Catalysis Today, Vol.335, 278-285, 2019
A computational study on linear and bent adsorption of CO2 on different surfaces for its photoreduction
The adsorption of CO2 on the surface of heterogeneous catalysts is crucial for the subsequent photoreduction reactions. As the direct one-electron reduction of CO2 is extraordinarily difficult because of the -1.9 V reduction potential, adsorption induced CO2 bending to form CO2 delta- is considered one efficient approach to decrease the overpotential of the intermediate formation during CO2 reduction. However, it is still unclear what material and surface are in favor of the formation of adsorption-induced bending of CO2, which is important for the design of active surfaces. Here we perform the first principle study on the adsorption of CO2 on the surface of some typical photocatalysts and co-catalysts. It is found that the CO2 bending upon adsorption can only occur on certain crystal surfaces of some materials, even on the perfect surface without any defects. If the exposed crystal surface has a linear metal-oxygen-metal (M-O-M) structure, the carbonate-like configuration upon CO2 adsorption may be easier to be formed than that on the other exposed surfaces. TiO2 (001), CeO2 (111), CeO2 (110) and MgO (100) seem more attractive among all the surfaces under study, as the bent CO2 configuration on these two surfaces are more stable than the linear one. Moreover, the barrier that CO2 changes from linear configuration to bent is relatively small. Our results are in good agreement with the experimental results that TiO2 (001) and MgO (100) exhibit high photocatalytic activity.