Low temperature and highly efficient oxygen/sulfur dual-modification of nanoporous carbon under hydrothermal conditions for supercapacitor application

How to modify carbon materials in a highly efficient manner is an important issue for the practical application. In this work, we demonstrate a hydrothermal approach for modifying nanoporous carbon using H 2 O 2 and H 2 SO 4 as oxygen/sulfur dopants, which can realize the purpose of achieving highly O/S doping. It reveals that hydrothermal temperature and dosage of H 2 SO 4 exert crucial roles for determining the carbon structures and capacitive performances. The change of temperature affects the reaction process, changes the degree of oxidation of carbon by H 2 O 2 , and changes the number of oxygen-containing functional groups on carbon surface. Under constant temperature conditions, H 2 SO 4 , as a strong oxidizing acid, changes in its dosage will affect the oxidation strength of the system, while changing the number of oxygen-containing functional groups, increasing a certain amount of sulfur-containing functional groups. The specific capacitance of microporous carbon increases from 43 to 168 F g −1 , nearly 3.5 times, at a scan rate of 100 mV s −1 in 6 M KOH aqueous electrolyte, under the action of oxygen-containing functional groups, and the cycle stability is also as high as 92%, which is higher than 90% of untreated nanoporous carbon. The energy density of the modified sample is 5.49 Wh kg −1 at the power density of 0.5 kW kg −1 . In addition to improving the wettability of carbon materials, oxygen-containing functional groups also produce pseudocapacitance by redox reaction.