As shown in the first section, S can diffuse from the Ni3S2 phase to pure Ni, creating a surface modified Ni-S phase. In contrast, pure Ni catalysts will be covered by some amount of OH in alkaline conditions. S and OH occupy the same sites on the metal surface and so these surface modified states are mutually exclusive. The lesser hydrogen bonding consistency on the OH surface is a likely origin for the inferior activity of pure Ni. The adsorbed *OH disrupts the hydrogen bond network in the interface in a way that adsorbed *S does not. *OH partakes in hydrogen-bonding and *S simply blocks the surface.