硫锌镉纳米孪晶耦合可控纳米金属助催化剂的高效可见光催化制氢体系构建

Semiconductor-metal heterojunction plays a significant role on accelerating photogenerated charge separation and interfacial chemical reaction during photocatalytic water splitting. In previous studies, loading of metal cocatalyst was mostly completed via simple photo- or thermal-deposition method, which lacks effective control over the shape and size of metal particles. As a result, in-depth understanding towards the semiconductor-metal interfacial charge transfer mechanism and control means, as well as the structure-activity relationship is not available. Based on the research we carried out over efficient ordered Cd1-xZnxS twin homojunction photocatalyst (quantum efficiency for hydrogen production: 62%) and controllable synthesis of metal nanoparticles, we will firstly optimize the synthetic conditions to obtain one-dimension long-range ordered homojunction nanotwins, and further use them as seeds to grow metal nanoparticles in aqueous solution. By controlling the reaction kinetics, we will study the nucleation and growth mechanism to realize the targeted deposition of metal cocatalyst on the surface of the twins, giving rise to the formation of ordered twin-metal homojunction-heterojunction coupled photocatalyst. In particular, by successively changing the shape and size of the co-catalyst, we will then emphasize on the understanding of the facet- and size-effect of metal cocatalyst for photocatalytic H2 evolution, and revealing the dynamics of interfacial charge transfer and surface chemical reaction. The project will provide technical and theoretical support for future targeted design of heterojunction photocatalyst and corresponding hydrogen production system with high efficiency but low cost.

半导体-金属异质结对促进光催化分解水制氢过程中光生电荷分离和界面化学反应至关重要。以往的研究，金属的负载多以简单的光沉积或热沉积完成，缺乏对颗粒尺寸和形貌有效控制，也因此对主、助催化剂界面电荷的传输机理、控制手段及构效关系缺乏深入认知。本项目申请人基于在高活性硫锌镉孪晶有序同质结光催化剂（制氢量子效率62%）及金属纳米颗粒可控合成两方面的工作，将首先优化合成条件，获得一维长程有序同质结纳米孪晶，并进一步以此为种子，水相生长金属纳米颗粒，通过动力学控制研究其成核和生长机理，实现助催化剂在孪晶体表面的定向沉积，形成基于一维孪晶的有序同质结-异质结耦合光催化剂。特别是通过对助催化剂纳米颗粒形貌、尺寸的连续调控，展开对其晶粒不同暴露晶面和尺寸对整个光催化制氢过程影响的研究，揭示光生电荷在界面处传输及表面化学反应动力学机理，为进一步定向制备高效低成本异质结光催化剂及其耦合制氢体系提供技术和理论指导。

半导体-金属异质体系的构建对促进光催化分解水制氢过程中光生电荷分离和界面化学反应至关重要。项目负责人在前期工作中提出通过孪晶界面引入新相形成基于相界面的半导体“有序结”的新概念，成功实现了无贵金属负载的纳米同质结高效光催化剂产氢。本项目首先针对同一物质中两种晶相和不同物质所形成的相界面结构的生长机理进行深入研究，开发出基于Cd1-xZnxS孪晶固溶体的一维长程有序光催化剂；建立了短程有序到长程有序相界面的动力学控制理论；结合理论计算研究了长程“有序结”光催化剂的催化性能，揭示了该类“结”结构对光生电荷迁移和分离的内在强化机制。进一步，通过研究微观表面反应的能量传递强化，发展了新型金属基助催化剂耦合强化方法，特别是基于新型“碰撞”机制的可控一维孪晶有序半导体-Ni基助催化剂的复合反应体系，实现了太阳能光催化制氢量子效率的大幅提高，达94％。该研究在863 计划项目“低成本规模化太阳能连续制氢关键技术及其示范”的共同资助下，逐步实现该类催化剂公斤级生产。生产的催化剂被成功用于团队发展的太阳能制氢示范装置上，并实现长周期连续运行，太阳能制氢能量转化效率达到6.6％，为国际同期报道最高值。该研究从能源有序高效转化出发，揭示光生电荷在界面处传输及表面化学反应动力学机理，为进一步定向制备高效低成本光催化剂及其耦合制氢体系提供技术和理论指导。