IMPROVED CAPACITIVE BEHAVIOR OF MnO₂ THIN FILMS PREPARED BY ELECTRODEPOSITION ON THE PT SUBSTRATE WITH A MnOx BUFFER LAYER

Nanostructured MnO 2 thin films were prepared on two types of substrates, Pt / Ti / SiO 2 / Si (PT) and MnO x / Pt / Ti / SiO 2 / Si ( MnO x / PT ), by the technique of cyclic-voltammetric electrodeposition. The MnO x buffer layer was deposited on the PT substrate by pulsed laser deposition (PLD). The as-deposited MnO 2 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 MnO 2 electrodes were investigated using cyclic voltammetry (CV) in 1 M Na 2 SO 4 electrolyte. It was found that the adhesion between the MnO 2 film and the Pt substrate was poor, resulting in cracks and peeling of the MnO 2 film after deposition. However, the adhesion of the MnO 2 film with the MnO x buffer layer was greatly improved, resulting in superior pseudocapacitive performance of the thin film electrodes. A specific capacitance of about 364 F/g of MnO 2 thin films deposited on the MnO x 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 MnO 2 thin film deposited on the MnO x / PT substrate exhibits good rate capability and excellent cycle performance, which makes it promising for supercapacitor application.