Nanoengineered, Mo-Doped, Ni3S2 Electrocatalyst with Increased Ni–S Coordination for Oxygen Evolution in Alkaline Seawater

Electrochemical seawater splitting using efficient HER (hydrogen evolution reaction) and OER (oxygen evolution reaction) electrocatalysts have become an appropriate method for the mass production of green hydrogen. In this study, a noble-metal free OER electrocatalyst consisting of Mo-doped Ni3S2 nanocluster arrays on Nickle foam (Mo–Ni3S2/NF)─fabricated using a modified one-step solvothermal approach─is developed and evaluated. The proposed electrocatalyst demonstrates exceptional OER activity, requiring overpotentials of only 212 and 291 mV to deliver OER current densities of 10 and 100 mA cm–2, respectively, in alkaline seawater. The presence of Mo promotes Ni–S coordination, resulting in strong electronic interactions and substantially enhanced OER kinetics. Meanwhile, surface sulfate ions and (oxy)hydroxide (NiOOH) generated during the OER lead to enhanced activity and corrosion resistance, enabling Mo–Ni3S2/NF to operate continuously at 100 mA cm–2 for 500 h in alkaline natural seawater. This study is expected to inform the progression of sulfur-based transition-metal electrocatalysts for seawater oxidation.