Carbon nanotube (CNT) sponges are made from interconnected carbon nanotubes, in which nanotubes are self-assembled into a three-dimensionally interconnected framework. These carbon nanotubes are tiny, strong and hollow cylinders that are about 30-50 nanometers across and tens to hundreds of micrometers long. CNT sponges are highly porous, which leaves a lot of space to absorb oil and solvents. In addition, they are very light, hydrophobic in pristine form, and can be elastically and reversibly deformed into any shape.
Fig 1 a) Photo of a bulk CNT sponge. b) SEM image of the inner part of the sponge.
(Z. Q. Lin et al., Adv. Energy Mater., 2016, 1600554)
CNT sponges are novel materials possessing nanoscale structures, which have excellent properties that integrate the merits of aerogels with their high surface area, and conventional soft materials with their robustness and flexibility. CNT sponges were prepared by chemical vapor deposition, using ferrocene and dichlorobenzene as the catalyst precursor and carbon source. Most importantly, the light-weight, high porosity, and large surface area of CNT-based materials make them a promising candidate for environmental applications such as sorption, filtration and separation.
Fig 2 Schematic of the pore structure in CNT sponges
Environmental cleanup: CNT sponges possess a freestanding stable structure, high surface area, low density, super hydrophobic surface, as well as chemical stability. A combination of such distinct characteristics makes these CNT sponges very promising for environmental applications such as water purification and oil spill cleanup. These sponges can float on water surfaces and absorb large-area spreading oil films.
Catalyst: CNT sponges are ideal materials for catalysis, acting either as catalyst themselves or as skeletons for loading selected catalysts. The high specific surface area of CNT sponges offers abundant active sites and the highly conductive CNT networks which can boost reaction kinetics. In addition to this, their mechanical and chemical stability lead to longer cycle life of catalysts.
Electrochemical Energy Storage: Bulk CNT sponges with high porosity and good mechanical stability can be used as 3D porous electrodes for Li-Ion Batteries. CNT sponge offers a conductive network and high surface area, which are always combined with high energy density and chemical-activity materials to make composite electrodes to boost battery performance.