IMPROVED CAPACITIVE BEHAVIOR OF MnO2 THIN FILMS PREPARED BY ELECTRODEPOSITION ON THE PT SUBSTRATE WITH A MnOx BUFFER LAYER
Abstract
Nanostructured MnO2 thin films were prepared on two types of substrates, Pt/Ti/SiO2/Si (PT) and MnOx/Pt/Ti/SiO2/Si (MnOx/PT), by the technique of cyclic-voltammetric electrodeposition. The MnOx buffer layer was deposited on the PT substrate by pulsed laser deposition (PLD). The as-deposited MnO2 thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the thin film MnO2 electrodes were investigated using cyclic voltammetry (CV) in 1 M Na2SO4 electrolyte. It was found that the adhesion between the MnO2 film and the Pt substrate was poor, resulting in cracks and peeling of the MnO2 film after deposition. However, the adhesion of the MnO2 film with the MnOx buffer layer was greatly improved, resulting in superior pseudocapacitive performance of the thin film electrodes. A specific capacitance of about 364 F/g of MnO2 thin films deposited on the MnOx buffer layer can be obtained at a scan rate of 10 mV/s in the voltage window between 0 and 0.9 V versus the Ag/AgCl reference electrode. The MnO2 thin film deposited on the MnOx/PT substrate exhibits good rate capability and excellent cycle performance, which makes it promising for supercapacitor application.
