Fig. 1: Schematic illustrations of the interfacial electronic configurations and hydrogen spillover phenomenon in HSBB catalysts.
From: A fundamental viewpoint on the hydrogen spillover phenomenon of electrocatalytic hydrogen evolution

Evac = vacuum energy, Ec = conduction band, Ev = valence band, Ef-M = Fermi level of metal, Ef-al Fermi level of alloy, Ef-S Fermi level of support.