Carbon aerogels (CAs) are nano-porous carbons comprising a particularly significant class of carbon nano-materials for a variety of sustainable energy applications. Carbon aerogels are specifically promising in that they possess a tunable, three-dimensional, hierarchical morphology with ultrafine cell size and an electrically conductive framework. They are available as macroscopic, centimeter-sized monolithic materials. Carbon aerogels hold great technological promise for a variety of sustainable energy applications including hydrogen and electrical energy storage, desalination, and electrocatalysis.
Aerogels in general constitute a special class of open-cell foams that exhibits properties such as low mass density, continuous porosity, and high surface area. The CA microstructure typically consists of three-dimensional networks of inter-connected nanometer-sized primary particles. Sol-gel methods are used to prepare the materials where the liquid in the gel is removed, leaving the solid matrix intact. In essence, the liquid in the gel is replaced with a gas. This transforms the organic aerogel precursor into a porous carbon network comprised of both amorphous and microcrystalline regions. These materials are mass-producible.
As a result, CAs combine the properties of high surface area, electrical conductivity, chemical stability, and environmental compatibility in one material. When doped or modified with other materials to tune their properties, CAs are specifically useful as carbon nanotube-carbon aerogel (double- and single-walled carbon nanotubes); metal oxide — carbon aerogel or metal carbonitride — carbon aerogel; and as polymer composites of these materials.
The CAs are excellent thermal insulators because their gaseous components greatly reduce heat transfer by conduction, convection, and radiation.