Competitive Optimization of Interfacial Water Dissociation and Hydroxyl Reductive Desorption of MoCoNi‐Based Catalysts for Superior Alkaline Hydrogen Evolution

Nano-heterointerface serves as a catalytic center for water dissociation promoted by the concerted interaction of *OH on oxide and *H on nitride. Kinetic energetics of water dissociation and hydroxyl (de)stabilization are vital to surface coverage of reactive *H and surface charge for *OH reductive desorption. electron paramagnetic resonance spectra of DMPO-H and DMPO-OH unravel radical nature of water-dissociated *H and *OH. coherent synergism of interfacial ensemble and electronic effects realizes TOF/η <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mn>10</mml:mn> <mml:mspace></mml:mspace> <mml:mi>mA</mml:mi> <mml:mspace></mml:mspace> <mml:msup><mml:mi>cm</mml:mi> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>2</mml:mn></mml:mrow> </mml:msup> </mml:mrow> </mml:msub> <mml:annotation>$ {_{\rm 10\, mA\, cm^{-2}}} $</mml:annotation></mml:semantics> </mml:math> -ɛ_d volcano as the net result of work-function-directed competition between interfacial water dissociation (covalent control) and *OH reductive desorption (ionic control) kinetics, manifesting that alkaline HER volcano shaped by d-band descriptor originates from intricate balance guided by work function descriptor. Orchestrated with alkali metal cations on fine-tuning covalent/ionic interaction between catalyst surface and water-derived intermediates, microrod-array N-MoCoNiAl/NF electrode (NF═Ni foam) drives 10 mA cm^-2 at overpotential of 10 mV in 1 m KOH. The proposed pathway may provide insight into how the peculiar electronic structure of multi-site heterojunction and the interfacial hard-soft covalent/electrostatic interactions impact molecular-level mechanism for efficient Volmer kinetics.