Supercapacitor and oxygen evolution reaction performances based on morphology-dependent Co-MOFs

A series of the Co-MOF materials with different crystallinities have been synthesized under various conditions, including reaction time, temperature and pressure. The structures and morphologies of the Co-MOF materials have been characterized by powder X-ray diffraction (XRD), N2 adsorption-desorption isotherms and scanning electron microscopy (SEM). Electrochemical performances of the as-synthesized materials have been investigated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), endurance-life and oxygen evolution reaction (OER) tests. The results suggest that Co-MOF6h (the sample synthesized by hydrothermal method for 6 ​h) electrode attains the specific capacitance of 450.89 ​F ​g−1 at a current density of 0.5 ​A ​g−1 and shows higher supercapacitive performance than others. All the Co-MOF electrodes show high capacitance retention more than 95% over 1000 cycles. However, high-crystallinity Co-MOF72h (the sample synthesized by hydrothermal method for 72 ​h) exhibits best oxygen evolution reaction (OER) electrocatalytic activity with a low overpotential of 387 ​mV among as-synthesized Co-MOFs.