Post-engineering of solution plasma-derived carbons via thermal air treatment for supercapacitor electrodes with enhanced capacitive performance

Carbon materials produced by solution plasma process (SPP) typically exhibit insufficient surface area and deficient microporosity, limiting their application in supercapacitor electrodes. Thus, post-engineering strategies are necessary to overcome this limitation. In this study, carbon nanoparticles (CNPs) were synthesized from benzene by SPP and subsequently subjected to thermal air treatment (TAT) under mild conditions (300 and 400 °C in an air atmosphere). The resulting CNPs had uniform morphology and an amorphous structure. With increasing TAT temperature, the specific surface area of CNPs increased from 171 to 575 m 2 g −1 through the development of micropores and mesopores. TAT also enriched the acidic oxygen functional groups on the surfaces of the CNPs. The electrochemical charge storage properties of the CNPs were investigated using a three-electrode system in a 1 M H 2 SO 4 electrolyte. The CNPs with TAT at 400 °C demonstrated the highest specific capacitance of 130 F g −1 at a current density of 1 A g −1, which was 5.4 times higher than that of the untreated CNPs (24 F g −1 ). It also exhibited stable cycling performance after 5000 charge–discharge cycles. This study demonstrates that TAT is a simple and effective post-engineering strategy for increasing the specific surface area and micro–mesoporosity of SPP-derived CNPs, as well as modifying their surface chemistry. These improvements enable the practical application of CNPs produced by SPP in the field of supercapacitors.