Partial-sacrificial-template Synthesis of Fe/Ni Phosphides on Ni Foam: A Strongly Stabilized and Efficient Catalyst for Electrochemical Water Splitting

Electrochemical water splitting is considered to be one of the most promising strategies for clean and efficient hydrogen production. In this paper, an in-situ growth of iron-nickel phosphide on nickel foam (FeNiP_x/NF) is demonstrated as a self-supported ternary catalyst for electrochemical water splitting. The FeNiP_x/NF were prepared by a thermo-reaction between NaH₂PO₂ and NiFe hydroxide precursors that are in situ grown on Ni foam via a simple chemical precipitation reaction. In this newly proposed method, the nickel foam not only acts as an electrode substrate, but also serves as a slow-release Ni source in the reaction due to its oxidation by Fe³⁺ in solution. Benefiting from collaborative advantages of bimetallic composite, metallic phosphide, and unique electrode fabrication, the FeNiP_x/NF exhibits extraordinarily high activities for both OER and HER with low overpotentials of of 192 and 106 mV at 10 mA cm⁻², 236 and 161 mV at 100 mA cm⁻², respectively. The voltage during the galvanostatic electrolysis is well maintained for almost 400 h without any visible elevation, representing the few most stable noble-metal-free catalysts for water splitting.