Photogenerated Charge Carriers Dynamics on La- and/or Cr-Doped SrTiO3 Nanoparticles Studied by Transient Absorption Spectroscopy
Photogenerated Charge Carriers Dynamics on La- and/or Cr-Doped SrTiO3 Nanoparticles Studied by Transient Absorption Spectroscopy
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DOI：
10.1021/acs.jpcc.9b09324
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发表时间：
2020-01-16
影响因子：
3.7
通讯作者：
Ye, Jinhua
中科院分区：
文献类型：
--
作者：
Ichihara, Fumihiko;Sieland, Fabian;Ye, Jinhua
将元素掺杂到半导体光催化剂中以缩小带隙，从而将光吸收扩展到可见光区域，是水分解（或人工光合作用）应用的常规且广泛采用的策略。然而，一个很少得到解决的关键问题是，尽管可见光区域的活性增加，但紫外光下的光催化活性却急剧下降，导致全太阳光谱下的总性能下降。为了阐明常见现象的起源，本文选择 La,Cr 共掺杂 SrTiO3 作为概念验证模型，通过瞬态吸收光谱探讨掺杂剂对光生载流子行为的影响。通过观察激子发现，在紫外照射下，Cr杂质带的激发限制了SrTiO3价带的激发，导致掺杂材料的光催化活性急剧下降。然而，广泛提出的掺杂位点复合并不是导致紫外光照射性能下降的主要因素，特别是在反应气体（甲醇蒸气）存在的情况下。
Elemental doping into semiconductor-based photocatalysts to narrow the bandgap, thus extending the light absorption to visible light region, is a conventional and widely adopted strategy for water splitting (or artificial photosynthesis) application. However, one critical problem but rarely addressed, is the drastically decreased photocatalytic activity under UV light despite of the increased activity in visible light region, resulting in a decreased total performance under full solar spectrum. In order to elucidate the origin of the commonly observed phenomena, herein we choose La,Cr-codoped SrTiO3 as a proof-of-concept model to probe the effect of dopants on the behavior of photogenerated charge carriers by transient absorption spectroscopy. By observing the excitons, it is found that under UV irradiation, the excitation occurring from the Cr impurity bands limits the excitation of SrTiO3 from valence band, causing the drastic decrease of the photocatalytic activity over doped material. The widely proposed recombination at dopant sites, however, is not dominant for declining the UV light-irradiated performance, especially in the presence of reactant gas (methanol vapor).