Carbons with narrow pore size distribution prepared by simultaneous carbonization and self-activation of tobacco stems and their application to supercapacitors

Abstract

Highly microporous carbons with narrow pore size distribution have been prepared by simultaneous carbonization and self-activation of tobacco wastes at temperatures ranging from 600 to 1000 °C. The efficiency of porosity development, without pores broadening, is attributed to well-distributed alkalis at the molecular level in the tobacco precursor. With Burley tobacco, the BET specific surface area and average micropore size L0 increased up to 800 °C (Burley 800), where the values reached maxima of 1749 m2 g-1 and 1.2 nm, respectively. At temperatures higher than 800 °C, annealing of the materials dominates and provokes a decrease of SBET and L0. Burley carbons were implemented in supercapacitors using 1 mol L-1 aqueous Li2SO4 or 1 mol L-1 TEABF4 in acetonitrile. In both electrolytes, the capacitance of Burley carbons followed the same trend as SBET and L0. Burley 800 demonstrated outstanding capacitance values of 167 F g-1 (at 0.8 V limit) and 141 F g-1 (at 2.3 V limit) in 1 mol L-1 aqueous Li2SO4 and 1 mol L-1 TEABF4, respectively. Such values, about 50% higher as compared to commercially available carbons, are attributed to the narrow pore size distribution of this carbon with a maximum of pores around 1.2 nm close to the size of solvated ions in these electrolytes.