Robust Fe, Mo co-doped Co3O4 electrocatalyst with superior chloride resistance for efficient seawater electrolysis

Abstract Hydrogen production via seawater electrolysis represents a promising strategy for sustainable energy conversion. However, its practical deployment remains limited due to catalyst corrosion and performance degradation induced by chloride ions. Herein, we report the facile synthesis of a ternary Fe-Mo-Co oxide (Fe-CMO) electrocatalyst designed for efficient overall seawater splitting. The Fe-CMO catalyst was grown on Ni foam via a two-step hydrothermal process followed by annealing under an Ar/H 2 atmosphere, yielding a nanoflower-like architecture composed of uniformly distributed Mo 4+ /Mo 6+ , Co 2+ /Co 3+ , and Fe 2+ /Fe 3+ redox couples. In this system, Mo 6+ facilitates oxygen evolution reaction (OER) by regenerating Co-based active sites, while Mo 4+ enhances hydrogen evolution reaction (HER) through its electron-reservoir characteristics. The incorporation of Fe further modulates the electronic structure of Co, improving the adsorption of reaction intermediates. As a result, Fe-CMO exhibits outstanding bifunctional activity, achieving low overpotentials of 288 mV for OER and 50 mV for HER at 50 mA cm⁻ 2 in 1 M KOH. Notably, in the presence of seawater, Fe-CMO maintains excellent performance with overpotentials of 289 mV for OER and 98 mV for HER, along with remarkable stability, showing only a 1.1% performance loss after 120 h at 100 mA cm⁻ 2 . These findings demonstrate the effectiveness of rational multimetal design in constructing durable and efficient electrocatalysts for practical seawater electrolysis.