Synergistic Interactions in Nanostructured CuNi ₂ Bimetallic Alloy for Superior Hydrogen Evolution Reaction Kinetics and Stability

Green hydrogen represents a highly promising renewable energy resource, and its production through water electrolysis relies on the hydrogen evolution reaction (HER). In this study, we synthesized a low-cost, transition metal-based electrocatalyst, CuNi 2 alloy (CNA), via a solvothermal method to generate hydrogen through alkaline water electrolysis. The nanocrystalline, coin-shaped CNA particles displayed a uniform elemental distribution across the catalyst surface. The electrocatalyst exhibited outstanding HER activity and long-term operational stability. Electrochemical measurements performed in a three-electrode configuration with 1.0 M KOH solution yielded overpotentials of 40 ± 2 mV and 152 ± 5 mV at geometric current densities of 10 and 50 mA cm –2, respectively, confirming its high electrocatalytic HER performance. The HER kinetics, characterized by a Tafel slope of 71.7 mV dec –1, indicated that the hydrogen evolution proceeded via the Volmer–Heyrovsky mechanism. Compared with a reference NiO catalyst supported on nickel foam, CNA delivered significantly superior activity, emphasizing the synergistic effect of its bimetallic composition. Further evaluation in a two-electrode water electrolyzer, employing platinum black as the anode catalyst, revealed that the system required a cell voltage of −1.73 V to achieve a current density of −10 mA cm –2 . The cell maintained stable electrochemical performance with negligible degradation during a 12 h chronoamperometric test and under stepwise chronoamperometry at varying applied potentials. Post-electrolysis spectroscopic and morphological analyses verified that the catalyst phase remained intact after prolonged operation. This work establishes a cost-effective strategy for synthesizing CNA, elucidates its HER mechanism, and validates its durability and efficiency for practical electrolyzer applications.