Synergistic effect of hierarchical structure and S-scheme heterojunction over O-doped g-C₃N₄/N-doped Nb₂O₅ for highly efficient photocatalytic CO₂ reduction

Reasonable construction and engineering of optimal hierarchical photocatalysts have garnered great attention in terms of promoting CO₂ photoreduction into fuel production. Herein, we introduce a novel 3D O-doped g-C₃N₄/N-doped Nb₂O₅ (OCNNb) S-scheme heterojunction fabricated using control of each material's surface charge-induced heteroaggregation for photocatalytic CO₂ reduction (PCR). The optimized sample converts CO₂ with substantially greater rates (the sum production rate of CO and CH₄) than the blank control, i.e., O-doped g-C₃N₄ (OCN) and N-doped Nb₂O₅ (NNBO). The enhanced photocatalytic efficiency can not only be ascribed to the prevention of photogenerated charge carrier recombination mediated by the S-scheme heterojunction but also to the high specific surface areas and abundance of active sites. In the meantime, work function measurement, in situ irradiated, X-ray photoelectron spectroscopy and electron paramagnetic resonance (EPR) studies confirm the S-scheme photogenerated charge transfer mechanism. This study offers a useful approach for fabricating extremely effective heterojunction photocatalysts to convert solar fuels.