CoFe2O4@N-CNH as Bifunctional Hybrid Catalysts for Rechargeable Zinc-Air Batteries

Abstract

Improving the efficiency of bifunctional electrocatalysts is a decisive challenge in the area of long-lasting rechargeable zinc-air batteries. Enhancing the catalysts' performance is crucial for advancing zinc-air batteries. Transition-metal oxides have emerged as promising non-precious, noble-metal-free catalysts. Herein, a unique precursor directed approach is introduced for preparing a cobalt ferrite@nitrogen doped carbon nanohorns (CoFe₂O₄@N-CNHs) nanohybrid catalyst in a single step annealing process involving stoichiometric amounts of single-source cobalt and iron molecular precursors and carbon nanohorns (CNHs) under an argon/ammonia (Ar/NH₃) atmosphere. This procedure enables a simultaneous CoFe₂O₄ ferrite synthesis and nitrogen functionalization of CNHs. The precious metal free nanohybrid CoFe₂O₄@N-CNHs-30% containing 30% of carbon presents an oxygen reduction reaction (ORR) half wave potential and onset potential comparable to the standard ORR catalyst 20% Pt/C. CoFe₂O₄@N-CNHs-30% also establishes superior oxygen evolution reaction (OER) performance with a low overpotential and a small Tafel slope than benchmark OER catalyst RuO₂. Furthermore, the rechargeable zinc-air battery with the CoFe₂O₄@N-CNHs-30% nanohybrid as air electrode demonstrates steadier and more durable charge–discharge cycles, and outstanding energy density relative to the state-of-the-art 20% Pt/C-RuO₂ catalyst.