Metal–Organic Framework Derived Hybrid Co₃O₄‑Carbon Porous Nanowire Arrays as Reversible Oxygen Evolution Electrodes

Hybrid porous nanowire arrays composed of strongly interacting Co₃O₄ and carbon were prepared by a facile carbonization of the metal–organic framework grown on Cu foil. The resulting material, possessing a high surface area of 251 m² g^–1 and a large carbon content of 52.1 wt %, can be directly used as the working electrode for oxygen evolution reaction without employing extra substrates or binders. This novel oxygen evolution electrode can smoothly operate in alkaline solutions (e.g., 0.1 and 1.0 M KOH), affording a low onset potential of 1.47 V (vs reversible hydrogen electrode) and a stable current density of 10.0 mA cm^–2 at 1.52 V in 0.1 M KOH solution for at least 30 h, associated with a high Faradaic efficiency of 99.3%. The achieved ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the state-of-the-art noble-metal/transition-metal and nonmetal catalysts, originate from the unique nanowire array electrode configuration and in situ carbon incorporation, which lead to the large active surface area, enhanced mass/charge transport capability, easy release of oxygen gas bubbles, and strong structural stability. Furthermore, the hybrid Co₃O₄-carbon porous nanowire arrays can also efficiently catalyze oxygen reduction reaction, featuring a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal–air batteries, regenerative fuel cells, and other important clean energy devices.