二维纳米结调控光催化剂光生电荷分离、传输及光催化制氢性能研究

The separation efficiency of photogenerated charge carrier is an important factor in determining the photocatalytic performance of photocatalysts, and it has been to a great challenge to improve the carrier separation efficiency in the field of photocatalytic hydrogen generation. Based on our previous studies, binary (light-harvesting semiconductor/cocatalyst) and ternary (light-harvesting semiconductor/charge transfer medium/cocatalyst) two-dimensional nanojunction photocatalysts would be constructed. Such an excellent structure provides intimate and large contact area for fast interfacial charge separation, which could play a key factor in determining the photocatalytic performance and light-to-H2 conversion efficiency of photocatalytic system. The aim of this project is to solve the following problems: studying the effect of two-dimensional nanjunction on both lifetime of photogenerated charge carrier and the carrier separation efficiency by transient absorption spectra, time-resolved luminescence spectra and First-principles calculation; revealing the mechanism of two-dimensional nanjunction on the ehhanced photogenerated charge carrier separation efficiency; improving both the carrier separation efficiency and photocatalytic activities of photocatalysts, these results would provide important reference values to construct highly-efficient, stable, environmentally-friendly and low-cost solar hydrogen generation system.

光催化剂光生电荷分离效率是影响光催化剂性能的一个重要因素，提高光催化剂光生电荷分离效率是当前该研究领域的一个重要挑战。本项目在前期工作的基础上，构建基于二维纳米材料的二元(半导体主催化剂/助催化剂)和三元(半导体主催化剂/电荷传输介质/助催化剂)二维纳米结光催化剂。通过在光催化剂材料之间构建具有较大接触界面的二维纳米结，为光催化剂光生电荷传输提供有效的传输通道，增强光催化剂的光生电荷传输，提高光催化剂的性能和光转换效率。本项目旨在通过瞬态吸收光谱、时间分辨发光光谱和第一性原理等测试和理论计算方法研究二维纳米结对光催化剂光生电荷寿命和载流子分离效率的影响规律，揭示二维纳米结增强光催化剂光生电荷传输作用机制，实现对光催化剂光生电荷分离的主动调控，提高光催化剂的光生电荷分离效率和光催化性能，为构建高效、稳定、环境友好、低成本的太阳能制氢体系提供重要的借鉴和参考价值。

界面状况是影响异质结光催化剂制氢性能的主要因素之一，本项目通过调控光催化剂界面，制备二维纳米结异质结光催化剂，实现增强异质结光催化剂的制氢性能。研究发现：（1）通过构建2D-2D CdS/MoS2, g-C3N4/石墨烯/MoS2等二维纳米结光催化剂，阐明了二维纳米结光催化剂存在较大的接触界面，为载流子传输提供了有效传输通道，减低了界面载流子传输能垒，丰富了反应活性位点，有效提高了光生载流子分离效率并增强了光催化制氢性能。（2）探讨二维光催化材料生长机理，实现对光催化材料结构的主动调控。研制出可见光响应、绿色、低成本和稳定的二维纳米结光催化剂，所研制的二维纳米结光催化剂最高的制氢效率达到了26.32 mmol•h-1•g-1，在450nm处表观量子效率达到了46.65%。（3）深入研究了二维纳米结光催化剂界面微结构对光催化性能的影响规律，发现在光催化剂界面构建界面化学键，为光催化剂载流子传输提供了有效的通道，降低了界面电荷传输的能垒，这对提高光催化剂光生载流子分离效率和增强光催化制氢性能起着至关重要的作用。（4）拓展了二维纳米结光催化剂的应用范围，开发的MoS2/TiO2二维纳米结光催化剂实现光驱动木质纤维素产氢,在α-纤维素和杨木屑水溶液中的催化产氢速率分别为201 μmol•h-1•g-1和21.4 μmol•h-1•g-1，在380 nm处的表观量子产率达到1.45%。以上围绕二维纳米结光催化剂的研究取得的重要成果将为开发高效、低成本的太阳能制氢技术提供理论指导。