DFT Insights into Comparative Hydrogen Adsorption and Hydrogen Spillover Mechanisms of Pt4/Graphene and Pt4/Anatase (101) Surfaces

A comparative study of the hydrogen spillover phenomenon on pristine graphene and anatase (101)-supported Pt-4 catalysts has been carried out by using density functional theory with Hubbard correction (DFT + U) and dispersion correction (Grimme-D3). The adsorption of the H-2 molecule causes no dissociation on graphene but dissociation with nearly zero adsorption energy on anatase (101). This emphasizes the need for a metal catalyst for H-2 dissociation to aid the stronger chemisorption of hydrogen atoms or protons on the substrate. The metal-support interaction is different for both substrates as Pt-4 shows p-type doping for graphene and n-type doping for anatase (101) surfaces with binding energies of -2.16 and -5.82 eV, respectively. The differing nature of H-2 adsorption and metal-support interactions lead to different hydrogen spillover phenomena for the two supports. Hydrogen spillover is unlikely to occur on Pt-4/graphene even at high hydrogen coverage (24H atoms per Pt-4) but has a tendency to take place on anatase (101) at medium hydrogen coverage (10H atoms per Pt-4) from the perspectives of both thermodynamics and kinetics.