Multifunctional CoWO₄ 2D Array Electrode for Electrocatalytic Overall Water Splitting and Supercapacitor Application

Rational design and construction of 2D materials play a crucial role in energy storage and conversion technologies. Herein, we used a cation-exchange strategy, followed by a thermal treatment to develop CoWO4 2D sheets using Co-MOF as a template. The porous rough CoWO4 2D sheets integrated on the nickel foam displayed an excellent electrocatalytic performance toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at an overpotential of 177 and 139 mV to realize the benchmark current density of 10 mA cm(-1). Moreover, we demonstrated the OER and HER performance in a single cell using 2D-CoWO4@NF as a cathode and an anode and delivered 10 mA cm(-2) current density at a cell potential of 1.51 V. The supercapacitor performance of 2D-CoWO4@NF was also investigated, which exhibited a specific capacity of 1196.7 C g(-1) (2659.3 F g(-1)) at a current density of 3 A g(-1) in a three-electrode system. An asymmetric device was constructed using 2D-CoWO4@NF as the positive and activated charcoal (AC) as the negative electrode, which delivered an energy density of 79 W h kg(-1) at a power density of 2.25 kW kg(-1).