A DFT and KMC Based Study on the Mechanism of Water Gas Shift Reaction on Pd(100) Surface

We present a combined density functional theory (DFT) and Kinetic Monte Carlo (KMC) study of thewater gas shift (WGS) reaction on the Pd(100) surface. We propose a mechanism comprising both theredox and the associative pathways for the WGS within a single framework, which consists of seven coreelementary steps, which in turn involve splitting of a water molecule followed by the production of an Hatomand an OH-species on the Pd(100) surface. In the following steps, these intermediates thenrecombine with each other and with CO leading to the evolution of CO2, and H2. Seven other elementarysteps, involving the diffusion and adsorption of the surface intermediate species are also considered fora complete description of the mechanism. The geometrical and electronic properties of each of thereactants, products, and the transition states of the core elementary steps are presented. We also discussthe analysis of Bader charges and spin densities for the reactants, transition states and the products ofthese elementary steps. Our study indicates that the WGS reaction progresses simultaneously via thedirect oxidation and the carboxyl paths on the Pd(100) surface.