有机光催化剂用于太阳能水分解：分子水平和聚集体水平改性

利用太阳能光解水产氢是实现氢能开发最绿色且可持续的理想技术。为了提高太阳能的转换效率，设计和发展高效、稳定、宽/全光谱响应光催化产氢体系成为关键研究课题。相比于无机半导体，有机半导体具有丰富的π电子和结构可修饰性，使其光学吸收和能带结构易剪裁，光催化路径多样。但低的介电常数造成其载流子迁移率低及迁移距离短。通过有目的地改变有机分子结构，可以轻松地设计和调控有机半导体的能带位置、增加摩尔吸光系数，改善材料对于整个太阳光谱中可见光或红外光的利用；通过功能分子微纳组装或集成，可进一步获得不同组分、维度(0维、1维、2维、3维)、尺寸、晶体学取向的有机光催化剂。有机微纳/复合结构的优异的比表面积、分子排布结构或能级排列结构可进一步提高太阳能的利用率和光生电荷的传输/分离效率，从而提高整体光电转换效率和产氢效率。然而，由于复杂的反应过程和设计困难，整个有机半导体的光催化物理化学过程仍不清楚。在这里，光催化的基本原理从光捕获、光激发电荷分离、表面反应的角度进行了讨论。随后详细总结了有机半导体纳米结构的制备方法包括超分子自组装、再沉淀法、气相沉积法以及其他方法。描述了典型的有机半导体材料，包括苝二酰...

Organic Photocatalysts for Solar Water Splitting: Molecular- and Aggregate-Level Modifications

Photocatalytic water splitting is a green technology for sustainable hydrogen evolution. To improve photon-to-electron conversion efficiency, the design and development of efficient, stable, and full-spectrum responsive photocatalysts has attracted increasing attention. Many different classes of materials can be used to harness solar photons for photocatalysis, each having their advantages and drawbacks. Compared to inorganic semiconductors, organic semiconductors are rich in π electrons and can be readily modified, allowing for facile control of the optic (absorption region and intensity) and electronic (energy structure) properties, as well as mechanistic pathways. However, photogenerated charge carriers cannot be effectively employed owing to subpar charge carrier transport properties, which arise from the low concentration and low mobility of free charge carriers in organic semiconductors. Appropriate changes in the molecular structure of the organic semiconductors can allow for sunlight utilization across the full visible region and even the infrared region. By controlling the nature of stacking, organic photocatalysts with different compositions, dimension (0, 1, 2, 3), size, and crystallographic orientation can be harnessed to increase sunlight utilization and charge separation efficiencies. By optimizing these properties, the overall photoelectric conversion efficiency and hydrogen production efficiency can be improved. However, the mechanisms of redox reactions in organic semiconductor photocatalytic systems remain unclear owing to the complex nature of the processes and difficulties in study design. Herein, the physical and chemical processes of organic semiconductors are discussed from the perspective of light harvesting, photoexcited charge separation, and surface reactions. The preparation methods of organic semiconductor nanostructures are summarized and the progressive development of organic nanostructures for photocatalytic hydrogen evolution is systematically reviewed. Typical organic semiconductor materials, including perylene diimide, porphyrin, phthalocyanine, fullerenes, graphitic carbon nitride (g-C₃N₄), and other conjugated polymers, are highlighted. Moreover, modification strategies for optimizing optical and electrical properties at the molecular or aggregate level are discussed. Element doping or substitution and group functionalization at the molecular level as well as control over morphologies, components, and dimensions at the aggregate level are reviewed to clarify structure/property relationships and further guide photocatalyst design. All the strategies discussed herein focus on enhancing hole and electron separation while suppressing their recombination, thereby improving the photocatalytic performance in evolution hydrogen. Finally, the key challenges and prospects of organic nanomaterials for photocatalytic evolution hydrogen are presented. We particularly focus on the construction of a system to evaluate the reasonable loading of co-catalysts, photocatalyst morphology regulation, and combined in situ characterization and density functional theory calculations in the context of photocatalytic hydrogen production.