Predicting CO2 adsorption and reactivity on transition metal surfaces using popular density functional theory methods
In this work, with Ni (110) as a model catalyst surface and CO2 as an adsorbate, a performance study of Density Functional Theory methods (functionals) is performed. CO being a possible intermediate in CO2 conversion reactions, binding energies of both, CO2 and CO, are calculated on the Ni surface and are compared with experimental data. OptPBE-vdW functional correctly predicts CO2 binding energy on Ni (−62 kJ/mol), whereas CO binding energy is correctly predicted by the rPBE-vdW functional (−138 kJ/mol). The difference in computed adsorption energies by different functionals is attributed to the calculation of gas phase CO2. Three alternate reaction systems based on a different number of C=O double bonds present in the gas phase molecule are considered to replace CO2. The error in computed adsorption energy is directly proportional to the number of C=O double bonds present in the gas phase molecule. Additionally, both functionals predict similar carbon–oxygen activation barrier (40 kJ/mol) and equivalent C1s shifts for probe species (−2.6 eV for CCH3 and +1.5 eV CO3−), with respect to adsorbed CO2. Thus, by including a correction factor of 28 kJ/mol for the computed CO2 gas phase energy, we suggest using rPBE-vdW functional to investigate CO2 conversion reactions on different metals.