In-situ growth of ultrafine ZnO on g-C3N4 layer for highly active and selective CO2 photoreduction to CH4 under visible light

Photocatalytic CO2 reduction to solar fuels is considered as a promising strategy to address the global warming and energy shortages. Herein, a novel method is proposed to prepare g-C3N4/ZnO nanocomposites via refluxing zinc salt methanol solution containing pre-formed g-C3N4 with KOH methanol solution as precipitating agent. Some in-situ grown ultrafine ZnO nanoparticles are decorated on ultrathin g-C3N4 layers with well-defined interface, which not only causes efficient charge transfer and separation, but also creates more active sites for CO2 adsorption and activation. The resultant g-C3N4/ZnO composites demonstrate significant enhanced CO2 photoreduction activity and selectivity for CH4 production under visible light irradiation, and the optimal g-C3N4/ZnO composite delivers the best overall photoactivity (158.4 μmol g−1 h−1) with CH4/CO production rates of 19.8/0.37 μmol g−1 h−1, which is 9.42 times higher than that of g-C3N4 alone. This work provides an ideal synthetic strategy for g-C3N4-based hybrid materials with highly efficient CO2 photoreduction.