The sluggish kinetics of water oxidation has severely hindered the energetic convenience of electrochemical water splitting. In this work, we describe our recent finding that NiS₂ nanosheet array on Ti mesh (NiS₂/TiM) is a superior catalyst for hydrazine oxidation reaction (HzOR) with the demand of potential of 218 mV to drive 300 mA cm⁻² in 1.0 M KOH with 0.5 M hydrazine. Interestingly, its high activity toward hydrogen evolution reaction enables it as a bifunctional catalyst for energy-efficient electrolytic hydrogen generation, and the two-electrode alkaline electrolyzer using NiS₂/TiM as both anode for HzOR and cathode for HER needs a cell voltage of only 0.59 V to attain 50 mA cm⁻², 1.34 V less compared with pure water splitting to achieve the same current density, promising the use of such 3D catalyst electrode toward energy-saving electrochemical production of hydrogen fuels.