An Efficient Bi-functional Electrocatalyst Based on Strongly Coupled CoFe 2 O 4 /Carbon Nanotubes Hybrid for Oxygen Reduction and Oxygen Evolution

Cobalt ferrite (CoFe2O4) spinel oxide is a promising electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the catalytic activity of CoFe2O4 is limited by its poor electronic conductivity. In this study, CoFe2O4 strongly coupled with carbon nanotubes (CoFe2O4/CNTs) hybrid has been fabricated to address this issue. The as-synthesized CoFe2O4/CNTs hybrid exhibits excellent electrocatalytic activities for both the ORR and OER in alkaline solution. The onset potential of CoFe2O4/CNTs for ORR is −0.124 V (vs. Ag/AgCl), which is much higher than that of the CoFe2O4 + CNTs mixture (−0.259 V). Meanwhile, the CoFe2O4/CNTs hybrid shows much higher activity for OER as compared to the CoFe2O4 + CNT mixture. The onset potential of the former is 54 mV higher than that of the latter. The CoFe2O4/CNTs also holds high stability for both the ORR and OER, outperforming the CoFe2O4 + CNTs mixture. The excellent electrocatalytic activity and stability of the CoFe2O4/CNTs hybrid for both the ORR and OER make it a potential bi-functional electrocatalysts for metal-air batteries.