Bi2WO6/C3N4 S-Scheme Heterojunction with a Built-In Electric Field for Photocatalytic CO2 Reduction

Converting CO2 into renewable fuels by solar energy has been considered an ideal strategy to mitigate the climate crisis and address the fossil fuel depletion problem. However, severe charge carrier recombination and sluggish interfacial reaction dynamics make it a challenge to achieve high conversion efficiency. Herein, a unique 2D/2D step-scheme (S-scheme) photocatalyst of Bi2WO6/C3N4 (BWO/CN) is constructed by a facile electrostatic self-assembly strategy. The ultrathin 2D/2D heterostructure endowed the BWO/CN hybrid with abundant contact interfaces, short charge-transport distance, and relatively more accessible reaction sites. Besides, the differences of work function between CN and BWO induced the formation of a built-in electric field, resulting in much enhanced interfacial charge transfer/separation rates. As a result, the optimized BWO/CN heterojunction exhibits significantly improved photocatalytic performance toward CO2 reduction, which is approximately 2.8-fold higher than that of its CN counterpart. The accelerated S-scheme charge-transfer mechanism is systematically corroborated by X-ray photoelectron spectroscopy, photo-irradiated Kelvin probe force microscopy, and electron spin resonance. This research may provide a facile protocol for the rational design of an S-scheme face-to-face 2D/2D heterojunction for efficient CO2 conversion.