Dual-ion engineering of Fe-doped Ni₃(OH)₄(NO₃)₂ for Cl⁻-resistant oxygen evolution reaction in alkaline medium

Seawater electrolysis offers a sustainable pathway for green hydrogen production, yet the development of oxygen evolution reaction (OER) catalysts with robust Cl¯ resistance remains a critical challenge. Here, we propose a dual-ion modification strategy, incorporating NO₃¯ and Fe³⁺ cations into Ni(OH)₂ (denoted as Fe-NiNH/NF), to synergistically enhance Cl¯ resistance and OER activity in alkaline simulated seawater. The Fe-NiNH/NF catalyst demonstrates exceptional performance, requiring only 320 mV overpotential at 100 mA cm⁻² in KOH and NaCl solution, with a negligible 10 mV increase compared to pure KOH. When implemented in an alkaline anion exchange membrane water electrolyzer, the catalyst achieves 1.76 V cell voltage at 1 A cm⁻² with 350-h stability. Post-reaction characterizations confirm the transformation of Fe-NiNH/NF into Fe-NiOOH with adsorbed NO₃¯. Theoretical calculations reveal that NO₃¯ forms an exclusionary layer via strong polarity and steric hindrance, electrostatically repelling Cl¯, and NO₃¯ and Fe³⁺ collectively downshift the Ni d-band center, weakening Cl¯ adsorption while optimizing intermediate binding.