Developing cost-effective electrocatalysts for efficient water splitting is crucial for sustainable hydrogen production. This research reports the synthesis of nanostructured Ni–Cu electrodes via electrochemical deposition followed by selective dealloying. The dealloying process produced a unique coral-like morphology, greatly enhancing the electrochemically active surface area. Interestingly, the optimal deposition current densitydiffered for the two half-reactions: the sample deposited at 50 mA cm-2 showed superior HER activity (η10 = 57 mV, Tafel slope = 65 mV.dec-1), while the 100 mA cm-2 sample demonstrated the best OER performance (η10 = 259 mV, Tafel slope = 55.5 mV.dec-1). A two-electrode configuration using the optimized samples required only 1.55 V to deliver 10 mA cm-2, outperforming many reported Ni-based dealloyed systems. These results highlight that tuning the electrodeposition current density provides a simple yet powerful strategy to tailor bifunctional Ni–Cu electrocatalysts for overall water splitting. Beyond performance optimization, this work provides mechanistic clarification of the unexpected selective dissolution of Cu during dealloying. Although Cu is more noble than Ni, this work shows that the formation of a protective passivation layer of Ni suppresses Ni dissolution, thereby promoting preferential Cu removal and leaving behind a Ni-rich porous framework.

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