Optimizing Hydrazine Activation on Dual-Site Co-Zn Catalysts for Direct Hydrazine-Hydrogen Peroxide Fuel Cells

Abstract

Direct hydrazine-hydrogen peroxide fuel cells (DHzHPFCs) offer unique advantages for air-independent applications, but their commercialization is impeded by the lack of high-performance and low-cost catalysts. This study reports a novel dual-site Co-Zn catalyst designed to enhance the hydrazine oxidation reaction (HzOR) activity. Density functional theory calculations suggested that incorporating Zn into Co catalysts can weaken the binding strength of the crucial N₂H₃* intermediate, which limits the rate-determining N₂H₃* desorption step. The synthesized p-Co₉Zn₁ catalyst exhibited a remarkably low reaction potential of −0.15 V versus RHE at 10 mA cm⁻², outperforming monometallic Co catalysts. Experimental and computational analyses revealed dual active sites at the Co/ZnO interface, which facilitate N₂H₃* desorption and subsequent N₂H₂* formation. A liquid N₂H₄-H₂O₂ fuel cell with p-Co₉Zn₁ catalyst achieved a high open circuit voltage of 1.916 V and a maximum power density of 195 mW cm⁻², demonstrating the potential application of the dual-site Co-Zn catalyst. This rational design strategy of tuning the N₂H₃* binding energy through bimetallic interactions provides a pathway for developing efficient and economical non-precious metal electrocatalysts for DHzHPFCs.