Self-supported FexNi1-xMoO4 with synergistic morphology and composition for efficient overall water splitting at large current density

Developing the high activity, low cost and robust large-current-density-based electrocatalysts is of great significance for the industrial electrolytic water splitting. However, the current range of most reported materials is small, which makes it difficult for them to play their roles in practical applications. Here, a self-supported amorphous Fe_xNi_1-xMoO₄/IF treated with ammonium fluoride (AF_0.1-FNMO/IF) is synthesized by one-step hydrothermal method. With the help of NH₄F, AF_0.1-FNMO/IF exhibits a vertically cross-linked nanosheet with spherical structure. Electrochemical measurement shows that AF_0.1-FNMO/IF affords a large current density ordeal and only need low overpotentials of 289 and 345 mV to reach a current response of 500 mA/cm² for oxygen evolution reaction and hydrogen evolution reaction, respectively, together with long-time stability (both at 500, 1000 and 2000 mA/cm²) in 1.0 mol/L KOH solution. Using it as bifunctional catalyst for overall water splitting, the current densities of 100, 500, 1000 and 1500 mA/cm² are achieved at a cell voltage of 1.71, 1.88, 1.94 and 1.97 V with excellent durability, which is much better than that of most published electrodes. The work provides valuable insight for designing higher activity nickel iron-based molybdate catalysts with large current density.