Hybrid Nanostructure of Sputter Decorated Nanodots of Ag₂O/AgO over Flower-like Mn–Co–Cu Ternary Metal Oxide for Electrocatalytic Oxygen Evolution Reaction

Hybrid nanostructures of quaternary-composite metal oxide catalyst consisting of silver oxide nanodots over flower-like nanostructures of ternary metal oxide (MnCoCuO x ) were synthesized by a hydrothermal method, followed by DC magnetron sputtering. Multimetal ions in spinel structures are efficient OER catalysts as they have large number of active sites, enhancing the electron transfer process. The sputter decorated silver oxide nanodots enhances the electrochemically active surface area (ECSA) of the electrode, which further enhances the OER performance. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and Raman spectroscopy were used to validate the structure and composition of synthesized material. Oxygen evolution reaction (OER) activities of the synthesized catalysts were investigated by conducting linear scan voltammetry (LSV) at sweeping rate of 5 mV/s, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD). Quaternary-composite metal oxide catalysts were synthesized at various plasma powers, keeping other sputtering parameters fix. Silver oxide nanodots sputter decorated at 45 W over MnCoCuO x, showed the best catalytic properties for OER, having an overpotential of 83 mV via anodic scan and 110 mV via cathodic scan, Tafel slope of 65 mVdec –1, ECSA of 826 cm 2, mass activity of 143.7 A g –1, and a turn over frequency (TOF) of 0.039 s –1 . The symmetric device fabricated using the best performing electrode as cathode and anode displayed efficient water splitting activity, achieving a current density of 10 mA/cm 2 at 1.37 V vs RHE, which is close to thermodynamic value of 1.23 V.