Construction of a hierarchical BiOBr/C3N4 S-scheme heterojunction for selective photocatalytic CO2 reduction towards CO

Abstract

Photocatalytic CO₂ reduction is an ideal strategy to simultaneously alleviate environmental concerns and address carbon neutrality; however, this process remains challenging because of the sluggish charge-carrier separation efficiency. Herein, we depict a unique hierarchical S-scheme heterojunction photocatalyst constructed via in situ growth of BiOBr nanosheets on microtubular C₃N₄ (denoted as BiOBr/TCN). The hierarchical structure provides sufficient active sites and an improved CO₂ uptake capacity, enabling enhanced catalytic reaction kinetics. The established S-scheme heterojunction endows the BiOBr/TCN photocatalyst with boosted charge carrier separation efficacy and retainment of the highest redox ability, which was corroborated by the density functional theory calculations and electron paramagnetic resonance analysis. Profiting from synergistic enhancement of charge separation and surface reactions, the synthesized BiOBr/TCN hybrid affords CO as the sole carbonaceous product with a production rate of 10.89 μmol g⁻¹ h⁻¹, which is approximately 8.1 times higher than that of bulk C₃N₄ under visible-light irradiation. This study presents a promising strategy for the development of effective S-scheme heterojunction photocatalysts for CO₂ reduction.