Engineering a Local Free Water Enriched Microenvironment for Surpassing Platinum Hydrogen Evolution Activity.

Manipulating the catalyst-electrolyte interface to push reactants into the inner Helmholtz plane (IHP) is highly desirable for efficient electrocatalysts, however, it has rarely been implemented due to the elusive electrochemical IHP and inherent inert catalyst surface. Here, we propose the introduction of local force fields by the surface hydroxyl group to engineer the electrochemical microenvironment and enhance alkaline hydrogen evolution activity. Taking a hydroxyl group immobilized Ni/Ni ₃ C heterostructure as a prototype, we reveal that the local hydrogen bond induced by the surface hydroxyl group drags 4-coordinated hydrogen-bonded H ₂ O molecules across the IHP to become free H ₂ O and thus continuously supply reactants forcatalytic sites catalytic sites. In addition, the hydroxyl group coupled with the Ni/Ni ₃ C heterostructure further lowers the water dissociation energy by polarization effects. As a direct outcome, hydroxyl-rich catalysts surpass Pt/C activity at high current density (500 mA cm ^-2 @ ≈276 mV) in alkaline medium.
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