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

Abstract

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 °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 MnO_x-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.