Revealing the Mechanism of Converting CO into Methanol by the CuO and Oxygen Vacancy on MgO: Experiments and Density Functional Theory.

Given the great significance of defect and Cu compounds for the reduction of CO as well as the few reaction mechanisms of converting CO into different hydrocarbons, the effects of oxygen vacancies and CuO on the reduction of CO were thoroughly investigated, and possible mechanisms were also proposed. A series of CuO/O-MgO catalysts were synthesized for photothermal catalytic reduction of CO to methanol under visible-light irradiation, among which the 7%CuO/O-MgO composite exhibited the best reduction activity and the yield of methanol was 19.78 μmol·g·h. The successful composite of CuO and O-MgO can yield a loose and porous nanosheet, uniform distribution, favorable absorbance and photoelectric performance, and increased specific surface area and adsorption ability of CO, which are all vital to the adsorption and conversion of CO. The introduction of oxygen vacancy and CuO not only promotes the adsorption of CO but also provides more electron-triggered CO activation. Density functional theory (DFT) calculation was also performed to reveal the reaction mechanism for effective enhanced CO reduction to ethanol or methanol by the comparison of CuO/MgO and CuO/O-MgO composites, illustrating the reaction pathways of different products. By comparing the key steps in determining the selectivity of C or C, the kinetic barriers of obtaining CHOH for the CuO/O-MgO composite with CHOH as the main product were found to be lower than those of generating CH*, while the opposite is true for CuO/MgO composites, whereby it may be easier to obtain more C products. These insights into the reaction mechanism of converting CO into different hydrocarbons are expected to provide guidance for the further design of high-performance photothermal catalytic CO reduction catalysts.