Synthesis of non-noble NiMoO4–Ni(OH)2/NF bifunctional electrocatalyst and its application in water-urea electrolysis

Electrochemical water splitting to produce hydrogen is one of the most important technologies for energy storage and conversion. Urea oxidation reaction (UOR) with a lower electrode potential instead of oxygen evolution reaction (OER, water-splitting anode) in the water-urea electrolysis is an energy-saving approach. In this paper, NiMoO4–Ni(OH)2/NF is synthesized by hydrothermal reactions and explored as both hydrogen evolution reaction (HER) and UOR catalyst electrodes. This composite catalyst shows high catalytic bifunctional activities towards both HER and UOR. To validate both catalytic UOR and HER activities and durability, a two-electrode water-urea electrolyzer composed of NiMoO4–Ni(OH)2/NF as both anode and cathode materials is constructed (NiMoO4–Ni(OH)2/NF||NiMoO4–Ni(OH)2). Experiments show that a voltage of 1.341 V with a high stability (over 3000 CV cycles) can be achieved at 10 mA cm−2, which are much better than those obtained using a Pt/C||IrO2.