Synergistic mechanisms of boron-doped heptazine/triazine homojunction in polymeric carbon nitride for efficient photocatalytic H2O2 evolution

Abstract

Investigating the underlying mechanisms and catalytic performance of various heterostructure configurations in photocatalytic processes has become a central focus in the field of photocatalysis. Herein, a boron-doped heptazine/triazine (H/T) homojunction was successfully synthesized within a crystalline carbon nitride (MCN-xB–LiK) framework and applied to the selective two-electron oxygen reduction reaction (2e⁻-ORR), enabling efficient hydrogen peroxide (H₂O₂) production. Boron oxide served as a structural modulator, fostering the development of a molecular-scale H/T heterostructure enriched in triazine rings. The integration of boron atoms and optimization of the H/T heterojunction ratio in MCN-xB–LiK improved O₂ adsorption and activation, which established a donor–acceptor (D–A) architecture and reduced the interlayer spacing, thereby facilitating efficient charge carrier separation and transfer. Therefore, the two-step single-electron ORR pathway was ultimately promoted for H₂O₂ generation. As a result, MCN-200B–LiK achieved an H₂O₂ production rate of 2423 µmol L⁻¹ h⁻¹ under visible light, with an apparent quantum yield (AQY) of 14.4% at 450 nm, outperforming many reported benchmarks. Our findings demonstrate a viable strategy for tuning the H/T homojunction to boost the photocatalytic efficacy of polymeric carbon nitride (PCN)-based materials.