Harvest pitch-based carbon nanosheets by oxidation and in-situ template strategy for all-solid-state supercapacitors

Abstract

Transforming coal tar pitch (CTP) into porous carbon nanosheets (PCNS) offers a dual advantage: maximizing the value of CTP while pioneering novel carbon materials. A key challenge in synthesizing pitch-based PCNS lies in the hydrophobic nature and polycondensation of polycyclic aromatic hydrocarbons (PAHs) in CTP, limiting the integration of water-soluble additives and the formation of desired pore structures. In this study, oxidation process, commonly used in preparing pitch-based carbon fibers, was introduced into the synthesis pitch-based PCNS to address the aforementioned challenges. Through oxidization modification, hydrophilic functional groups rich in O, N and P were introduced to PAHs, while macromolecules were partially broken down into smaller aromatic compounds. Following oxidation, the carbon nanosheet structure was successfully achieved through co-carbonization of oxidized CTP and urea, during which the structure-directing agent C3N4 was generated in-situ. Moreover, the efficacy of oxidation modification in the formation of nanosheet structures was assessed by comparing the structures of porous carbon derived from CTP both pre- and post-oxidation. In final, pitch-based PCNS were used in supercapacitors. In three-electrode system, capacitance of PCNS attained 331.3 F/g at 0.5 A/g, and its response speed, capacitance retention rate and ion transfer speed were also excellent. For solid state supercapacitor, its energy density and cycle stability after 10,000 cycles were 8.3 Wh/kg and 92.4%, respectively.