Bifunctional MOF-on-MOF-Derived CuCo2O4 for Oxygen Evolution Reaction Electrocatalysis and Supercapacitor Electrodes.

The development of high-performance electrocatalysts for oxygen evolution reaction (OER) is still a challenge to produce green hydrogen. Thus, herein, a new bifunctional metal-organic frameworks (MOF)-derived CuCo₂O₄ is obtained, applied as OER electrocatalyst and electrode for supercapacitors. All physicochemical and morphological characterization indicates the formation of a pure spinel structure CuCo₂O₄ crystalline phase and coral reef-like morphology. X-ray photoelectron spectroscopy data showed major presence of Co³⁺ and Cu⁺ ions on the surface and high concentration of oxygen vacancies. OER electrocatalytic assays conducted in alkaline medium (1.0 M KOH) show a reduced overpotential (η) of 317 mV at 10 mA cm^-2 and Tafel slope of only 49 mV dec^-1, besides excellent electrochemical stability up to 12 h. The material is also studied for supercapacitors applications via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis. CuCo₂O₄ material presents specific capacity near 75 C g^-1, at least ≈2.8 times higher than pristine CuO and Co₃O₄ at 1 A g^-1. This results indicate the MOFs-derived CuCo₂O₄ as a promising bifunctional material for energy conversion and storage.