CO₂ activation dominating the dry reforming of methane catalyzed by Rh(111) based on multiscale modelling

Abstract

The dry reforming of methane (DRM) converts two greenhouse gases (CH4 and CO2) to syngas (CO/H2). Rh-based catalysts are among the most active DRM catalysts, but they still need to be fully understood at the atomic level. In this work, we evaluated the Rh(111)-catalyzed DRM via periodic density functional theory and kinetic Monte Carlo (kMC) simulations, accounting for lateral interactions. The kinetic model consisted of 38 elementary reactions, including adsorption, desorption, and surface chemical reactions. The reaction network considered both the formation of the DRM products and the competitive reverse water-gas shift reaction. kMC simulations indicated direct CO2 activation takes place, yielding CO* and O*. The CH oxidation path (CH* + O*) was the preferred route to obtain the second CO molecule, and the water formation minimally affected the final H2/CO ratio. The catalytic system displayed Arrhenius behavior at different temperatures with an apparent activation energy of 53 kJ mol−1. The degree of rate control analysis identified CO2 activation as the dominant step in Rh(111)-catalyzed DRM, with no evidence of catalyst deactivation. Our study underscores the utility of multiscale modeling for a comprehensive understanding of heterogeneous catalysts from a bottom-up approach.