Dynamic ferrous iron regeneration enables stabilization of NiFeCo layered double hydroxide for enhanced alkaline water oxidation

Nickel–iron layered double hydroxides (NiFe LDH) are cost-effective and high-performance electrocatalysts for the oxygen evolution reaction (OER) comparable to noble metals. However, their stability is hindered by Fe leaching under oxidative alkaline conditions, resulting in catalyst deactivation . This work proposes to address the limited stability of NiFe LDH by introducing cobalt doping and Fe 2+ ions into the electrolyte. Cobalt enhances the catalytic activity and facilitates the oxidation of Fe 2+ to Fe 3+ to replenish the Fe active sites lost during OER. Electrochemical tests demonstrate that NiFeCo LDH achieves a lower overpotential of 209 mV at 10 mA cm −2 and improved kinetics (Tafel slope of 86 mV dec −1 ) compared to NiFe LDH (287 mV at 10 mA cm −2 , Tafel slope of 170 mV dec −1 ). Stability test shows NiFeCo LDH maintains activity for over 120 h with 0.1 mM Fe 2+ , whereas NiFe LDH deactivates after 35 h. ICP-OES confirms stable Fe concentrations in NiFeCo LDH with Fe 2+ addition, unlike in NiFe LDH where Fe concentration decreases over long-term operation. This approach of Fe regeneration via cobalt-catalyzed oxidation extends the lifetime of NiFeCo LDH in alkaline electrolysis up to 120 h enhancing the stability of NiFe-based OER catalysts for long-term applications. • Cobalt doping improves NiFe LDH activity and reduces overpotential. • Fe 2+ regeneration restores iron, enhancing catalyst stability in OER. • NiFeCo LDH achieves 120-h stability with Fe 2+ addition. • Controlled Fe redeposition minimizes leaching, extending catalyst lifetime. • High current densities accelerate Fe loss, requiring further optimization.