The key to carbon aerogel microbeads: xanthan gum-mediated shape retention during gelation of resorcinol formaldehyde droplets

Kurzfassung

Their high porosity, high surface area, and low density render resorcinol-formaldehyde (RF) aerogels attractive precursors to their carbon analogs which have interesting applications, for instance in adsorption, catalysis, or electrochemical energy storage. While they are conventionally produced by pyrolysis as monoliths in a laboratory scale, a large-scale production would be more facile if they were produced in the form of microbeads. The direct bead formation of RF solution by the dropping method is limited because of their inability to preserve the spherical shape until gelation due to the low viscosity of RF solution. Therefore, within this work, we aimed to improve the viscosity by adding the polysaccharide-based thickener xanthan gum (XG) to the RF solution and pre-gelling them, followed by dropping into an acid bath for rapid gelation. We were thus able to produce RF aerogel beads (RFB) and subsequently carbon aerogel beads (CB) with diameters ranging from 2.0–2.6 mm. Here, we investigated the physicochemical properties of the resulting RF and CB using various physicochemical techniques by varying the XG concentration and the type of acid gelation bath. N2 physisorption analysis showed that CBs developed with high surface areas up to 1205 m2/g, micropore volumes up to 0.43 cm3/g and, bulk (tap) density of 0.31 g/cm3. In order to evaluate the use of these CBs for applications such as carbon capture and electrode material, we furthermore investigated their CO2 sorption capacity, electrical conductivity, and mechanical properties. These findings presented in this work demonstrate the promising potential of the carbon aerogel microbeads for such applications.