences can be attributed to the difference in the distance between oxygen vacancies. When defects are dispersed, trapped electrons need to travel over long distances by repeatedly hopping and tunneling between defects to combine with holes, resulting in decelerated recombination. In contrast, when the defects are connected or located close together, the trapped electrons can readily migrate among defects, leading to enhanced recombination. Control of the distance between defects is thus important for enhancing photocatalytic activity.