Effects of Cellulose, Hemicellulose, and Lignin on the Structure and Morphology of Porous Carbons

Porous carbon materials stemming from biomass have drawn increasing interest because of their sustainable properties. Cellulose, hemicellulose, and lignin are the three basic components of crude biomass, and were investigated to reveal their influence on the derived carbonaceous materials. Huge amounts of oxygen-containing functional groups in cellulose and hemicellulose tend to be eliminated as H2O, CO2, and CO and give micropores during pyrolysis, whereas lignin contains plentiful aromatic units which are chemically inert, and thus produce nonporous carbon materials. When the KHCO3 was introduced during the pyrolysis process, the plentiful hydroxyl in cellulose and hemicellulose underwent dehydration condensation among different parent polymers, which are responsible for the formation of macroporous structure. By contrast, The β-O-4 bands in lignin experience homolysis and give rise to benzene-containing units, which finally result in carbon nanosheets. Furthermore, we demonstrated the mixture of cellulose, hemicellulose, and lignin can display a three-dimensional porous structure (containing macropores, mesopores, and micropores) when less than 50% of lignin is contained.