A Cr-doped NiFeOOH catalyst with surface reconfiguration for chloride-resistant simulated seawater electrolysis in an anion-exchange membrane electrolyzer

Abstract

Efficient seawater electrolysis has become one of the promising strategies for sustainable hydrogen production, while the oxygen evolution reaction (OER) in chloride-rich environments is hindered by slow kinetics and the competitive chlorine evolution reaction (ClER). This study presents a chromium-doped Ni–Fe oxyhydroxide catalyst (Cr_xNi-FeOOH/NF) synthesized via a two-step hydrothermal method, enabling enhanced OER activity and chloride resistance. The optimized Cr_MNi-FeOOH/NF catalyst achieves a low overpotential of 230 mV at 100 mA cm⁻² with a competitive Tafel slope of 57.1 mV dec⁻¹, reflecting accelerated reaction kinetics due to Cr³⁺-induced electronic modulation. Cr doping optimizes oxygen intermediate adsorption and forms a hydroxyl-rich surface to repel Cl⁻, suppressing chlorine evolution by >99.7%. While chromium leaching from the catalyst surface was observed during long-term operation, the optimized Cr_MNi-FeOOH/NF exhibited less than 3% activity loss over 100 hours under high Cl⁻ conditions, highlighting the initial efficacy of Cr in enhancing OER kinetics and chloride resistance. Furthermore, the catalyst demonstrated robust performance in an anion-exchange membrane electrolyzer, maintaining stable operation at 200 mA cm⁻² for over 40 hours. This work bridges material design and device validation, offering a scalable strategy for durable simulated seawater electrolysis to advance sustainable hydrogen production.