Mesoporous carbons synthesized by direct carbonization of citrate salts for use as high-performance capacitors

A simple one-step synthesis methodology for the fabrication of mesoporous carbons with an excellent performance as supercapacitor electrodes is presented. The procedure is based on the carbonization of non-alkali organic salts such as citrate salts of iron, zinc or calcium. The carbonized products contain numerous inorganic nanoparticles (i.e. Fe, ZnO or CaO) embedded within a carbonaceous matrix. These nanoparticles act as endotemplate, which when removed, leaves a mesoporous network. The resulting carbon samples have a large specific surface area up to ∼1600 m2 g−1 and a porosity made up almost exclusively of mesopores. An appropriate heat-treatment of these materials with melamine allows the synthesis of N-doped carbons which have a high nitrogen content (∼8-9 wt.%), a large specific surface area and retain the mesoporous structure. The mesoporous carbon samples were employed as electrode materials in supercapacitors. They exhibit specific capacitances of 200-240 F g−1 in 1 M H2SO4 and 100-130 F g−1 in EMImTFSI/AN. More importantly, the carbon samples possess a good capacitance retention in both electrolytes (>50% in H2SO4 and >80% in EMImTFSI/AN at 100 A g−1) owing to their mesoporous structure which facilitates the penetration and transportation of ions.