Porous wood carbon monolith for high-performance supercapacitors

A surface modified porous wood carbon monolith (m-WCM) with high consistency and large porosity was successfully synthesized by carbonization of poplar wood and subsequent surface modification with HNO3 solution. The pore properties of obtained m-WCM, including the BET surface area, pore volume, and pore size distribution of these activated carbons were characterized by the N2 adsorption isotherms. The surface functional groups were characterized by Fourier transform infrared spectroscopy. Surface morphology and microstructure were physically characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained m-WCM was studied as electrodes for supercapacitors and exhibited excellent electrochemical performance compared with typical activated carbon (AC) and ordered mesoporous carbon (CMK-3). The effects of modification conditions on supercapacitive behavior were systematically studied, a maximum gravimetric capacitance (Cm) and volumetric capacitance (Cv) of 234 F g−1 and 36 F cm−3 were obtained in 2 M KOH solution. Long-term cycling experiments showed excellent stability with a reduction of the initial capacitance values of 3% after performing 2000 galvanostatic cycles at 10 mA cm−2.