EPR Investigation on Electron Transfer of 2D/3D g‐C₃N₄/ZnO S‐Scheme Heterojunction for Enhanced CO₂ Photoreduction

Abstract Photocatalytic conversion of CO₂ into useful products is a promising technology from environmental and economic viewpoints. However, the efficiency of current photocatalytic materials is still unsatisfactory. In this work, a robust S‐scheme heterojunction composed of 3D ZnO hollow spheres wrapped by 2D g‐C₃N₄ layers is fabricated. The electrostatic attraction between both components not only facilitates the exfoliation of g‐C₃N₄ layers but also strengthens the photocatalyst framework. The prepared g‐C₃N₄/ZnO photocatalyst afforded an enhanced CH₄ production rate, which is ≈40 and 7 times higher than those of pure ZnO and g‐C₃N₄, respectively. The improved activity is attributed to the extended light absorption and suppressed charge carrier recombination. Moreover, apart from traditional techniques, electron paramagnetic resonance (EPR) is used to probe charge movement in the fabricated S‐scheme heterojunction. An observable shift of the relevant EPR peak is noticed after the construction of g‐C₃N₄/ZnO heterostructure, indicating the electron transfer process. This study sheds light on S‐scheme heterojunctions as efficient candidates for CO₂ photocatalytic conversion.