Three-dimensional lily-like CoNi2S4 as an advanced bifunctional electrocatalyst for hydrogen and oxygen evolution reaction

Designing low-cost, highly efficient, and stable bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of vital significance for water splitting. Herein, three-dimensional lily-like CoNi 2 S 4 supported on nickel foam (CoNi 2 S 4 /Ni) has been fabricated by sulfuration of the Co–Ni precursor. As expected, CoNi 2 S 4 /Ni possesses such outstanding electrocatalytic properties that it requires an overpotential of only 54 mV at 10 mA cm −2 and 328 mV at 100 mA cm −2 for HER and OER, respectively. Furthermore, by utilizing the CoNi 2 S 4 /Ni electrodes as bifunctional electrocatalysts for overall water splitting, a current density of 10 mA cm −2 can be obtained at a voltage of only 1.56 V.