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

Realizing efficient electrocatalysts is a stepping stone toward achieving high-performance alkaline water/seawater electrolysis, but remains a crucial challenge. Herein, heterogeneous Mo2N/Ni3Mo3N 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 H2O adsorption and OH dissociation processes on the MN-NMN surfaces. Theoretical analysis further confirms that rapid H2O adsorption-dissociation kinetics and H adsorption-conversion kinetics on the Ni3Mo3N/NiOOH and Ni3Mo3N/MoOx 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.