As already reported, the hydrogen evolution from neutral pH aqueous electrolytes by hot electrons in Al/Al2O3/Ag junctions at the silver/electrolyte interface is observed only when the silver electrode is weakly "activated" (roughened). After a short description of all relevant phenomena we present a simple model which is based on the increase of the average penetration depth of the hot electrons into the electrochemical double layer by scattering at the surface roughness of the silver(lll) face. This leads to a more anodic onset of the hydrogen evolution from the dissociation of water, but only at an activated surface. The model also explains why activation does not reduce the overpotential of the normal hydrogen evolution.