Platinum-decorated graphene: Experimental insight into growth mechanisms and hydrogen adsorption properties

Pt-functionalized graphene shows promise for near-ambient hydrogen storage due to graphene's potential as a hydrogen host and platinum's role as a catalyst for the hydrogen evolution reaction and spillover effect. This study explores Pt cluster formation on epitaxial graphene and its suitability for hydrogen storage. Scanning Tunneling Microscopy reveals two growth pathways. Initially, up to similar to 1 monolayer of Pt coverage, Pt tends to randomly disperse and cover the graphene surface, whereas the cluster height remains unchanged. Beyond a coverage of 3 monolayer, the nucleation of new layers on existing clusters becomes predominant, and the clusters mainly grow in height. Thermal Desorption Spectroscopy on hydrogenated Pt-decorated graphene reveals the presence of multiple hydrogen adsorption mechanisms. Two Gaussian peaks, which we attribute to hydrogen physisorbed (peak at 155 degrees C) and chemisorbed (peak at 430 degrees C) on the surface of Pt clusters are superimoposed on a linearly increasing background assigned to hydrogen bonded in the bulk of the Pt clusters. These measurements demonstrate the ability of Pt-functionalized graphene to store molecular hydrogen at temperatures that are high enough for stable hydrogen binding at room temperature.