Kinetics, mechanism, and the influence of H2 on the CO oxidation reaction on a Au/TiO2 catalyst

We present results of a kinetic and in situ IR spectroscopic study, including isotope-labeling experiments, on the CO oxidation behavior over a highly active Au/TiO2 catalyst prepared via a novel synthesis procedure, and on the effect of H2 on the CO adsorption/reaction characteristics under conditions relevant for CO removal from CO-contaminated feed gases for polymer electrolyte fuel cells (PEFCs) via preferential CO oxidation (PROX). The results show that (i) H2 affects the CO oxidation, most probably by competing hydrogen adsorption on the Au nanoparticles and reaction with oxygen, which results in a significantly higher CO reaction order, that (ii) formate and carbonate species formed during the reaction represent (reaction inhibiting) side products, but do not take part in the reaction as reaction intermediate, at least not under present reaction conditions, and that (iii) the formation of formate and carbonate species is inhibited during reaction in a H2-rich atmosphere. This is tentatively attributed to the decomposition of these species by reaction with H2O, which is formed in the process gas upon H2 oxidation.