Multielectron photocatalysis requires sequential, multiple charge transfer from the light absorber to the catalytic site. As a result, many-body effects induced by charge accumulation play a fundamental role in these reactions, especially when photocatalysts are miniaturized to the nanoscale. Here we study sequential two-electron transfer in a state-of-the-art nano-photocatalyst, CdSe@CdS dot-in-rod (DIR) decorated with Pt tips, using pump-pump-probe transient absorption spectroscopy. Following the first electron transfer (ET) from DIR to the Pt tip, the second ET not only needs to compete with Auger recombination of a positively charged exciton but also experiences a large Coulomb barrier exerted by two holes. As a result, both the ET rate and efficiency decrease by an order of magnitude. Analysis using a dissociation-limited long-range charge transfer model reveals that the Coulomb barrier of the second ET is ~60 meV higher than that of the first one. This study not only uncovers the mechanism and efficiency bottleneck of a real multi-electron photocatalyst but also provides general guidelines to the design of multielectron photocatalytic systems.

中文翻译：

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纳米工程光催化剂中连续两电子转移的库仑势垒

多电子光催化需要从光吸收剂到催化位点的连续多次电荷转移。因此，电荷积累引起的多体效应在这些反应中起着重要作用，尤其是当光催化剂被小型化到纳米级时。在这里，我们使用泵 - 泵 - 探针瞬态吸收光谱研究了最先进的纳米光催化剂 CdSe@CdS 棒中点（DIR）中的连续双电子转移，该催化剂用 Pt 尖端装饰。在从 DIR 到 Pt 尖端的第一次电子转移 (ET) 之后，第二次 ET 不仅需要与带正电的激子的俄歇复合竞争，而且还要经历由两个空穴施加的大库仑势垒。结果，ET 速率和效率都下降了一个数量级。使用离解受限长程电荷转移模型的分析表明，第二个 ET 的库仑势垒比第一个高约 60 meV。这项研究不仅揭示了真正的多电子光催化剂的机理和效率瓶颈，而且为多电子光催化系统的设计提供了一般指导。