Redox-Durable Co-Ni-Fe Layered Double Hydroxide Anode for Stable Oxygen Evolution under Industrially Relevant Cycling

Designing a highly robust oxygen evolution reaction (OER) electrocatalyst under industrially relevant conditions, especially repeated start-up and shutdown cycling, is crucial to achieving efficient electrolysis when connected to a renewable energy source, such as wind and solar, for mass hydrogen production. This study investigates the degradation mechanisms of finely synthesized NiFe-, CoFe-, and CoNiFe-LDH via operando Raman and operando X-ray absorption spectroscopy and electrochemical analysis. The most active NiFe-LDH degraded severely under repeated on-off cycles versus constant OER operation due to a decrease in the conductivity of the catalyst, suppression of Ni oxidation, and amorphization. CoFe-LDH had the most degraded OER performance among the investigated catalysts under intermittent operation due to the large structural changes and significant Fe dissolution during cycling. In contrast, CoNiFe-LDH exhibited exceptional durability because of its high structural stability and redox robustness arising from its intermediate structural framework and modified electronic interaction with the coexistence of Co and Ni. Co helped Ni to oxidize more easily and contributed to maintaining its redox ability. The CoNiFe-LDH demonstrated noteworthy on-off durability under industrially relevant conditions (600 mA cm^-2, 60 °C), indicating that CoNiFe-LDH is a promising OER electrocatalyst for durable alkaline electrolyzers.