Oxygen-vacancy-rich spinel CoFe2O4 nanocrystals anchored on cage-like carbon for high-performance oxygen electrocatalysis

We report spinel-type CoFe2O4 nanocrystals (NCs) synthesized through facile hydrothermal growth and their attachment on a cage-like carbon (CC) for efficient and durable oxygen evolution/reduction reaction (OER/ORR) performance. As a catalyst, the so-constructed CoFe2O4 NCs show significantly higher OER performance than bare CoFe2O4 and CC, leading to an overpotential of 1.59 V for the OER at a current density of 10 mA/cm. Furthermore, CoFe2O4 NCs on CC electrodes also exhibit good ORR performance, which is comparable to Pt/C, significantly higher than that of bare carbon fiber paper, and acts as a bifunctional electrocatalyst. The CoFe2O4 NCs anchored on the CC electrodes exhibit remarkably long-term stability, which is evaluated by continuous cycling (over 5,000 cycles), without any morphological change, but preserving all the materials within the electrode. The results indicate that the CoFe2O4 NCs have a promising potential for efficient, cost-effective, and durable oxygen electrocatalysis at large scales using earth-abundant materials and low-cost fabrication processes.