Recent advances in g–C3N4–Based composites for photocatalytic hydrogen production

The escalating global energy crisis and environmental degradation underscore the urgent need for sustainable hydrogen production. Photocatalytic water splitting, leveraging solar energy to generate hydrogen, presents a green, low-energy solution. Traditional photocatalysts, such as TiO₂, ZnO, and CdS, are constrained by their limited light absorption, rapid electron-hole recombination, and stability concerns. Graphitic carbon nitride (g-C₃N₄) has emerged as a promising alternative due to its broad light absorption spectrum, cost-effectiveness, and chemical stability. However, pure g-C₃N₄ suffers from low charge separation efficiency and surface activity. To address these limitations, advanced modification strategies, including morphology control, elemental doping, and heterojunction construction, have been developed. These strategies enhance light absorption, optimize band structures, promote carrier separation, and introduce active sites, thereby significantly boosting photocatalytic hydrogen evolution. This review systematically summarizes recent advancements in the synthesis, mechanisms, and performance of g-C₃N₄ composites, highlighting their role in improving hydrogen production efficiency. It critically analyzes the interplay between structural modifications and catalytic activity, addressing challenges in stability, scalability, and cost-effectiveness. Future research directions are proposed, emphasizing scalable synthesis techniques, long-term durability assessments, and integration with industrial applications to fully realize the potential of g–C₃N₄–based systems in sustainable energy.