Do you think it’s a surface effect or a bulk effect? I remember seeing a couple of studies that used sintered metal as the lattice. One thing that sintering does is to incrase the surface area.
I think, more accurately, a thin layer effect. "Surface" is kind of a nebulously defined thing. IIRC, one of the earliest claims to high output was by an ex-Dow Chemical electrochemist (Patterson??), who used a palladium layer on plastic beads. Not exactly a high temperature system.