Multiscale Approach to the Dissociative Adsorption of Oxygen on a Highly Dispersed Platinum Supported on gamma-Al2O3

The understanding of the reactivity of supported platinum with oxygen is of paramount relevance in heterogeneous catalysis, inter alia. We present here a multiscale investigation of the interaction of highly dispersed Pt/gamma-Al2O3 catalysts with O-2, through the combination of temperature-programmed desorption (TPD) experiments, ab initio simulations on a model Pt-13/gamma-Al2O3 cluster, and kinetic simulations of the TPD, thanks to data obtained from ab initio calculations. The specific behavior of the sub-nanometric platinum particles is benchmarked against the one of the ideal Pt(111) surface, as predicted by similar ab initio-based kinetic modeling. This approach reveals a fully different reactivity of highly dispersed Pt nanoparticles with respect to Pt(111), with a much higher capacity of oxygen storage for given temperature and P(O-2) conditions. In a large operating conditions interval, the Pt-13 clusters are converted into an oxide, whose stoichiometry is close to PtO2, but with a very specific hemispherical shape. Pt-cluster-O-alumina and O-cluster-Al-alumina bonds ensure a very strong interaction of these clusters with the support. The kinetic scheme built upon ab initio data to simulate TPD experiments allows to attribute the highest desorption temperatures reached experimentally to highly dispersed particles, from Pt13O20 to Pt13O4 clusters, through Pt13O16 and Pt13O10 intermediates.