Hierarchically porous graphitic carbon particles are prepared by an aerosol process using a aqueous solution of a carbon precursor compound in which different sized particles or clusters of silicon oxide species are dispersed. The aerosol is heated to evaporate the solvent. The solid residue is carbonized and non-carbon species removed to obtain small porous particles of graphitic carbon. The interconnected, different size pores in the small carbon particles make them very useful as electrode materials in electrochemical devices, such as supercapcitors, in which efficient ion transport through the pores or the particles is required.