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 approximate to 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.