Hydrogen evolution over pristine semiconductors is desirable but seldom realized in powdered photocatalysis. It requires the catalyst surface simultaneously possessing efficient electron transfer and rapid H₂ production properties. The current semiconductor photocatalysts have to depend on additional cocatalysts to achieve the H₂ evolution process. Herein, theoretical and experimental results demonstrate that metastable sulfur vacancy could significantly enhance the intrinsic H₂ evolution behavior of semiconductors. The hydrogen adsorption free energy (ΔG_H) of CdS could be optimized to ΔG_H = 0.01 eV, much lower than that over thermodynamically stable vacancies (ΔG_H = 0.31 eV). The experiment is conducted based on kinds of supported CdS nanoparticles prepared with the anion-exchange method. A series of in situ characterizations disclose that a metastable sulfur vacancy forms under photoexcitation and is stable during the reaction. These metastable sulfur vacancies cause the formation of intermediate states between the valence band and the conduction band that increase transportation and utilization of photogenerated electrons. The conceptual finding of the critical role of the metastable vacancy in enhancing H₂ evolution would bring new thinking on the design of semiconductor photocatalysts to be less dependent on cocatalysts.

中文翻译：

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光致亚稳态硫空位的产生增强了半导体的本征析氢行为

在原始半导体上析氢是可取的，但在粉末光催化中很少实现。它要求催化剂表面同时具有有效的电子转移和快速的 H ₂生产特性。目前的半导体光催化剂必须依赖额外的助催化剂来实现 H ₂析出过程。在此，理论和实验结果表明，亚稳态硫空位可以显着增强半导体的本征 H ₂析出行为。CdS的氢吸附自由能 (Δ G _H ) 可以优化为 Δ G _H  = 0.01 eV，远低于热力学稳定空位 (Δ G_H  = 0.31 eV）。实验以阴离子交换法制备的负载型CdS纳米粒子为基础进行。一系列原位表征揭示了在光激发下形成亚稳态硫空位并且在反应过程中是稳定的。这些亚稳态硫空位导致价带和导带之间形成中间态，从而增加光生电子的传输和利用。亚稳态空位在促进 H ₂演化中的关键作用的概念性发现将为半导体光催化剂的设计带来新的思考，以减少对助催化剂的依赖。