It is known that water structure stabilization happens over the H OPD hydrogen layer, and hence electrolyte-induced changes in water structure of interfacial may be behind the differences in the HER activity with different electrolytes. Raman and infrared (IR) studies show that H OPD coverage is higher in alkaline than in acidic medium, where it has been explained that H OPD is migrating to 3f2 sites of Pt in acidic medium giving half of the coverage whereas this kind of migration is forbidden in alkaline medium leading to a full coverage. Hence it is apparent that the structural changes in water are important to understand the changes in HER kinetics with pH as well as the nature of the electrolyte cations.