Constructing Z-scheme WO3/C3N4 heterojunctions with an enlarged internal electric field and accelerated water oxidation kinetics for robust CO2 photoreduction

Abstract

The solar-driven conversion of CO₂ into value-added fuels is regarded as one of the most promising strategies to address the increasing greenhouse effect and energy crisis. However, severe charge recombination and sluggish H₂O oxidation kinetics lead to its low efficiency. Herein, a Z-scheme WO₃/C₃N₄ heterojunction was constructed to overcome these issues, with C₃N₄ nanosheets (NS) and WO₃ NS acting as the CO₂ reduction centers and H₂O oxidation booster, respectively. Driven by the enlarged internal electric field, charge separation and migration in the WO₃/C₃N₄ heterojunction are promoted. Meanwhile, the WO₃ NS provide highly oxidative photoinduced holes to accelerate H₂O oxidation kinetics. Due to these advantages, the CO and CH₄ yields of the optimal sample reached 9.4 μmol g⁻¹ h⁻¹ and 2.6 μmol g⁻¹ h⁻¹, respectively, being approximately 4.5 times and 7.2 times that of the pristine C₃N₄ NS. Overall, this work contributes to an in-depth understanding of the Z-scheme mechanism and offers a feasible approach to simultaneously modulate the charge separation and surface reaction for enhancing the efficiency of photocatalytic CO₂ reduction.