2D/2D BiVO4/CsPbBr3 S-scheme heterojunction for photocatalytic CO2 reduction: Insights into structure regulation and Fermi level modulation

Heterojunction construction is a universal and effective approach to achieve high-efficiency photocatalysts. Towards these well-designed heterojunctions, modulation on steering dynamic charge transfer holds great promise in further performance stimulation. Herein, 2D/2D BiVO 4 /CsPbBr 3 S-scheme heterojunctions, of which CsPbBr 3 nanosheets (NSs) are in-situ face-to-face grown onto BiVO 4 NSs, are designed as cornerstones for further carrier managements. Briefly, with controllable heterostructure regulation, an intimate heterointerface between BiVO 4 and CsPbBr 3 NSs with similar size can be obtained accompanied with a maximally intensified interfacial interaction, largely boosting charge transfer across the interfacial conjunction. Moreover, by further tailoring the intrinsic O vacancy ( V O • • $V_O^{\mathrm{•}\mathrm{•}}$ ) of BiVO 4 , the gradient Fermi level shift towards its valence band is finely tuned, yielding an enlarged Fermi level gap and an enhanced internal electric field (IEF) over BiVO 4 /CsPbBr 3 heterojunctions. Such an intensified IEF provides a powerful driving force for directional charge migration, resulting in high charge separation and utilization efficiency. Hence, the optimized BiVO 4 /CsPbBr 3 S-scheme heterojunction features desirable accelerated dynamic carrier mobility, delivering comparably high CO 2 -to-CO conversion with a turnover number (TON) near 230 without any co-catalyst or sacrificial agent. The accelerated S-scheme charge transfer mechanism is revealed in detail by X-ray photoelectron spectroscopy (XPS), theoretical calculations, photo-irradiated Kelvin probe force microscopy and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).