Novel photocatalytic activity of Cu@V co-doped TiO2/PU for CO2 reduction with H2O vapor to produce solar fuels under visible light

Abstract

In this study, Cu and V co-doped TiO2 deposited on polyurethane (Cu@V-TiO2/PU) was synthesized as a catalyst for the reduction of CO2 with H2O vapor to preferentially produce CH4 as a valuable solar fuel under visible light. The Cu and V dopants defected into the TiO2 lattice, leading to the formation of Ti3+ and oxygen vacancies in the lattice. The Ti3+ formed in the doped TiO2 lattice created an intermediate band between the valence band and the conduction band of TiO2, leading to an increase in the electron–hole pair separation efficiency of TiO2. The oxygen vacancies existing on the surface of the photocatalyst could induce new adsorption sites to adsorb CO2. The generated electrons and holes reacted with the adsorbed CO2 and with H2O vapor to produce CO and primarily CH4. Therefore, the Cu@V-TiO2/PU photocatalysts successfully utilized visible light as the energy source and H2O vapor as a reductant to reduce CO2 to CO and CH4. The Cu@V-TiO2/PU photocatalysts also supplied sufficient electrons and holes for the selective reduction of CO2 to CH4 rather than CO. The 2Cu@4V-TiO2/PU photocatalyst, with Cu/TiO2 and V/TiO2 ratios of 2 and 4wt.%, respectively, exhibited the highest photocatalytic activity for CO2 conversion into solar fuels. The production rates of CH4 and CO produced from the CO2 reduction by the 2Cu@4V-TiO2/PU photocatalyst under visible light were 933 and 588μmolg−1cat.h−1, respectively.