Bonding states of hydrogen for supported Ti clusters on pristine and defective graphene

Abstract

To determine whether graphene-supported Ti clusters can synergistically store hydrogen through Kubas and spillover effect, we systematically investigate the growth pattern of Tin (n = 1–10) clusters on pristine and defective graphene and analyze multiple types of bonding states of hydrogen in detail. For pristine graphene, the most stable Tin (n = 1–10) clusters are the quasi-planar structure except for supported Ti4 and Ti5. The Ti dissociation energies and the binding energy of Tin clusters gradually increase with increasing n, which indicates that larger Tin clusters tend to form. Efficient spillover will occur on single-site Ti Catalysts at low hydrogen concentration due to the lower hydrogen spillover energy barrier (3.05 eV), while the energy barrier of hydrogen migration from Tin (n = 2–7) clusters to graphene on the cluster is 5.34–6.82 eV. The Ti: H ratio is a maximum of 1:8 for the single-site Ti catalyst, while decreases with the Tin cluster increases. Therefore, the pristine graphene-supported Ti nanoclusters are more suitable as substrates for hydrogen adsorbent rather than spillover. The introduced defects make Tin clusters have three-dimensional conical configurations from n = 4. Ti3 and Ti6 are the most stable clusters. Moreover, the migration energy barriers of H atoms on them decrease from 6.54 eV to 6.82 eV–4.32 eV and 3.42 eV, respectively. Our results explain recent experimental phenomena [Appl Phys Lett 2015; 106: 083,901. ACS Energy Lett 2022; 7 (7): 2297–2303] in depth at the molecular level.