Directional electron delivery and enhanced reactants activation enable efficient photocatalytic air purification on amorphous carbon nitride co-functionalized with O/La

Graphitic carbon nitride (g-C3N4) is an intriguing and rising visible light photocatalyst. However, g-C3N4 still suffers from random charge carriers transfer in planes and low efficiency in reactants activation, which leads to unsatisfactory photocatalytic efficiency. Herein, these formidable challenges are addressed via a new strategy of O/La co-functionalization in amorphous carbon nitride (C N-O La), leading to the formation of electronic channels for directional electron delivery in the interlayers, the generation of localized electrons for enhanced reactants activation and thus highly boosted photocatalytic performance for NO removal. With a closely combined experimental and theoretical approach, we have revealed that the breakage of in-plane hydrogen bonds between strands of polymeric melon units with CO32− could promote the amorphization of g-C3N4 and increase the visible light absorption ability. A directional electron delivery pathway (L2 → La → L1→ O) is proposed based on results of charge difference distribution and experimental observation. The electron localization could directly activate the O2 and NO molecules and dramatically promote the production of activated species (e.g. O2- and OH radicals) and thus enhancing the photocatalytic efficiency. With the optimized electronic structure, the photocatalytic NO removal ratio of C N-O La is significantly increased from 35.8% of pristine g-C3N4 to 50.4% and it is stable for recycled runs. The in situ FT-IR spectra, in combination with ESR spectra and DFT calculations, unravel the conversion pathway of photocatalytic NO oxidation on C N-O La where some important reaction intermediates are discovered. This work could provide a fascinating modification strategy for carbon nitride and new insights into mechanistic understanding of 2D layered photocatalysts.