La-doped and AgO-loading g-C3N4 heterojunctions for enhanced photocatalytic hydrogen evolution from water splitting

Abstract

Photocatalytic hydrogen evolution through water splitting represents a sustainable approach for green energy generation. Graphitic carbon nitride (g-C₃N₄)-based Z-scheme heterostructures have emerged as promising photocatalysts, but their practical applications are fundamentally limited by the persistent challenge of rapid charge recombination at heterointerfaces. To address this critical issue, we develop a novel Z-scheme photocatalyst AgO/La@g-C₃N₄ (ALCN) through integration of lanthanum-doped g-C₃N₄ nanosheets with AgO nanoparticles. Comprehensive structural analyses, optical characterization, and electrochemical evaluations confirm the successful construction of p-n heterojunctions with optimized band alignment. The engineered ALCN composite exhibits remarkable electron-hole separation efficiency, achieving an exceptional hydrogen production rate of 16.7 mmol g⁻¹ h⁻¹ under solar light irradiation, which represents a 13-fold, 4-fold, and 2-fold enhancement compared to pristine g-C₃N₄, La-doped g-C₃N₄, and the composite of La-doped g-C₃N₄ with Ag₂O counterparts, respectively. Mechanistic studies reveal that La-doping induces intermediate energy states facilitating charge migration, while the AgO/g-C₃N₄ heterojunction establishes directional Z-scheme charge transfer pathways. The optimized photocatalyst maintains 92 % activity after 5 cycles, demonstrating superior stability. This work establishes a new paradigm for designing efficient Z-scheme systems through synergistic metal loading and heterojunction engineering.