Ultrafine microporous and mesoporous activated carbon fibers from alkali lignin

A facile and sustainable approach has been successfully devised to fabricate ultrafine (100-500 nm) highly porous activated carbon fibers (ACFs) by electrospinning of aqueous solutions of predominantly alkali lignin (low sulfonate content) followed by simultaneous carbonization and activation at 850 degrees C under N-2. Incorporating a polyethylene oxide (PEO) carrier with only up to one ninth of lignin not only enabled efficient electrospinning into fibers but also retained fibrous structures during heating, alleviating the need for a separate thermal stabilization step. In situ impregnation of alkali hydroxide activating chemicals with only up to 50% of the lignin carbon precursor, i.e., merely one tenth to one quarter of the quantities used in manufacturing activated carbon particulates, allowed simultaneous carbonization and activation in a single heating step. A range of micropore-dominant to mesopore-dominant ACFs were successfully fabricated to achieve superior specific surface (>1400 m(2) g(-1)) and porosity (>0.7 cm(3) g(-1)) tuned by varying the type and contents of alkali hydroxides. This streamlined approach was robust and demonstrated the feasibility and versatility in processing and converting a readily available renewable carbon precursor, lignin, into highly porous activated carbon fibers.