Alumina-supported cobalt, nickel, and copper single-atom catalysts for CO to CO2 conversion; a comparative DFT study

In the present work, high-precise DFT calculations were employed to study the mechanistic pathways for CO to CO2 conversion using cobalt, copper, and nickel single-atom catalysts (SACs) on γ-alumina surface. In this lineو the comparison between the catalytic abilities of these SACs was made and the effect of the spin multiplicity of the catalyst on its potencies was investigated. DFT calculations showed that the most stable status for single-atom metals such as nickel, copper, and cobalt in the spin states are, respectively, 3, 2 & 4. Moreover, regarding the resulting data of DFT calculations and method along with the basis set M06-2×/SVP, it was identified that the single-atom catalyst, nickel, has the most efficiency in the oxidation reaction from CO to CO₂. It was also specified, through the calculations of the solvent effects (for water and methanol) and their comparison with the gas phase, that this reaction is better performed in the gas phase. These results help realize the theoretical mechanisms and the former empirical results making a necessary introduction for designing more single-atom catalysts with a high degree of efficiency based on alumina.