Theoretical investigation on the mechanism of CO₂ hydrogenation to methanol over single atom Ge promoter doped Cu(111) surface

In this work, we proposed a novel strategy, doping single atom Ge promoter to the Cu(111) surface, to overcome the shortcomings such as the difficulties in the adsorption and activation of CO2 molecules and the complex by-products produced in both the reverse water gas shift (RWGS) and the formate reaction pathway. The electron modulating effect of single atom Ge species on the reaction mechanism of CO2 hydrogenation to methanol over Ge-Cu(111) surface was detailly investigated by the density functional theory (DFT) method. The results show that the electron supply ability of Cu atoms adjacent to the single Ge atom is greatly enhanced due to the electron modulating effect of Ge species, which leads to the improved interaction between the CO2 molecule and the active interface: the adsorption energy of CO2 over the single atom Ge promoted Cu(111) surface was approximately 1.5 times that over the pure Cu(111) surface and approximately 2.4 times that over clustered Pd modified Cu(111) surface, respectively. The enhanced CO2 adsorption ability further resulted in a decline in the activation energy of the reaction rate control step for the RWGS pathway by about 20 kJ.mol(-1), meanwhile, there emerged three new potential RWGS reaction routes that only produced methanol. Moreover, the formate reaction pathway is kinetically inhibited over the Ge-Cu(111) surface, leading to the reduced by-products such as CO and hydrocarbons to improve both the selectivity of methanol in the CO2 hydrogenation to methanol reaction.