Na-bimessite-type MnO2 (Na-CL-1) nanoplates and sodium manganese dioxide nanobelts with a 2 x 4 tunnel (Na-OMS-5) were synthesized by a hydrothermal method via one-pot oxidation reaction at 120 and 200 degrees C, respectively. The microstructure, morphology, and thermal stability of the MnO2 products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, simultaneous thermogravimetric-mass spectrometry, and N-2 adsorption-desorption measurements. Their electrochemical performance was investigated in order to understand the sodium ions intercalation - deintercalation processes in the lamellar or tunnel structure of MnO2. Na-CL-1 nanoplates exhibited a specific capacitance of 308 F g(-1) at a current density of 0.2 A g(-1), which is much higher than that of Na-OMS-5 nanobelts (141 F g(-1)). Moreover, the Na-CL-1 nanoplates showed a good rate capability and electrochemical stability, suggesting that it is a promising electrode material for supercapacitors. (C) 2014 Elsevier Ltd. All rights reserved.