| Summary: | NiFe<sub>2</sub>O<sub>4</sub> material is grown on carbon paper (CP) with the hydrothermal method for use as electrocatalysts in an alkaline electrolyzer. NiFe<sub>2</sub>O<sub>4</sub> material is used as the anode and cathode catalysts (named NiFe(+)/NiFe(−) hereafter). The results are compared with those obtained using CP/NiFe as the anode and CP/Ru as the cathode (named NiFe)(+)/Ru(−) hereafter). During cell operation with NiFe(+)/Ru(−), the current density reaches 500 mA/cm<sup>2</sup> at a cell voltage of 1.79 V, with a specific energy consumption of 4.9 kWh/m<sup>3</sup> and an energy efficiency of 66.2%. In comparison, for NiFe(+)/NiFe(−), the current density reaches 500 mA/cm<sup>2</sup> at a cell voltage of 2.23 V, with a specific energy consumption of 5.7 kWh/m<sup>3</sup> and an energy efficiency of 56.6%. The Faradaic efficiency is 96–99%. With the current density fixed at 400 mA/cm<sup>2</sup>, after performing a test for 150 h, the cell voltage with NiFe(+)/Ru(−) increases by 0.167 V, whereas that with NiFe(+)/NiFe(−) decreases by only 0.010 V. Good, long-term stability is demonstrated.
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