Crucial Effect of Ti-H Species Generated in the Visible-Light-Driven Transformations: Slowed-Down Proton-Coupled Electron Transfer
Crucial Effect of Ti-H Species Generated in the Visible-Light-Driven Transformations: Slowed-Down Proton-Coupled Electron Transfer
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DOI：
10.1021/acs.jpclett.0c01196
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发表时间：
2020-05-21
影响因子：
5.7
通讯作者：
Zhao, Jincai
中科院分区：
文献类型：
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作者：
Lin, Yuhan;Yan, Yan;Zhao, Jincai
尽管已经假设质子耦合电子转移(PCET)在基于二氧化钛的太阳能应用中的功率转换效率(PCE)中起关键作用，但可见光(VIS)驱动的PCET反应的内在本质与有限的PCE增益之间的具体关系尚未被很好地揭示。本文详细研究了染料敏化紫外光与TiO2光催化剂上不同醇类与自由基((Bu3ArO中心点)-Bu-t/TEMPO)的反应动力学。我们发现，在相同的光强下，可见光驱动的反应速度比紫外光驱动的反应速度慢得多。在醇预还原的离线暗反应条件下，也观察到了类似的现象。稳定的“Ti-H”中间体的快速形成和不易断裂是PCET减速效应的原因。这一发现揭示了可见光驱动的能量转换应用中的内在瓶颈。
Despite the fact that proton-coupled electron transfer (PCET) has been hypothesized to play a pivotal role in the power conversion efficiency (PCE) of TiO2-based solar-energy applications, the specific relationship between the intrinsic nature of visible-light (Vis)-driven PCET reactions and limited PCE gains has not yet been well revealed. Here we studied the detailed kinetics of reactions between various alcohols and radicals ((Bu3ArO center dot)-Bu-t/TEMPO) on a TiO2 photocatalyst under dye-sensitization Vis irradiation versus direct ultraviolet (UV) irradiation. We found that the rates of Vis-driven reactions were much slower than those of UV-driven reactions under identical light intensity. A similar phenomenon was observed under the off-line dark-reaction conditions in which TiO2 was prereduced by alcohols. The rapid formation and difficult breakage of the stable "Ti-H" intermediate were proposed to account for the slowed-down PCET effect. This finding revealed an inherent bottleneck in Vis-driven energy conversion applications.