Porous Ag-doped MnO₂ thin films for supercapacitor electrodes

In this study, MnO₂ was composited with different concentrations of Ag as dopant through a sol-gel method and deposited on the ITO glass substrates to form composite thin films. X-ray diffraction revealed the successful synthesis of crystalline structures while X-ray photoelectron spectroscopy showed the proper chemical compositional properties of MnO₂ and elemental Ag. Field emission scanning electron microscopy was used to observe the cross-sectional features at the edge and mesoporosity on the surface. Different electrochemical measurements were carried out in the LiCl/PVA gel electrolyte to investigate the optimum amount of Ag dopant in composites to achieve good electrochemical properties for use as supercapacitor electrodes. The highest mass specific capacitance of 306 F g⁻¹ was observed at an Ag dopant concentration of 7.5 at.% with a current density of 1 A g⁻¹. After 10,000 cycles, the capacitance decrease was less than 5% of the initial capacity and thus, exhibited a good long-term stability. The optimum concentration of Ag dopant and the mesoporous morphology were found to be of crucial importance in enhancing the electrical conductivity and the electrochemical performance of the MnO₂ films.