Rational Design of FeCo-S/Ni₂P/NF Heterojunction as a Robust Electrocatalyst for Water Splitting

The rational design of nonnoble-metal-based catalysts with high electroactivity and long-term stability, featuring controllable active sites, remains a significant challenge for achieving effective water electrolysis. Herein, a heterogeneous catalyst with a FeCo-S and Ni₂P heterostructure (denoted FeCo-S/Ni₂P/NF) grown on nickel foam (NF) was synthesized by a solvothermal method and low-temperature phosphorization. The FeCo-S/Ni₂P/NF catalyst shows excellent electrocatalytic performance and stability in alkaline solution. The FeCo-S/Ni₂P/NF catalyst demonstrates low overpotentials (η) for both the hydrogen evolution reaction (HER) (49 mV@10 mA cm^-2) and the oxygen evolution reaction (OER) (279 mV@100 mA cm^-2). Assembling the FeCo-S/Ni₂P/NF catalyst as both cathode and anode in an electrolytic cell for overall water splitting (OWS) needs an ultralow cell voltage of 1.57 V to attain a current density (CD) of 300 mA cm^-2. Furthermore, it demonstrates excellent durability, significantly outperforming the commercial Pt/C∥IrO₂ system. The results of experiments indicate that the heterostructure and synergistic effect of FeCo-S and Ni₂P can significantly enhance conductivity, facilitate mass/ion transport and gas evolution, and expose more active sites, thereby improving the catalytic activity of the electrocatalyst for the OWS. This study provides a rational approach for the development of commercially promising dual-functional electrocatalysts.