Organic salt-assisted pyrolysis for preparation of porous carbon from cellulose, hemicellulose and lignin: New insight from structure evolution

Abstract

Developing green, high efficient and precursor-universal pore tailoring approach is a major issue for biomass-derived porous carbon (BPC). In this study, the unique effect of organic salt porogen (potassium acetate) was first elucidated through investigating the component and temperature-dependent structure evolution of BPC during pyrolysis-activation process. Hydrogen bonding with biomass char rather than melting would facilitate the dispersion of porogen. Potassium acetate would catalyze cracking of biopolymers (<400 ℃) into H2, CO2, CO and CH4 etc. and lead to plentiful macropores by gas blowing. And it decomposed into potassium species that etch the char to form micropores. Differently, cellulose and hemicellulose char intermediates with abundant carbonyl incline to retain the porous structure. BPCs from cellulose and hemicellulose possess specific surface area (SSA) ~ 1700 m2/g with nano-passages and three-dimensional layer framework structure. While lignin-derived BPC performs equally high SSA but bulky microporous structure. Besides, carbon layer would form from acetate decomposition and deposited on the char surface thus lead to similar surface structure. This study provides a novel insight of interaction between biomass char intermediate and organic salt porogen, which may demonstrate a precursor-universal and high efficient approach for BPC preparation.