s Free-Standing Mesoporous Biocarbon Papers Based High-Rate Supercapacitor

Background: High performance carbon papers made from renewable carbon materials have the potential to boost the development of electrochemical energy technologies. Method: Free-standing and binder-free biocarbon papers have been successfully prepared through a simple one-step carbonization of thin sheets of pre-densified balsa wood. They exhibit an electrical conductivity of 0.16 S/cm and a carbon content higher than 95 wt%. The Brunauer-Emmett-Teller (BET) studies show that the biocarbon possesses a hierarchical porous structure characteristic of approximately 72% mesopores and 28% micropores with an average pore size of approximately 5.1 nm. On the surfaces of biocarbon papers, several functional groups associated with C-O, C=C, C=O, and N-O bonds were detected by the Fourier-transform infrared spectroscopy (FTIR) method. The X-ray diffraction and Raman studies show that the crystalline microstructures of the biocarbon are characterized by shorter stacks and larger atomic layer spacing compared to regular amorphous carbons. Results: A supercapacitor comprising of two biocarbon paper electrodes exhibited excellent highrate performance in sulfuric acid electrolyte, signaled by a rectangular current-voltage response even at scan rates higher than 10 V/s. Furthermore, no obvious performance decay was observed upon 20000 successive potential cycles. The results above suggest that the balsa-wood derived bio carbon papers could be a new class of promising electrodes for electrochemical applications.