Self‐Activated CuAg Metal Heterojunctions for Hydrazine‐Assisted Hydrogen Evolution and Zn–Hz Battery Applications

Harnessing hydrazine-assisted reactions in advanced energy devices presents a promising approach for energy-efficient hydrogen production and next-generation batteries. We present a CuAg/NCF catalyst, supported on porous NiCo foam, that effectively drives both the hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). The Cu-Ag interfacial interaction enhances the active sites, while the 3D nanoneedle structure improves surface area and mass transport. In alkaline conditions, CuAg/NCF achieves industrial-level HER current densities of 500 and 1000 mA cm-2 at overpotentials of 306 and 340 mV. For HzOR, it attains 100 mA cm-2 at -113 mV, while 500 and 1000 mA cm-2 are achieved at -9.7 and 53 mV, respectively, with a low Tafel slope of 34.45 mV dec-1. The overlapping potential window (∼0.19 V) allows a hydrazine-assisted water-splitting electrolyzer to reach 1000 mA cm-2 at just 0.477 V, saving 85% of the energy compared to traditional water splitting, with excellent 48-h stability and nearly 100% Faradaic efficiency. Leveraging this performance, a zinc-hydrazine (Zn-Hz) battery using CuAg/NCF as the cathode achieves over 93% energy efficiency and a peak power density of 1.74 mW cm-2. This work highlights Cu-Ag heterojunction synergy in boosting HER and HzOR, enabling energy-efficient hydrazine-assisted water splitting and high-performance Zn-Hz batteries.