Activated carbons derived from renewable resources have increased interest in replacing traditional materials in areas such as electrochemistry, catalysis, and gas/liquid purification. In recent years, the goal has been to increase the surface area and micropore volume of these activated carbons to improve their effectiveness. Lyophilization, the process of solidification then sublimation, can serve as an effective and environmentally friendly way to increase the porosity and micropore area of activated carbons derived from biomass. This study analyzed various lyophilization methods and how the freeze-drying process at different steps in the chemical activation process affects micropore formation and total surface area of activated carbons produced from cellulose nanofibers (CNF) and lignin. CNF/lignin activated carbons subjected to conventional drying showed similar structure and BET surface area to commercial samples. When lyophilization of the raw material was performed only before the pyrolysis process, a 144% increase in surface area and 172% increase in micropore volume was observed due to freeze-drying creating a porous organic framework that was maintained and further etched during the activation process. Post-activation lyophilization produced a final structure with a destroyed carbon framework that collapsed into a fine powder with minimal micropore volume. Our results convey that lyophilizing biomass mixtures of cellulose nanofiber and lignin before pyrolysis takes place provides an environmentally friendly way to improve microstructure properties of chemically activated carbons to enable their use more effectively in potential applications.

Microstructure of activated carbons produced from cellulose nanofibers and lignin

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.