石墨相氮化碳光解水产氧半反应机制的理论研究

Using polymeric semiconductor graphitic carbon nitride (g-C3N4) as a new type of photocatalyst to achieve metal-free hydrogen generation from water splitting with visible light has opened a new door for photocatalysis. However, the rate of water oxidation half-reaction is low, which is considered to be the rate-limiting step in photocatalytic water splitting by the carbon nitride catalyst. Because the current experimental studies cannot provide enough information on the reaction mechanism over this material, which makes it difficult to understand the experimental resutls and hinders further development of the photocatalysts. In this project, in order to investigate the mechanism of oxygen evolution reaction on carbon nitride surface, first principles method will be used to systematicly study the geometries and electronic structures of active centers, the adsorption behavior of reaction intermediates and reaction pathways, the generation of overpotential and its adjustment, and the effect of doping. This research will help to further understand the photocatalytic water splitting on carbon nitride and eventually design and synthesize more efficient polymeric semiconductor based photocatalysts, which is of therotaical and pratical importance to construct a photocatalytic system for solar energy conversion with high efficiency.

利用高分子半导体石墨相氮化碳（g-C3N4）作为新型光催化剂，实现无金属组分光催化体系的可见光分解水制氢，为光催化研究领域开拓了新的方向。但是，氮化碳光解水产氧半反应速率很低，被认为是制约实现太阳能高效分解水的关键动力学步骤。由于当前实验研究尚缺乏对这类新材料微观反应机制的认识，难以解释实验结果和开展光催化剂的进一步改性工作。本项目拟从第一性原理出发，通过对氮化碳光解水产氧半反应活性中心的空间结构与电子构型、反应中间体的吸附行为和反应途径、催化剂表面过电势的产生和调控规律、掺杂作用本质等的系统理论研究，阐明产氧半反应的微观机制，揭示制约氮化碳高效光催化分解水制氧的关键因素，构建基于分子水平的氮化碳光解水反应机理模型。该研究对氮化碳光解水产氧半反应机制的深刻理解、指导新型高分子半导体光催化剂的设计和合成、构筑具有高量子效率和太阳能利用率的高分子半导体基光催化体系都具有重要的理论和现实意义。

利用高分子半导体石墨相氮化碳（g-C3N4）作为新型光催化剂，实现无金属组分光催化体系的可见光分解水制氢，为光催化研究领域开拓了新的方向。但是，氮化碳光解水产氧半反应速率很低，被认为是制约实现太阳能高效分解水的关键动力学步骤。由于当前实验研究尚缺乏对这类新材料微观反应机制的认识，难以解释实验结果和开展光催化剂的进一步改性工作。本项目从第一性原理出发，通过对氮化碳光解水产氧半反应反应中间体的吸附行为和反应途径、导致高过电势的重要因素、掺杂作用本质等的系统理论研究，阐明了该半反应的微观机制，揭示制约氮化碳高效光催化分解水制氧的关键因素。我们通过计算发现OH中间体的吸附能的大小在很大程度上影响了过电势的大小，因此在掺杂元素的选择上要着重考虑掺杂后氮化碳对OH的吸附能力。该研究成果对氮化碳光解水产氧半反应机制的深刻理解、指导新型高分子半导体光催化剂的设计和合成、构筑具有高量子效率和太阳能利用率的高分子半导体基光催化体系都具有重要的理论和现实意义。