Effect of synthesis methods on the surface and electrochemical characteristics of metal oxide/activated carbon composites for supercapacitor applications

Abstract

MnO2/Activated Carbon (cAC) and NiO/cAC composites were synthesized by both hydrothermal and precipitation methods in order to investigate the effect of preparation methods on the surface chemistry and porous structure of composite-based electrodes and electrochemical properties. X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), N2 physisorption, Raman spectroscopy and scanning electron microscopy (SEM) techniques were used to investigate the surface chemistry, chemical composition, pore characteristics and surface morphology of the synthesized composites. Synthesized composites were used as electrode materials within button cell supercapacitors. It was found that hydrothermal treatment to deposit the nano-oxides led to an increase in specific surface area, also this treatment resulted in oxygen-containing surface functionalities, which led to an improvement in electrochemical properties. Although the metal oxide loading caused a decrease in the specific surface area, the pseudocapacitive effect of MnO2 and NiO, and oxygen-containing surface functionalities increased the specific capacitance. MnO2 and NiO loading led to a 50% and 150% increase in specific capacitance, respectively. NiO/cAC samples obtained by precipitation method showed a higher specific capacitance compared to hydrothermally synthesized NiO/cAC. The metal oxide loading method has great influence on the surface chemistry, surface area and the resulting electrochemical performance of activated carbon-based fabricated supercapacitors.