DFT Study of the Water-Gas Shift Reaction and Coke Formation on Ni(111) and Ni(211) Surfaces

We report for the first time results of a systematic density functional theory (DFT) study of the water-gas shift (WGS) reaction and coke formation pathways on Ni(111) and Ni(211) surfaces, consisting of 21 elementary-like steps and 12 surface species. Bronsted-Evans-Polanyi correlations are proposed for dehydrogenation and C-O bond breaking reactions on flat and stepped surfaces. The DFT results suggest that the flat surface is slightly more active for the WGS reaction, which occurs mainly via the carboxyl pathway with the CO* + OH* reversible arrow COOH*+* as the rate determining step. On the stepped surface, beyond the carboxyl pathway, the DFT energetics indicates that a parallel route via formate and formyl intermediates is favored. Ni(111) has a much lower activity for C-O bond breaking, and thus, flat surfaces are less susceptible to deactivation by coke.