A Potassium Formate Activation Strategy for the Synthesis of Ultrathin Graphene-like Porous Carbon Nanosheets for Advanced Supercapacitor Applications

Abstract

Ultrathin graphene-like porous carbon nanosheets (GPCNSs) have been proved to be promising candidates for electrochemical energy storage application in view of their extremely large accessible surface area and significantly shortened ion diffusion pathways in comparison with the traditional granular activated carbons. Nevertheless, the effective synthesis and practical application through the existing approaches still remain tremendous challenges owing to the thickness of the resulting carbon nanosheets that are rather thick as well as the extremely sophisticated synthetic procedures. Herein, we established an efficient strategy to produce ultrathin graphene-like porous carbon nanosheets from sustainable pine bark precursors. The most important distinction between our method and the existing protocols is the introduction of potassium formate as a new activation agent, which plays different roles during the carbonization–activation process. In this way, GPCNS with ultrathin thickness (∼3.8 nm) and a hierarchically porous structure with high mesopore proportion can be obtained, which displays extraordinary adaptability toward high energy/power supercapacitor in a nonaqueous electrolyte. Notably, the GPCNS-3-based supercapacitor has a specific capacitance retention ratio up to 76.3% at 40 A g–1 and an impressive energy density as large as 22.8 Wh kg–1 at an ultrahigh power density of 30.375 kW kg–1. The facile synthetic procedure coupled with the excellent electrochemical performance holds a great potential for future application in electrochemical energy storage field.