DFT Study of the Dissociation of H2O and H2 on ŠAl2O3 Supported Pt Clusters
Jennifer Synowczynski, Weapons and Materials Research Directorate, U.S. Army Research Laboratory, AMSRD-ARL-WM-MA, Aberdeen Proving Grounds, MD 21085-5069, Jan Andzelm, US Army Research Laboratory, Aberdeen, MD 21005, and Dion Vlachos, Director of Center for Catalytic Science and Technology (CCST), University of Delaware, Newark, DE 19716.
Alumina supported catalytic nanoclusters have been used to promote a variety of reactions including the steam reforming of methane and Fischer-Tropsch synthesis. Although there are many computational studies which detail the complete reaction mechanism for reactant and product species interacting with the catalytically active cluster, few studies consider the pathways that arise due to the combination of the cluster and support. One example of such a pathway is the ďinverse spilloverĒ effect which occurs when H2O chemisorbs or dissociates on the support forming mobile species which then migrate to the catalytically active particle and further promote oxidation reactions. This effect has been experimentally observed during the steam reforming of methane on alumina supported Rh clusters. Previously, we performed DFT/GGA barrier calculations for the molecular and dissociative adsorption of H2O on the ŠAl2O3 surface. Our results confirm that water prefers to dissociate but can also exist as molecularly chemisorbed H2O. The barriers to diffusion for the dissociated products on the order of 3 kcal/mol. In this paper, we build on our previous model for the adsorption / dissociation of H2O and H2 on the ŠAl2O3 Al terminated (0001) surface to include barrier calculations for new pathways that arise due to the interaction between the Pt cluster and the alumina support.