Photocatalytic performance of graphitic carbon nitride (g-C3N4): tuning factors, mechanisms, challenges, and opportunities

Abstract

Abstract Graphitic carbon nitride (g-C3N4) has emerged as the most significant metal-free photocatalyst owing to its suitable band gap, chemical stability, and low-cost synthesis. However, its practical photocatalytic performance is limited by rapid charge recombination, low surface area, and insufficient visible-light absorption. This review provides a comprehensive and critical analysis of the key factors governing the photocatalytic activity of g-C3N4 and the strategies employed to tune its performance. Fundamental properties like electronic structure and photocatalytic mechanisms are first discussed to establish a theoretical foundation. Subsequently, various tuning approaches like morphology control, heteroatom doping, heterojunction engineering, defect creation, co-catalyst loading, and synthesis optimization are systematically analyzed with mechanistic insights. A comparative evaluation highlights the advantages and limitations of each strategy. The review further explores major applications in environmental remediation, hydrogen evolution, CO2 reduction, and pollutant degradation. Finally, critical challenges like scalability, stability, and mechanistic ambiguity are addressed followed by future research directions. This work aims to provide a clear roadmap for the rational design of high-performance g-C3N4–based photocatalysts.