Pulsed laser deposition of cobalt-doped manganese oxide thin films for supercapacitor applications

Abstract

Thin films of manganese oxide doped with various percentages of cobalt oxide were grown by pulsed laser deposition on silicon wafers and stainless steel substrates. The films were characterized by X-ray diffraction and field emission scanning electron microscopy in order to identify their phases and microstructures. The pseudo-capacitance behavior of the Co-doped manganese oxide films were then evaluated using electrochemical cyclic voltammetry in an aqueous electrolyte. Their specific current and capacitance determined by electrochemical measurements were compared with undoped manganese oxide films, and the results show that Co-doped amorphous MnO x films have significantly higher specific current and capacitance than undoped amorphous MnO x films. The 3.0% Co-doped MnO x (i.e., Mn 0.970Co 0.030O x ) film had the highest specific capacitance of 99 F g −1 at a 5 mV s −1 scan rate. However, Co-doped crystalline Mn 2O 3 films did not show an improvement in specific current and capacitance compared with undoped Mn 2O 3 crystalline films. High Co doping level (20.7% doped) in the crystalline Mn 2O 3 films actually decreased both the specific current and capacitance values. These findings demonstrate that elemental doping is an effective way to improve the performance of pseudo-capacitive metal oxides.