Synthesis of MnO₂ nanoparticles confined in ordered mesoporous carbon using a sonochemical method

A sonochemical method has been successfully used in order to incorporate MnO₂ nanoparticles inside the pore channels of CMK-3 ordered mesoporous carbon. Modification of the intrachannel surfaces of CMK-3 to make them hydrophilic enables KMnO₄ to readily penetrate the pore channels. At the same time, the modification changes the surface reactivity, enabling the formation of MnO₂ nanoparticles inside the pores of CMK-3 by the sonochemical reduction of metal ions. The resultant structures were characterized by X-ray diffraction (XRD), nitrogen adsorption, and transmission electron microscopy (TEM). CMK-3 with 20 wt.-% loading of MnO₂ inside CMK-3 delivered an improved discharge performance of 223 mA h g ^-1 at a relatively high rate of 1 Ag^-1. Almost no decrease in specific capacity is observed for the second cycle, and a discharge capacity of more than 165 mA h g^-1 is retained after 100 cycles. This is attributed to the nanometer-sized MnO₂ formed inside CMK-3 and the high surface area of the mesopores (3.1 nm) in which the MnO₂ nanoparticles are formed.