Multi-scale structural design and performance optimization of g-C3N4 for efficient photocatalytic water splitting: A review

Photocatalytic water splitting, which harnesses solar energy to produce hydrogen, presents a viable approach to addressing contemporary energy and environmental challenges by transforming intermittent sunlight into storable chemical energy. As an organic semiconductor, polymerized carbon nitride has the advantages of high physical and chemical stability, visible light response, abundant synthetic raw materials, and easy adjustment of energy band structure. It has great potential in the field of photocatalytic decomposition of water to produce hydrogen. However, the spectral response range of polymerized carbon nitride is limited and the photogenerated carrier recombination effect is significant. These problems seriously reduce the efficiency of solar-to-hydrogen (STH) conversion. Recent research is mainly centered on broadening the spectral response of materials and enhancing carrier separation/migration efficiency through multi-scale structural design and regulation (such as defect engineering, crystal phase control, and modulation dipole field, etc.). This review systematically expounds the advanced strategies for the design and regulation of g-C 3 N 4 multi-scale structure, such as nano-structure design, defect engineering, D–A structure construction and crystal phase structure design. The synergistic effect of these strategies in improving charge separation efficiency and surface redox kinetics was discussed in depth, with particular emphasis on the structure-activity relationship revealed by in-situ characterization and theoretical calculations. In addition, this paper further elaborates on the challenges encountered and prospective research orientations in developing high-performance g-C 3 N 4 photocatalytic materials. This review seeks to supply a general overarching framework for understanding the molecular structure-performance correlation of g-C 3 N 4 and inspire innovative solutions in the field of solar-driven hydrogen production.