UC Berkeley

We report the effect of reverse polarization on thin-film Ni(Fe)OOH anodes in conditions that mirror those seen in commercial alkaline water electrolyzer stacks. Regardless of the extent of the reverse polarization potential, the anodic charge capacity decreases over successive cycles, indicating loss of active Ni2+/Ni3+ sites. Electrodes held for a longer period in the reduced state exhibited an accelerated catalyst loss through dissolution and structural reorganization during reverse polarization. In situ Raman spectroscopy and X-ray photoelectron spectroscopy revealed a significant decrease in the Fe:Ni surface ratio after reverse polarization, which correlates with a measurable decline in activity toward the oxygen evolution reaction. These findings illustrate how nickel iron oxyhydroxide anodes degrade during reverse polarization conditions and how managing the dissolved ions in the recirculating KOH improves anode lifetimes.