Elementary steps for CH4 reactions

Isotopic tracer pro on other metals (Ni, Ru, Rh, Ir, Pt). As a result, these steps become reversible during catalysis, because the sequence of elementary steps and their kinetic relevance, as well the effects of metal cluster size and supports, remain controversial, at least in part because of ubiquitous thermodynamic and trans-port corruptions of reaction rates, often measured at conditions near thermodynamic equilibrium. Our previous studies have addressed these mechanistic and practical matters for CH4 reforming with CO2 and H2O co-reactants and for CH4 decomposition on supported Ni, Ru, Rh, Pt, and Ir clus-unsaturated surface atoms, prevalent on small clusters, tend to sta-bilize C and H atoms and the transition states involved in C–H bond activation more effectively than more highly coordinated surface atoms on low-index surfaces. The extreme unsaturation of surface atoms at corners or edges may lead, however, to unreactive carbon, rendering such sites permanently unavailable at all reforming reaction conditions. Supports did not influence C–H activation turnover rates, except through their effect on metal dispersion, as expected from the sole kinetic relevance of C–H bond activation steps and from their exclusive occurrence on metal clusters. Co-reactant activation steps and all elementary steps involved i