基于g-C3N4量子点的高效宽光谱响应多级结构复合材料的构建及其光催化性能研究

Photocatalysis is one of the ideal strategies to solve the global environmental pollution and energy crisis. However, its practical application is largely restricted by the narrow photoresponse range and/or low quantum efficiency of photocatalysts. Therefore, extending the absorption range and promoting the efficient separation of photo-generated charge are two key issues to be solved for designing highly efficient photocatalysts. This proposed project is seeking to develop highly efficient, ultraviolet (UV)-near-infrared (NIR) activated g-C3N4 quantum dots/TiO2/conducting polymer hierarchical composite by controlling the functional groups of g-C3N4 quantum dots, which are covalently bonded to TiO2 and conducting polymer. The covalent bonds at the heterogeneous interface as the charge transport channel and high carrier mobility of conducting polymer in the composite synergistically facilitate the separation and transfer of photo-generated charge, leading to the increased quantum efficiency. Moreover, the utilization of solar energy over a broad spectrum range can be realized by enhancing the upconversion emission of g-C3N4 quantum dots and modulating the light scattering characteristic of hierarchical structure. The structure and the associated photocatalytic performance of the composite will be systematically investigated by combining experiment and theoretical computation, so as to clarify the mechanism of facilitating photo-generated charge separation and transfer, and to reveal its physical mechanism of wide spectral response and high quantum efficiency, and to optimally design g-C3N4/TiO2/conducting polymer hierarchical photocatalysts with high stability, high activity and UV-NIR photoresponse. The results of this proposed research will provide experimental and theoretical basis for the design of highly efficient and wide spectrum responsive composite photocatalysts.

光催化技术是解决环境污染和能源危机的理想途径之一，目前制约其应用的主要因素是光催化材料的光响应范围窄和量子效率低。因此，拓展光吸收范围和促进光生电荷的有效分离是设计高效光催化材料需要解决的关键问题。本项目拟通过调控g-C3N4量子点官能团，共价偶联TiO2和导电聚合物构建高效、紫外-近红外光响应的多级结构复合光催化材料。利用其异质界面共价键为电荷传输通道和导电聚合物的高电荷迁移率协同促进光生载流子分离和迁移，提高量子效率；通过调控g-C3N4量子点上转换发光光谱、以及多级结构的光散射特性实现对太阳能的宽光谱高效利用。实验结合理论计算探究这类复合材料的结构和光催化性能，阐明促进光生电荷分离与迁移的机理，揭示其宽光谱响应和高量子效率的物理机制，获得稳定、高活性、紫外-近红外光响应的g-C3N4/TiO2/导电聚合物光催化材料。该项目可为高效宽光谱响应复合光催化材料的构建提供实验依据和理论基础。

太阳能光催化分解水制氢是解决能源危机和环境污染问题的理想途径，其核心是宽光谱响应和高量子效率光催化材料的研发。本课题采用多种策略，如构建type-II、Z型、type-II/type-II和高通量单光子激发途径等不同类型的g-C3N4（量子点）复合材料，利用碳、硫和磷等掺杂以及官能团和形貌控制等精确调控材料的拓扑结构和电子结构，以增强体系的催化性能；实验结合第一性原理计算系统深入地研究了工艺参数对各组分和形貌、结构、界面相互作用和界面电荷转移等对Ti-N等共价偶联g-C3N4（量子点）复合材料光电性能和光催化性能的影响，构筑了高效宽光谱响应的g-C3N4（量子点）基复合光催化材料; 制备了粒径尺寸约为5 nm的g-C3N4量子点（CNQDs），其中非晶态B-CNQDs光致发光蓝光量子产率高达87.4%，对Fe2+和Cd2+在ppb范围内具有高度的选择性和灵敏度, 在荧光成像和重金属检测领域具有重大的应用前景; 获得的g-C3N4（量子点）复合材料不仅吸收光谱响应被拓宽到全可见光甚至近红外范围，使更多的载流子在宽光谱下被激发，且Ti-N等共价偶联加速了载流子的定向迁移，光催化产氢和降解有机污染物性能显著增强。如优化后的CDs/PCN NVs异质结催化产氢性能高达14022 μmol h-1 g-1，远高于目前报道的绝大多数g-C3N4基催化剂。这一成果不仅获得了高效宽光谱响应的g-C3N4（量子点）基复合光催化材料，而且丰富了对光催化材料空间维度与形貌和催化性能之间关系的理解，揭示了宽光谱响应和高量子效率的物理机制，为研发新颖高效宽光谱响应复合光催化材料提供了实验依据和理论基础。