Manganese dioxides octahedral molecular sieve nanowires with 2 x 2 tunnels (designated OMS-2) and amorphous manganese dioxides were synthesized via a hydrothermal treatment and a sol-gel method, respectively. Amorphous MnO2 nanoparticles were incorporated into the matrix of OMS-2 nanowires to form homogenous nanocomposites. The structures and morphologies of as-synthesized OMS-2 nanowires and amorphous MnO2 nanoparticles were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Electrochemical behaviors of the as-prepared nanocomposites with varying ratios were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and potentiostatic electrochemical impedance spectroscopy (EIS) using a three-electrode system in a 0.5 M Na2SO4 aqueous solution. Pure OMS nanowires exhibit a specific capacitance of about 37 Fg(-1), and amorphous MnO2 nanoparticles demonstrate relatively higher specific capacitance of about 106 Fg(-1) at a scan rate of 2 mV s(-1). The enhancement of specific capacitance can be carried out by mixing OMS-2 nanowires and amorphous MnO2 nanoparticles to form nanocomposites and the optimized mole ratio of OMS-2 nanowires to amorphous MnO2 as 1:5 can be achieved. The improved specific capacitance can be attributed to the increase of electrode conductivity and the effective interfaces between MnO2 active materials and electrolyte. (c) 2012 Published by Elsevier Ltd.