Surface-enhanced OER activity in Co 3 V 2 O 8 using cyclic charge-discharge to balance electrocatalytic active site generation and degradation

Here, we demonstrate a material design strategy to enhance the electrocatalytic activity for oxygen evolution reaction (OER) by repetitive charge/discharge supercapacitor cycling of Co 3 V 2 O 8. The charge/discharge cycle helps to alter the electronic structure via stabilizing more active components on the surface and increases the electronic conductivity by increasing the oxygen vacancies. X-ray photoelectron spectroscopy and X-Ray Diffraction assists in identifying the chemical states and the structure of different components. The electrochemical techniques suggest that an increase in Co 3+ on the surface with the available oxygen vacancies at 2500 charge/discharge cycled sample promotes intermediates like CoOOH, which help in decreasing the overpotential for the OER. We report specific current density with respect to the electrochemical surface area (ECSA), and our best sample shows a specific activity of ~6.2 µA/cm 2 ECSA with Tafel slope 85.12mV/dec. Further, the reaction mechanism and different interfacial resistances are identified with the help of electrochemical impedance spectroscopy. This study suggests that an optimum number of charge/discharge cycles are needed to balance the competing factors of electrocatalysts activation and decomposition of the active material.