In-situ fabrication of Cu3(MoO4)2(OH)2 films decorated with MO (M=Zn, Cu, and Ni) for CO2 photoconversion into value-added compounds

Abstract CO2 photoreduction is an emerging technology to produce value-added compounds using abundant resources such as CO2, H2O, sunlight, and photocatalyst materials. Here, Cu3(MoO4)2(OH)2 (CMO) films were proposed as photocatalysts for CO2 photoconversion into value-added compounds, such as methanol, formic acid, and hydrogen. The CMO films were decorated with simple oxides MO (M=Zn, Cu, and Ni) by an in-situ microwave-hydrothermal method. The CMO films exhibited a bar morphology, high crystallinity, band gap suitable for solar-light activation (2.8 eV), and valence and conduction band potential of 1.3 eV and 1.5 eV vs NHE, respectively. After decoration with the simple oxides, the films retained the bar morphology and resulted in a more efficient charge transfer by forming type-I heterostructure between Cu3(MoO4)2(OH)2 and CuO; while, type-II heterostructures were produced between CMO and NiO and ZnO. The CO2 was photoconverted to HCOOH and CH3OH in the liquid phase using CMO reference and the decorated films as photocatalysts. Cu3(MoO4)2(OH)2 decorated with CuO (CMO/Cu) favored the production of 155 µmol g−1 HCOOH, 109 µmol g−1 for CH3OH, and 127 µmol g−1 H2 after 1 h under visible-light irradiation. The yields obtained were up to 8 times higher than other conventional photocatalysts. The stability and recyclability of the films were demonstrated after three consecutive cycles. The photocatalytic activity for value-added compounds production increased as follows: CMO/Cu > CMO/Ni > CMO/Zn > CMO, associated to a higher CO2 adsorption, 2D morphology, adequate conduction band potential, and a more efficient charge transfer.