Hydrogen Spillover and Storage on Graphene with Single-Site Ti Catalysts

Hydrogen spillover and storage for single-site metal catalysts, including\nsingle-atom catalysts (SACs) and single nanocluster catalysts, have been\nelucidated for various supports but remain poorly understood for inert carbon\nsupports. Here, we use synchrotron radiation-based methods to investigate the\nrole of single-site Ti catalysts on graphene for hydrogen spillover and\nstorage. Our in-situ angle-resolved photoemission spectra results demonstrate a\nbandgap opening and the X-ray absorption spectra reveal the formation of C-H\nbonds, both indicating the partial graphene hydrogenation. With increasing Ti\ndeposition and H2 exposure, the Ti atoms tend to aggregate to form nanocluster\ncatalysts and yield 13.5% sp3-hybridized carbon atoms corresponding to a\nhydrogen-storage capacity of 1.11 wt% (excluding the weight of the Ti\nnanoclusters [1]). Our results demonstrate how a simple spillover process at Ti\nSACs can lead to covalent hydrogen bonding on graphene, thereby providing a\nstrategy for a rational design of carbon-supported single-site catalysts.\n