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

ABSTRACT 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.