Statistically Guided Electrodeposition of NiFe Electrocatalysts for Alkaline Oxygen Evolution Reaction

Abstract

Scalable control of NiFe electrodeposition is essential for developing efficient alkaline oxygen evolution reaction (OER) electrodes. Here, response surface methodology coupled with a rotatable central composite design was used to simultaneously quantify the effects of deposition current density, deposition temperature, and bath Ni2+/Fe2+ molar ratio on the overpotential at 10 mA cm–2 (η10) and Tafel slope. Bath composition and deposition temperature were the dominant factors, whereas deposition current density was not statistically significant for η10 within the investigated low-current-density range. Multiresponse optimization identified 8.58 mA cm–2, 39 °C, and a bath Ni2+/Fe2+ molar ratio of 1.88 as the optimum deposition conditions. Experimental validation using independently prepared electrodes yielded η10 = 235 mV and a Tafel slope of 69 mV dec–1 in 1 M KOH. The validated electrode consisted predominantly of γ-(Ni,Fe) with a bulk composition of Ni53.6Fe46.4. Electrochemical impedance analysis revealed a regime-dependent relationship between charge-transfer resistance and Tafel behavior, indicating coupled contributions of interfacial charge transfer and surface kinetics to the observed OER performance. The electrode retained 70.9% of its initial anodic response after 1000 cycles and sustained chronopotentiometric operation for 70 h at 10 mA cm–2. After the stronger early stage potential evolution, the 20–70 h interval showed a net increase of 3.3 mV, corresponding to a drift rate of 0.066 mV h–1. Post-OER FESEM showed retained lamellar regions together with localized morphological reorganization, while AAS of the unfiltered post-test electrolyte detected total Fe and Ni concentrations of 1.82 and 1.42 mg/L, respectively. These results demonstrate that the statistically optimized NiFe electrode combines favorable laboratory-scale OER performance with sustained long-term electrochemical operation, while post-test characterization reveals measurable material evolution during extended anodic polarization. Overall, this study establishes a statistically validated framework for linking multivariable NiFe electrodeposition conditions with precursor characteristics and laboratory-scale OER performance.