Density Functional Kinetic Monte Carlo Simulation of Water-Gas Shift Reaction on Cu/ZnO

We describe a density functional theory based kinetic Monte Carlo study of the water-gas shift (WGS) reaction catalyzed by Cu nanoparticles supported on a ZnO surface. DFT calculations were performed to obtain the energetics of the relevant atomistic processes. Subsequently, the DFT results were employed as an intrinsic database in kinetic Monte Carlo simulations that account for the spatial distribution, fluctuations, and evolution of chemical species under steady-state conditions. Our simulations show that, in agreement with experiments, the H-2 and CO2 production rates strongly depend on the size and structure of the Cu nanoparticles, which are modeled by single-layer nano islands in the present work. The WGS activity varies linearly with the total number of edge sites of Cu nano islands. In addition, examination of different elementary processes has suggested competition between the carboxyl and the redox mechanisms, both of which contribute significantly to the WGS reactivity. Our results have also indicated that both edge sites and terrace sites are active and contribute to the observed H-2 and CO2 productivity.