Ag-doped manganese oxide prepared by electrochemical deposition on carbon fiber for supercapacitors

摘要

Ag-doped manganese oxide was deposited on carbon fiber via a cathodic reduction method, then the deposits were dehydrogenized and oxidised by heat treatment at 350 degrees C for 4 h. Scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy were utilized to characterize the structure and state of the deposits. The results show that manganese oxide presents an amorphous fibrous structure and is a mixture of tetravalent and trivalent. The cyclic voltammetry curves measured with three-electrode methods in 0.5 M Na2SO4 electrolyte reveal that the specific capacitance of manganese oxide without and with Ag is about 450 and 825 F g(-1) at the scan rate of 5 mV s(-1), respectively. Hence, Ag doping improves the pseudo-capacitor behavior. The MnOx-based supercapacitors fabricated with 0.5 M Na2SO4 as electrolyte are characterized by cyclic voltammetry and galvanostatic charge-discharge to investigate the electrochemical properties. In order to study the cycle life of the devices the galvanostatic charge-discharge process is cycled 3000 times and the specific capacitance shows almost no change after 3000 cycles.