Bifunctional Copper-Doped Nickel Catalysts Enable Energy-Efficient Hydrogen Production via Hydrazine Oxidation and Hydrogen Evolution Reduction

Hindered by sluggish kinetics and large overvoltages of direct hydrazine oxidation, energy-efficient electrolytic hydrogen generation from whole cell hydrazine electrolysis still remains a great challenge. Herein, we present a 3D hierarchically nanotubular Ni–Cu alloy on nickel foam (Ni(Cu)/NF) and demonstrate its high efficiency and strong durability for the hydrazine oxidation reaction (HzOR) with a required potential of merely 86 mV to afford a current density of 100 mA cm–2 in alkaline hydrazine aqueous solution. The normalization of HzOR polarization curves for Ni(Cu)/NF manifests that the superlarge electrochemical active surface area (ECSA) with an 18-fold increase is the main contributor to the excellent HzOR performance. The superior cell performance makes Ni(Cu)/NF a good alternative transition-metal-based electrocatalyst for utilization in the HzOR electrolyzer. The remarkable performance toward the hydrogen evolution reaction (HER) of Ni(Cu)/NF allows the use of a superior bifunctional electrocatalyst for electrolytic hydrogen production via HzOR and HER. In a two-electrode electrolyzer cell employing Ni(Cu)/NF to function as the cathode and anode, an extremely low cell voltage of 0.41 V is required to afford 100 mA cm–2 with remarkable long-term stability.