Highly efficient and stable NiFe oxide-based electrocatalysts for oxygen evolution in alkaline and saline solutions
Soumia El Boumlasy, Mariarosaria Pascale, Oreste De Luca, T. Caruso, S. Mirabella, A. Terrasi, A.S. Aricò, F. Ruffino
Abstract
Developing cost-effective and stable oxygen evolution reaction (OER) catalysts is crucial for advancing hydrogen production via water electrolysis. Given the growing scarcity of freshwater resources, seawater electrolysis offers a promising alternative. However, maintaining both high catalytic activity and long-term durability in saline environments remains a significant challenge. In this study, four catalysts, nickel oxide (NiO), two nickel-iron oxides (Ni₀.₈₅Fe₀.₁₅O and Ni₀.₆₅Fe₀.₃₅O), and iron oxide (Fe₂O₃), were synthesized using a simple chemical bath deposition method and systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). Among them, Ni₀.₈₅Fe₀.₁₅O exhibited the best OER performance, achieving a low overpotential of 348 mV at 10 mA cm⁻² and a Tafel slope of 52 mV dec⁻¹ after 24 h of operation in surrogate seawater (1 M KOH + 2.45 wt % NaCl). This superior activity is attributed to its compact nanosheet morphology and the synergistic interaction between Ni²⁺ and Fe³⁺, which induces lattice strain and increases the density of active sites, as confirmed by SEM and XPS. Electrochemical surface area (ECSA) analysis further revealed a high number of accessible and stable active sites under saline conditions, supporting the catalyst’s intrinsic activity. Ni₀.₈₅Fe₀.₁₅O demonstrates OER performance and durability comparable to state-of-the-art seawater electrolysis catalysts, underscoring its potential for scalable and sustainable hydrogen production.