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

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.