Identification of hydrogen species on Pt/Al2O3 by in situ inelastic neutron scattering and their reactivity with ethylene

Abstract

Hydrogen (H) species adsorbed on catalyst surfaces are key intermediates in catalytic hydrogenation reactions over supported metal catalysts. However, individual identification of H species on the metal catalysts has not been established to date. Here, we elucidated the H species on Pt/Al₂O₃ by the combination of in situ inelastic neutron scattering (INS) and density functional theory (DFT). Several H species in the presence of H₂ were successfully identified at different sites on the Pt surface and Al₂O₃ support. The in situ INS and FT-IR measurements revealed that the hydride/atop Pt–H, bridged perimeter/terrace Pt–H–Pt, and threefold Pt₃–H are active intermediates in the C₂H₄ hydrogenation reaction, whereas the edge Pt–H–Pt is a rather inert species. In addition, the in situ measurements indicate that the Al₂O₃ itself acts as hydrogen storage material by mediating AlO–H and Al–H–Al species, which serve H species in the C₂H₄ hydrogenation reaction.