A new approach for the synthesis of electrocatalytically active CoFe₂O₄ catalyst for oxygen reduction reaction

Abstract

Synthesis of non-precious electrocatalyst for the reduction of oxygen is of significant interest in the development of electrochemical energy conversion devices. Herein, we demonstrate a new, low-cost, and facile non-hydrothermal approach for the synthesis of electrocatalytically active spinel CoFe₂O₄ by thermal annealing of the multimetal complex, potassium cobalt hexacyanoferrate [K₂CoFe(CN)₆]. The as-synthesized CoFe2O4 is characterized by spectroscopic, electron microscopic and electrochemical techniques. The polyhedral-shaped crystalline CoFe₂O₄ particles have size ranging from 200 to 300 nm. The CoFe2O4 catalyst is integrated with reduced graphene oxide (rGO) and its electrocatalytic activity toward oxygen reduction reaction is evaluated. The integrated hybrid catalyst rGO/CoFe₂O₄ favors the 4-electron reduction of oxygen to water at low overpotential in alkaline pH with Tafel slope of 63 mV dec⁻¹. The hybrid catalyst (rGO/CoFe₂O₄) has high durability and methanol tolerance. The catalytic performance is superior to that of the as-synthesized CoFe₂O₄ and rGO. The enhanced electrocatalytic performance is ascribed to the synergistic effect of CoFe₂O₄ and rGO, large surface area and high electronic conductivity. The ideal integration of CoFe₂O₄ with electronically conducting rGO favor the facile diffusion and promote the electron transfer for the reduction of oxygen.