Studies of Z-scheme WO3-TiO2/Cu2ZnSnS4 ternary nanocomposite with enhanced CO2 photoreduction under visible light irradiation

To date, the rapid increase of the CO2 concentration in the Earth's atmosphere is one of the primary causes of global warming, which leads to other environmental issues; however, the photocatalytic CO2 reduction is a process that offers environmental protection and valuable solar fuels generation simultaneously. Yet, the high CO2 activation barrier and inefficient proton supply are the main challenges, which substantially hamper the photo-conversion efficiency over heterogeneous catalysts. Herein, a Z-scheme mesoporous WO3-TiO2/CZTS ternary photocatalyst was synthesized through a two-stage strategy, and the photoreduction of CO2 with H2O vapor was carried out under the visible light irradiation. A synergistic effect among WO3, TiO2 and CZTS over CO2 reduction was observed by anchoring the CZTS over WO3-TiO2 nanocomposite. The ternary composite showed the enhanced CO/CH4 yield rates of 15.37/1.69 μmol h−1 g−1, which was significantly higher than that of pristine TiO2 (0.44/0 μmol h−1 g−1) and WO3-TiO2 composite (5.39/ 0.34 μmol h−1 g−1), attributing the high surface area with greater light absorption and suppressed the electron–hole recombination as a result of the intrinsic p–n heterojunction nature of the material. The apparent quantum efficiency was estimated to be 0.52 %. In addition, the possible reaction mechanism and pathways of photocatalytic CO2 reduction with H2O over heterogeneous catalysts were also presented.