Understanding the role of Ga on the activation mechanism of CO2 over modified Cu surface by DFT calculation

Ga-containing catalysts show excellent performance in CO2 catalytic utilization. In this research, activation mechanisms of CO2 on Cu Surface modified by Ga with different forms (Cu, Cu8Ga1, Cu6Ga3, and Ga2O3@Cu) were systematically studied by DFT calculations. Combining the thermodynamics with chemical kinetics, the roles of interfacial effect for CO2 activation were revealed. The reaction energy barrier was significantly reduced at the interface between metal surface and Ga2O3. CO2 preferentially activates through CO2 -> CO2*-> HCOO* at the interface. For Ga2O3 supported Cu catalyst, CO2 was transformed into chemisorbed CO2*, while for Cu, Cu8Ga1 and Cu6Ga3 catalysts, CO2 was behaving as physical adsorption. Millikan atomic charge and CO2 charge density difference for different catalyst surfaces were obtained, and it was found that the two oxygen atoms of CO2 gained the same charges for alloy surfaces while at the interface obtained different charges. Two oxygen atoms gained different charges showing the charge imbalance of the CO2 molecule, which was more favorable to the activation of C = O. The interfacial effect formed between the oxide of Ga and the catalyst surface promotes the activation of CO2 molecule.