Integrated NiOOH@CoMnS hierarchical nanostructured electrocatalyst for sustainable hydrogen conversion via alkaline seawater electrolysis: Synergistic design and Mechanistic insights

Abstract

Alkaline seawater electrolysis would constitute a green pathway to the concurrent production of hydrogen; achieving highly active selective, stable, and reliable electrocatalysts continues to be a challenge. Regarding the imperative of seawater electrolysis, we introduce a well-addressed interconnected hybrid-phase nanosheet framework, hierarchical nanostructured NiOOH@CoMnS electrocatalyst, synthesized through a sequential hydrothermal-electrochemical method that can efficiently catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. The favorable synergistic electron transfer and surface adsorption properties of the heterostructure result in a very low overpotential of 209 mV for OER and 142 mV for HER at 100 mA cm-2. Compared to traditional mono- and bi-metallic catalysts, the NiOOH@CoMnS catalyst exhibits superior electrochemical longevity up to 250 h at both 50 and 200 mA cm-2. Our results show that the catalyst achieves benchmark current densities of 100 and 500 mA cm⁻2 at low potentials (1.50 V and 1.73 V in alkalized seawater; 1.66 V and 1.91 V in 1.0 M KOH), confirming its efficiency for alkaline seawater electrolysis. The results address key challenges like material deactivation and chloride attack, demonstrating that NiOOH@CoMnS is a durable and efficient catalyst for seawater-based hydrogen production. Therefore, this combined electrocatalytic method characterizes sustainable development over conventional water electrolysis for a green hydrogen pathway that could be both economically and environmentally advantageous.