Carbon-Supported Cobalt–Nickel Phosphide as a High-Performance Electrocatalyst for the Efficient Overall Water Splitting

The need for sustainable energy has driven the development of low-cost electrocatalysts for water splitting, which is a key step in the production of hydrogen. Herein, we report a bifunctional carbon-supported cobalt–nickel phosphide catalyst, which has shown excellent catalytic performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), making it a promising candidate for renewable energy technology. The synthesis involves the controlled heating of cobalt, nickel, and phosphorus precursors in the presence of citric acid in a tubular furnace under a nitrogen atmosphere. The resultant carbon-supported cobalt–nickel phosphide (Co–Ni 5 P 4 /C) exhibits excellent functionalities as an electrocatalyst toward HER and OER with low overpotentials of 95 and 153 mV at 10 mA cm –2, respectively, in 1 M KOH alkaline electrolyte. The synergy between cobalt and nickel in the phosphide phase, coupled with the conducting carbon support, enhanced electron transfer kinetics and promoted efficient water splitting. The bifunctional Co–Ni 5 P 4 /C requires a small voltage of 1.8 V at 50 mA cm –2 for the overall splitting of water. Carbon-supported cobalt–nickel phosphide holds significant promise for advancing renewable hydrogen production technology, offering a pathway toward sustainable and clean energy solutions.