Hydrogen Adsorption on Mixed Platinum and Nickel Nanoclusters: The Influence of Cluster Composition and Graphene Support

Abstract

The physical and chemical properties of transition metal nanoclusters have been extensively investigated. In particular, we study the energetics of the mixed clusters Pt4−n Ni n , focusing on the binding energy of the clusters E bind to a graphene support, and the hydrogenation energy E ads in both the gas-phase and the graphene-supported clusters. For each cluster composition, the cluster can bind to graphene in either a face-on or an edge-on configuration, and in each of these orientations, binding can occur through different atoms; we explore these binding configurations comprehensively. We discuss the variation of E bind and E ads with respect to the composition of the cluster and the binding configuration of the cluster to the graphene support. Our results show that hydrogen is generally chemisorbed at a Pt site and physisorbed at a Ni site, with a dependence of the adsorption energy upon the composition and the adsorption configuration. Compared with the gas-phase cluster, the chemisorption energies are generally reduced, whereas the physisorption energies are generally increased when the cluster is supported on graphene. We show that the reduction in chemisorption energies can be understood in terms of the reduction in the intracluster bond strength and the binding energy to graphene, whereas the increase in physisorption energies can be understood in terms of an increase in the charge transferred to the adsorbed hydrogen. We also show that the binding energy to graphene depends upon composition, both through the elemental identity of the atoms binding to graphene and also through the strength of the intracluster bonding. In general, E bind is reduced upon hydrogen adsorption on the cluster. In some cases, this changes the relative binding energies of different binding configurations, thus leading to a change in the most stable cluster orientation when hydrogen adsorption occurs. Our results show that E ads varies through a significant range with cluster composition and that this variation can be effectively understood through a consideration of the changes in localized charges on the hydrogen, the cluster atoms, and the graphene upon hydrogen adsorption. This dependence should be of broader relevance to other mixed transition metal clusters.

In situ thermolysis of Pt-carbonyl complex to form supported clean Pt nanoclusters with enhanced catalytic performance

“…The turnover frequency (TOF) of Pt-1 nm/rGO (TOF: mol number of NB transformed per mol per h) reaches 975.4 h −1 . This value is higher than the previously reported data for heterogeneously catalyzed dehydrogenation of NB [8,37,38]. The conversion ratio is 81.55%, 36.85%, and 4.92% over Pt-1.4 nm/rGO, Pt-1.7 nm/rGO, and Pt-2.4 nm/rGO within the same reaction period, respectively; the corresponding TOFs are 796.5, 359.4, and 4.8 h −1 .…”

Coordination chemistry on carbon surfaces

“…Moreover, the functionalized defective graphene exhibits semiconducting or half-metallic nature, which is dependent on the values of n and m. Meanwhile, most of decorated defective graphenes exhibit nonzero magnetic moments, contributed mainly by the adsorbed clusters. For Pt 3 Ni, Pt 2 Ni 2 , and PtNi 3 clusters adsorbed on graphene, DFT calculations have predicted binding energy between −0.02 and −0.95 eV [568]. The binding energy and relative stability of the supported clusters depend not just upon the composition but also upon how the cluster is adsorbed onto graphene, whether in the face-on configuration or the edgeon configuration.…”

A theoretical study of the effects of transition metal dopants on the adsorption and dissociation of hydrogen on nickel clusters

“…Nevertheless, there is ambiguity about their structures and properties, as they possess complicated electronic ground state structures with magnetic moments due to the presence of d electrons . In recent years, LTMs doped on Ni clusters have received attention due to their potential applications in catalysis . However, there has been a limited number of theoretical investigations on the mixed systems containing nickel.…”