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.