Despite the long-standing recognition of nickel as an effective electrocatalyst for the alkaline hydrogen evolution reaction (HER), the majority of extant studies primarily focus on initial catalytic performance or short-term stability under relatively low current densities. In practical alkaline water electrolysis, however, electrodes operate continuously at elevated current densities for extended periods, where surface chemical states and electrochemical responses may evolve dynamically. A systematic understanding of such time-dependent behaviour remains limited, particularly for electrodeposited nickel under sustained operation. In this study, the long-term HER performance of electrodeposited Ni electrodes at a current density of 100 mA cm−2 over 120 h is investigated. The objective of this study is to correlate the evolution of electrochemical performance with changes in surface chemical states during prolonged electrolysis. To this end, a combination of methods was employed, including polarization measurements, electrochemical impedance analysis, double-layer capacitance evaluation, and ex situ surface characterization. In contrast to the tendency to prioritize absolute enhancement of activity, this study places greater emphasis on the transient decline–recovery–stabilization behaviour that is observed during operation. Furthermore, it discusses the potential relationship of this behaviour with surface hydroxylation and restructuring processes. The present study utilizes a time-resolved analysis to elucidate the dynamic surface evolution of nickel electrodes under practical alkaline HER conditions, thereby underscoring the significance of evaluating catalyst durability beyond the confines of short-term measurements. The findings presented herein contribute to a more realistic assessment of nickel-based electrodes for alkaline water electrolysis applications.
Yao et al. (Fri,) studied this question.