Molten Salts Derived Copper Tungstate Nanoparticles as Bifunctional Electro-Catalysts for Electrolysis of Water and Supercapacitor Applications

Abstract

Herein, we report molten salts derived, cube-shaped CuWO4 nanoparticles (50±5 nm) as multi-functional catalysts in electrochemical and photo-electrochemical studies. The formation of pure phase cube-shaped CuWO4 nanoparticles (CWO-NPs) is analyzed by X-ray diffraction, Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and field-emission electron microscopy (FE-SEM and FE-TEM). CWO-NPs show remarkable bi-functional electro-catalytic behavior for the oxygen evolution (OER) and oxygen reduction reactions (ORR) in 1.0 M KOH electrolyte solution. Polarization studies of CWO-NPs exhibit low over-potential (∼260 mV) at 1 mA/cm2 and low Tafel slope value (∼190 mV/dec) for OER compared to bulk or other oxides. Polarization studies with controlled electrode rotation reveal a four-electron pathway for the water electrolysis reaction for OER/ORR. In addition, CWO-NPs show promising capacitive behavior with specific capacitance values of ∼230 F/g using 1 M KOH electrolyte. Galvanostatic charge-discharge (GCD) studies of CWO-NPs displays low energy loss during discharge time for 50 segments. To further investigate the potential for industrial applications, the stability of the electrodes is also examined using chrono-amperometry (CA) at fixed potential, chrono-potentiometry (CP) at fixed current density, and cyclic voltammetry (CV) with 50 cycles.