Boosted charge separation in direct Z-scheme heterojunctions of CsPbBr3/Ultrathin carbon nitride for improved photocatalytic CO2 reduction

Abstract

Realizing CO₂ reduction with H₂O oxidation on g-C₃N₄-based photocatalysts is quite promising yet challenging. Herein, an efficient direct Z-scheme heterostructure of ultrathin CsPbBr₃/g-C₃N₄ nanosheets is fabricated via a simple electrostatic self-assembly process, resulting in an effective photocatalytic reduction of CO₂ to CH₄ (184.0 μmol g⁻¹) and CO (105.2 μmol g⁻¹) with oxidation of H₂O under AM 1.5G irradiation. Notably, in situ X-ray photoelectron spectroscopy (XPS) analysis demonstrated that a direct Z-scheme charge transfer mechanism at the CsPbBr₃ and g-C₃N₄ interface is enabled, thereby achieving efficient charge separation and high redox potentials to drive photocatalytic CO₂ reduction and H₂O oxidation synchronously. Isotopic labelling experiments revealed that the adsorbed water is activated to release H atoms and eventually assists the CO₂ reduction. Theoretical calculations further revealed that the p orbitals of Pb atoms hybridize with the 2π* orbitals of CO₂ molecules, strengthening the affinity of CO₂ and weakening the binding strength. Moreover, overlapping between Pb p orbitals and 5σ orbitals of CO molecules promote the protonation of CO* intermediates. This work provides an in-depth understanding and guidance for constructing high-efficiency catalysts for CO₂ reduction with H₂O oxidation.