A facile template-free synthesis of α-MnO2 nanorods for supercapacitor

Manganese dioxide nanorods were synthesized by a facile method through simply refluxing the reaction mixture of KMnO4 and MnCl2 solution in the presence of K2Cr2O7. The products were characterized by X-ray powder diffraction and scanning electron microscopy. α-MnO2 nanorods with diameters of 50–100 nm and lengths of 0.5–2 μm were formed depending on the amount of K2Cr2O7 together with the reflux time. The formation mechanism of the α-MnO2 nanorods was discussed in detail. The electrode performance of manganese dioxide for use as capacitor was studied by cyclic voltammetry (CV) and galvanostatic charge–discharge. The α-MnO2 nanorods which were prepared with a mass ratio of K2Cr2O7 to KMnO4 of 1:10 exhibited good electrochemical performance, and a specific capacitance as high as 245 F g−1 was measured at a current density of 1 A g−1.

► MnO2 nanorods have been synthesized by a facile refluxing method.
► α-MnO2 nanorods with diameters of 50–100 nm and lengths of 0.5–2 μm.
► The K2Cr2O7 amount and reflux time affect the nanorod formation.
► The dissolution and recrystallization are responsible for the nanorod formation.