Reaction class-based frameworks for heterogeneous catalytic systems

Abstract

A systematic and self-consistent approach is applied to study the combustion of hydrogen and syngas over platinum using coupled detailed gas phase and surface reaction mechanisms. The surface chemistry is derived using a reaction class-based framework comprising variational transition state theory (VTST), two-dimensional collision theory and the unity bond index-quadratic exponential potential for barrier heights. The latter approach is augmented by the inclusion of more accurate data, such as the heat of adsorption of CO, and VTST is used to systematically remove the need for the surface sticking coefficients associated with adsorption and desorption processes. Transition-state theory estimates for several reaction classes are produced by combining the M06 family of density functionals with the Stuttgart/Dresden effective core potential for metal atoms. The developed method reproduces experimental data with an accuracy comparable or better than the previously used collision theory approach and without the reliance on experimental parameters. The presented framework is well-suited for the efficient generation of novel heterogeneous reaction mechanisms and also serves to identify key parameters where high accuracy ab initio methods may be required. The latter is exemplified via the sensitivity of selected results to the adsorption of carbon monoxide on platinum.