Electronically coupled Co single atoms with Co-Pd alloy catalyst for high-performance rechargeable hydrazine-assisted...

Zinc-air batteries are promising devices for use in safe and cost-effective energy storage applications. However, their practical utility is hindered by sluggish oxygen evolution and oxygen reduction reactions. We show that hybridizing electronically coupled Co single atoms and a CoPd alloy within a three-dimensional macroporous N-doped carbon (CoPd/Co@3D NC) enables high-performance N₂H₄-assisted zinc-air batteries, where the oxygen evolution reaction is replaced with the thermodynamically more favorable hydrazine oxidation reaction. Experimental and theoretical data reveal that electronic coupling between the Co single atoms and the CoPd alloy mutually modifies their electronic structures, which, in turn, weakens oxygen adsorption on the Co single atoms and enhances N₂H₄ adsorption on the Pd sites. The electronic-coupling effect accelerates the rate-limiting steps of the oxygen evolution and hydrazine oxidation reactions. Consequently, N₂H₄-assisted zinc-air batteries employing CoPd/Co@3D NC exhibit a small charging/discharging voltage gap of 0.52 V at 100 mA cm^-2, a peak specific power of 151 mW cm^-2, and a specific capacity of 810 mAh g^-1 at 10 mA cm^-2; these values are competitive when compared to those exhibited by conventional zinc-air batteries.