Molybdenum-doped hexagonal birnessite as a promising electrode material of the electrochemical capacitor

The molybdenum-doped nanostructured birnessite with improved discharge capacity and desirable cyclic stability was synthesized by solvothermal method. The effect of molybdenum doping on supercapacitance performance of birnessite-type manganese oxides was investigated. The supercapacitance performances were characterized by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. The results indicate that the nanostructure sizes of manganese oxides composed of nanoflakes apparently decreased by the introduction of molybdenum. The nanostructure of manganese oxide doped with 15% in Mo/Mn + Mo molar ratio has the minimum size and the most homogeneous in particle size distribution. The highest specific capacitance of 202 F g^{− 1} with excellent cyclic stability is achieved when the content of doping molybdenum reached to 15% in Mo/Mn + Mo molar ratio. The mechanism of doped molybdenum in nanostructure and electrochemical performance was also discussed.