Interface Engineering of Ni ₃ S ₂ @CoFe‐P Core‐Shell Enhances Alkaline Seawater Hydrogen Evolution Reaction

Abstract Owing to the abundance of seawater, hydrogen production via direct seawater electrolysis is a promising technology for sustainable energy production. However, the construction of efficient and durable catalysts and their application in seawater electrolysis remains a considerable challenge. Here, the precursor of NiFe‐based Prussian blue analogs (NiFe PBA) was synthesized in situ on a corrosion‐resistant nickel sulfide substrate, followed by phosphating to successfully preparing a core‐shell transition metal phosphide/sulfide (Ni 3 S 2 @CoFe‐P) catalyst. The prepared Ni 3 S 2 @CoFe‐P catalyst obtained overpotentials of 75 and 153 mV in alkaline (1 M KOH) and alkaline seawater (1 M KOH + seawater) at 10 mA cm −2 for hydrogen evolution reaction (HER), respectively. The excellent HER performance of the catalyst is attributed to the synergistic effect between the heterogeneous interfaces of Ni 3 S 2 @CoFe‐P, which can effectively optimize the electronic structure of the electrocatalyst and accelerate the electron transfer. Meanwhile, the core‐shell structure exposes abundant active sites. In addition, the Ni 3 S 2 @CoFe‐P catalyst was able to operate smoothly in seawater for 100 h due to the inherent corrosion resistance of metal phosphides. This work offers a viable approach to design high‐performance bifunctional catalysts for seawater splitting.