High‐Performance Alkaline Freshwater and Seawater Hydrogen Catalysis by Sword‐Head Structured Mo2N‐Ni3Mo3N Tunable Interstitial Compound Electrocatalysts

Abstract Realizing efficient electrocatalysts is a stepping stone toward achieving high‐performance alkaline water/seawater electrolysis, but remains a crucial challenge. Herein, heterogeneous Mo 2 N/Ni 3 Mo 3 N electrocatalysts on nickel foam (denoted MN‐NMN/NF) that is stable and active for the hydrogen evolution reaction (HER) in both alkaline water/seawater are demonstrated. The optimized MN‐NMN09/NF achieves an ultralow HER overpotential of 11 mV@10 mA cm −2 in 1.0 m KOH electrolyte, which is not only superior to the benchmark Pt/C catalysts but also the best reported ever among NiMo‐based electrocatalysts in an alkaline environment. Successively, the optimized MN‐NMN09/NF electrocatalyst can drive HER current densities of 10 and 500 mA cm −2 using low overpotentials of 9.37 and 123 mV in 1.0 m KOH seawater electrolyte, which remains durable after 120 h long‐term electrolysis at a constant current density of 500 mA cm −2 . In situ Raman analysis reveals that the enhanced performance is attributed to the accelerated H 2 O adsorption and OH dissociation processes on the MN‐NMN surfaces. Theoretical analysis further confirms that rapid H 2 O adsorption‐dissociation kinetics and H adsorption‐conversion kinetics on the Ni 3 Mo 3 N/NiOOH and Ni 3 Mo 3 N/MoO x surfaces result in boosted HER capability. This work depicts a significant potential for designing stable and efficient hydrogen production electrocatalysts for both alkaline water and seawater electrolysis.