Water-gas-shift reaction over nickel catalysts: DFT studies and kinetic modeling

Density functional theory (DFT) calculations were used to study the mechanism of water gas shift (WGS) reaction on Ni (111) surfaces. Three sets of elementary reactions based on the formate intermediate and oxidation-reduction mechanisms are considered in this study. Formate intermediate is produced via dissociation and non-dissociation adsorption of H2O in the proposed mechanisms. The adsorption energy for all surface species and the activation barriers for the rate-determining steps in these WGS mechanisms were calculated. The overall reaction rates were developed based on the considered mechanisms. Based on the Sabatier principle, the effects of CO and H2O adsorption energies on the activation energy of the rate-determining reactions in the proposed mechanisms are considered. According to the calculated overall activation energies, the formate intermediates produced from the reaction between adsorbed H2O and CO species provide the best condition for the overall WGS reaction.