Cellulose-Solvent-Assisted, One-Step Pyrolysis to Fabricate Heteroatoms-Doped Porous Carbons for Electrode Materials of Supercapacitors

A low-priced, ecofriendly and sustainable strategy to fabricate materials of superior electrochemical property is of paramount importance for the development of supercapacitors (SCs). Herein, heteroatoms-doped porous carbons (HPCs) were prepared from waste newspapers (WNPs) with the assistance of cellulose solvent, i.e., aqueous solution consisting of NaOH, urea, and thiourea (NUT, for short); subsequently, the resultant HPCs were applied as materials for SCs electrodes. Innovatively, the NUT solution acts simultaneously as solvent for WNPs, activating agent, and co-dopants (N, S, and O) in the subsequent preparation of HPCs materials. Interestingly, the porous structure and doping content of HPCs are tunable by changing the related feed ratio between NaOH and WNPs (W-NaOH/W-WNPs = 0.5, 1.0, and 1.5), along with the pyrolysis temperature (600, 700, and 800 degrees C). The appropriate porosity along with the surface doped by heteroatoms (N, S, and O) of the obtained HPCs result in superior electrochemical performance endowing them with potential for high performance SCs. CS3-T800 exhibits a maximum specific capacitance of 308 F g(-1) (1 A g(-1)) and excellent cycle capability (94.0% of capacitance retention after 5000 charge/discharge cycles) in a three-electrode system. Moreover, the CS3-T800-based symmetric SCs exhibit a energy density of 10.48 Wh kg(-1) and power density of 250 W kg(-1), all making it a promising electrode material for SCs. The enhancement mechanism for the porous carbon electrode reveals that rationally designed mesopores and micropores are more critical in porous electrode performance. This work hereby provides an excellent paradigm to produce highly porous and conductive carbons from biomass like WNPs for various energy-storage applications.