Hierarchically porous carbons with partially graphitized structures for high rate supercapacitors

Partially graphitized hierarchically porous carbons (denoted as GHPCs) were prepared by using ordered mesoporous nickel oxide as template. The mesoporous nickel oxide, which is different from the inert template such as mesoporous silica SBA-15, plays an important role in the synthesis of the carbons with partially graphitized nanostructures at high temperature. X-ray diffraction, transmission electron microscopy and nitrogen adsorption were employed to characterize the structure of GHPCs. It is shown that the GHPC obtained by calcinating the precursor at 700 degrees C has a hierarchically porous structure with the pore size distributions at 8 and 30 nm. Partially graphitized structure leads to the high electrical conductivity of GHPCs. The GHPC prepared at 700 degrees C (GHPC700) shows outstanding high rate performance. Its specific capacitance reaches 91 F g(-1) at a potential scan rate of 500 mV s(-1). Meanwhile the specific capacitance for the GHPC prepared at 600 degrees C (GHPC600) is only 46 F g(-1) at the same scan rate. Synergistic effect of the efficient ion transport in hierarchically porous structure and the high electrical conductivity owing to the partially graphitic structure is contributed to the attractive electrochemical performance of GHPC700.