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.