The advancement of direct seawater electrolysis is a significant step towards sustainable hydrogen production, addressing the critical need for renewable energy sources and efficient resource utilization. However, direct seawater electrolysis has to face several challenges posed by the corrosiveness of highly concentrated chloride and the competitive chlorine evolution reaction (ClER). To overcome these issues, we designed a novel NiP₂@CoP electrocatalyst on a porous titanium microfiltration (Ti MF) membrane. The obtained bifunctional NiP₂@CoP catalyst outperforms the Pt/C and IrO₂, as evidenced by its low overpotentials of 192 and 425 mV at a current density of 500 mA·cm⁻² for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline seawater (1 M KOH + 0.5 M NaCl), respectively. Especially, only 231 and 569 mV overpotentials are required at the current density of 1500 mA·cm⁻² towards HER and OER in alkaline seawater, respectively. More importantly, no ClER was observed, demonstrating its excellent selectivity to OER. The selection of porous Ti MF membrane as an electrode substrate further enhances the performance by providing a robust structure that promotes the fast generation and release of gas bubbles. Our promising outcomes obtained with NiP₂@CoP catalysts on Ti MF support, therefore, pave the way for the commercial viability of direct seawater electrolysis technologies at industrial-level current densities.

The activity and durability of electrocatalysts are important factors in their practical applications, such as electrocatalytic oxygen evolution reactions (OERs) used in water splitting cells and metal–air batteries. In this study, a novel electrocatalyst, comprising few-layered graphitic carbon (~5 atomic layers) encapsulated heazlewoodite (Ni₃S₂@C) nanoparticles (NPs), was designed and synthesized using a one-step solid phase pyrolysis method. In the OER test, the Ni₃S₂@C catalyst exhibited an overpotential of 298 mV at a current density of 10 mA·cm^–2, a Tafel slope of 51.3 mV·dec^–1, and charge transfer resistance of 22.0 Ω, which were better than those of benchmark RuO₂ and most nickel-sulfide-based catalysts previously reported. This improved performance was ascribed to the high electronic conductivity of the graphitic carbon encapsulating layers. Moreover, the encapsulation of graphitic carbon layers provided superb stability without noticeable oxidation or depletion of Ni₃S₂ NPs within the nanocomposite. Therefore, the strategy introduced in this work can benefit the development of highly stable metal sulfide electrocatalysts for energy conversion and storage applications, without sacrificing electrocatalytic activity.