Rare Earth Doping‐Regulated G‐C ₃ N ₄ ‐Based Photocatalysts: Heterojunction Construction, Mechanisms, and Synergistic Applications in Energy and Environment

ABSTRACT Graphitic carbon nitride (g‐C 3 N 4 ) is a promising metal‐free semiconductor photocatalyst for energy conversion and environmental remediation, due to its suitable band gap, excellent stability and low‐cost synthesis. However, its inherent limitations (rapid photogenerated electron–hole recombination, small specific surface area, narrow visible‐light absorption) severely restrict practical applications. Rare earth elements, with unique 4f electronic configurations, abundant energy level transitions and strong electron transfer capabilities, are ideal modifiers for g‐C 3 N 4 . This review systematically summarizes the research progress of rare earth‐doped g‐C 3 N 4 ‐based photocatalysts, focusing on fundamental theories, heterojunction modification strategies and typical applications. The combination of rare earth doping and Z‐scheme, S‐scheme or 2D/2D heterojunctions synergistically enhances charge separation, visible‐light utilization and redox capability, endowing the catalysts with remarkable performance in water splitting, CO 2 reduction and pollutant degradation. Current challenges and future directions are also prospected, including revealing structure‐activity relationships via in situ characterization and DFT calculations, constructing integrated modification systems and advancing engineering applications. This review offers valuable insights for designing high‐performance rare earth‐doped g‐C 3 N 4 ‐based photocatalysts, facilitating sustainable energy production and environmental governance.