Nitrogen-doped carbon nanoparticles are attracting increased attention for CO2 capture due to the low energy consumption associated with CO2 regeneration (less than 40 kJ/mol CO2). Carbon nanoparticles with highly accessible surface area facilitate the diffusion kinetics of the CO2 molecule. However, nanoparticles may not be as efficient adsorbents due to mass loss and pressure drop when installed in adsorption columns, e.g. packing column. In such case, macroscopic, bulk carbon is better suitable due to their better handability and higher packing constructions, but it sacrifices the benefits that otherwise arise from nanoscaled materials, such as the high and fast uptake and release of CO2. Herein, we bridge the advantages of the nano and the macroscale by self-assembling 400-nm lignin particles – a biosource for carbon – into milimetric supraparticles (SPs). We present a versatile self-assembly methodology that introduces cellulose nanofibrils (CNF) as binder to enhance cohesion while preserving the inherent nano-morphologies. SPs were prepared by evaporating the aqueous droplets containing lignin nanoparticles and CNF onto a superhydrophobic substrate. The SPs, comprising 1-15 wt. % CNF, display extremely high mechanical resistance owing to the entangled CNF-particle network. The carbonization of the lignin-CNF SPs produces pomegranate-like carbon SPs with improved strength. Low amounts of CNF allow a partial melting of the lignin’s primary particles during carbonization. Higher amounts of CNF hinder the interparticle connections and create high defect volume across the SP upon carbonization. The SPs were pre-oxidized by slow heating in air before carbonization to turn the lignin system from a thermoplastic to a thermoset. The carbon SPs were subsequently activated by blowing N2 through ammonia aqueous solution into the furnace tube, allowing control on the porosity and nitrogen content. Specific surface area of 2000 m2/g and 5.5 wt. % nitrogen content were obtained. The lignin-based carbon SPs adsorbs CO2 at concentration as high as 80 mg/g at 40 °C, which is highly competitive compared to the most recent literature. By self-assembling lignin nanoparticles into macroscopic supraparticles, we created a system with a three-level hierarchy as far as porosity: micropores within the primary particles, mesopores in nanoparticle interstices, and macropores when packing the SPs upon application.

Nitrogen-doped lignin-derived carbon supraparticles for CO2 adsorption

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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