Our studies with other d 8 metals, Pt and Pd, found that Ni is unique in its OH binding energy of Ni which is much more favorable than that of Pd and especially Pt. From coverage calculations, we predict that significant OH coverage exists on Ni at alkaline HER conditions. These studies also revealed a significant difference in H2O dissociation. Ni was calculated to have a comparable or lower Volmer barrier despite its poor activity. We Ni was shown to have a more consistent solvation environment and a smaller free energy barrier when compared to OH-modified Ni. Our calculations offer a novel explanation of why such a metal/metal-compound heterostructure possesses a superior activity compared to that of its pure metal counterpart.