Replacing Oxygen Evolution with Hydrazine Oxidation at the Anode for Energy‐Saving Electrolytic Hydrogen Production

We report the development of a cobalt phosphide nanoarray as an efficient and stable catalyst for the hydrazine oxidation reaction (HzOR) in alkaline media. Its high hydrogen evolution reaction (HER) activity enables it to be used as a bifunctional catalyst for less energy‐intensive electrolytic hydrogen generation by replacing the sluggish oxygen evolution reaction with HzOR. The corresponding two‐electrode electrolyzer using such a nanoarray as both the anode for HzOR and the cathode for HER only needs a cell voltage of 0.2 V to drive 10 mA cm −2 in 1.0 M KOH with 100 mM hydrazine, which is 1.45 V less than that for pure water splitting. This electrolyzer also shows strong long‐term electrochemical durability with nearly 100 % faradic efficiency for hydrogen evolution.