Pulsed-Potential Stabilization of Cobalt-Based Oxygen Evolution Catalysts in Trace Iron-Containing Alkaline Electrolyte

Cobalt-based oxyhydroxides are promising oxygen evolution reaction catalysts in alkaline media, but their catalytic performance is strongly affected by dynamic surface reconstruction and iron dissolution or redistribution during operation. In this study, we investigate how trace iron in the electrolyte and pulsed-potential operation can be combined to stabilize Co-derived OER catalysts under alkaline conditions. Co foil electrodes were electrochemically converted into Co(Fe)OxHy in 0.1 M KOH containing 0.1 ppm Fe, and pulsed-potential protocols were applied by alternating OER operation at 1.65 V vs. RHE with short pulses at selected lower potentials. Among the tested conditions, repeated OER operation at 1.65 V vs. RHE for 1 h followed by pulsing at 1.45 V vs. RHE for 1 min showed the highest stability. Electrochemical impedance spectroscopy and double-layer capacitance analysis revealed that pulsed operation suppresses the increase in charge-transfer resistance and maintains electrochemically accessible surface area compared with constant-potential operation. Control experiments further indicate that both trace Fe in the electrolyte and continuous pulsing are required to sustain the enhanced stability. These results suggest that pulsed-potential operation dynamically regulates the Co(Fe)OxHy surface, likely by promoting reversible surface reconstruction and Fe redeposition during the pulse step. This work provides a simple operational strategy for improving the stability of Co-based OER catalysts through electrolyte and potential-program control.