Synthesis of N doped NiZnCu-layered double hydroxides with reduced graphene oxide on nickel foam as versatile electrocatalysts for hydrogen production in hybrid-water electrolysis

Water splitting is limited by the high theoretical potential of oxygen evolution reaction (OER) at anode, which can reduce the energy efficiency. Nevertheless, replacing sluggish oxygen evolution by ammonia oxidation reaction (AOR), urea oxidation reaction (UOR), hydrazine oxidation reaction (HzOR)) of low theoretical potential is an energy-saving approach. In this paper, a new bifunctional catalyst of N doped NiZnCu-layered double hydroxides with reduced graphene oxide on nickel foam (N-NiZnCu LDH/rGO) is synthesized. To validate its electrochemical performance and stability, a two-electrode electrolyzer is constructed (N-NiZnCu LDH/rGO parallel to N-NiZnCu LDH/rGO). Experiments show that at a current density of 10 mA cm(-2), the voltages of AOR, UOR, and HzOR are 0.489 V, 1.305 V, and 0.010 V with a high stability (over 3000 CV cycles), which are much better than those of Pt/C parallel to IrO2. This study demonstrates N-NiZnCu LDH/rGO can replace precious metals for commercial hydrogen energy production in the hybrid-water electrolysis, and can be employed for treatment of industrial wastewater.