Photocatalytic CO2 reduction with water vapor to CO and CH4 in a recirculation reactor by Ag-Cu2O/TiO2 Z-scheme heterostructures

Abstract A ternary Z-scheme Ag-Cu2O/TiO2 catalyst was prepared by one-step chemical reduction method which was applied in photocatalytic CO2 reduction with water vapor under simulated sunlight in a recirculation reactor. The structure, morphology, photo absorption capacity and optoelectronic properties of the obtained samples were characterized by XRD, TEM, XPS, UV-vis DRS and Photoelectrochemical measurements. The photocatalytic activity tests showed that 0.5Ag-0.5Cu2O/TiO2 exhibited the highest production rate of CO (13.19 μmol/g/h) and CH4 (1.74 μmol/g/h) under simulated sunlight when compared to P25, 1Cu2O/TiO2 and 1Ag/TiO2. Mechanism studies by means of EPR technology testified that the improvement of photocatalytic performance was mainly due to the formation of Z-scheme heterojunctions between P25 and Cu2O, which facilitated the separation of photogenerated charges. The incorporation of Ag nanoparticles further enhanced the transfer of photogenerated carriers and the absorption of visible light, thus preventing the self-reduction of Cu2O and improving the photocatalytic CO2 reduction performance.