Graphitic carbon nitride/La, Rh co-doped SrTiO₃ S-scheme heterojunction for photocatalytic CO₂ reduction

Photocatalytic reduction of CO₂ has attracted considerable interest owing to its potential to resolve the energy and environmental problems. Nevertheless, the lack of proficient photocatalysts has restricted the application of solar-driven photocatalytic CO₂ reduction. Herein, we reported an S-scheme heterojunction by combining g-C₃N₄ with La³⁺ and Rh³⁺ co-doped SrTiO₃ through the electrostatic self-assembly method for the efficient photocatalytic CO₂ reduction. In comparison with g-C₃N₄, the as-prepared CN/LRSTO-30 wt% S-scheme heterojunction not only possesses a broadened visible-light response due to the defect states in La, Rh co-doped SrTiO₃ induced by co-doped La³⁺ and Rh³⁺ but also has more adsorption sites for the capture and activation of CO₂ molecules. Additionally, separation and transfer efficiency of the photoinduced charge carriers is much enhanced in the CN/LRSTO-30 wt% S-scheme heterojunction via its robust internal electric field, which is firmly demonstrated by in situ irradiation X-ray photoelectron spectroscopy technology. Consequently, the prepared S-scheme heterojunction achieves impressive photocatalytic CO₂ reduction performance with an average CO and CH₄ evolution rate of 4.1–1.8 μmol·g⁻¹·h⁻¹, respectively, which are ~ 1.9 and  ~ 22.5-fold higher than those of pure g-C₃N₄. This study provides innovative perspectives on the design of creative S-scheme heterojunctions for applications in photocatalytic CO₂ reduction.