Carbon Nanotube Sponges, Aerogels, and Hierarchical Composites: Synthesis, Properties, and Energy Applications

Abstract

Carbon nanotube (CNT) aerogels and sponges are macroscopic porous materials with a unique isotropic structure. CNTs make an interconnected 3D scaffold, therefore the resulting aerogels are robust, highly conductive, and flexible, enabling a much broader range of applications than aligned arrays and thin films, especially in energy and environmental areas. A comprehensive overview of the recent progress in isotropic CNT‐based macroscopic structures is provided, including their synthesis methods, structural characteristics, mechanical properties, and deformation mechanism, as well as potential applications in energy and environmental fields. In particular, this study focuses on the CNT sponges developed, which are high‐performance porous materials with many distinct properties such as their versatile deformations and shape recovery. Importantly, the CNT sponges provide a universal platform for designing and manufacturing a variety of hierarchical functional composites by introducing polymers or inorganic guests, thus greatly extend application areas from highly compressible electrodes for supercapacitors and batteries, catalysis, to environmental cleanup. Future research directions and associated challenges in this field are proposed.

Assembling hollow carbon sphere-graphene polylithic aerogels for thermoelectric cells

“…For example, the GHCS-aerogels have showed good mechanical behavior (Young's modulus of 1.8 MPa, yield strength of 0.4 MPa, see Figure S9) and excellent electrical performance (conductivity up to 695 S·m -1 ). The mechanical properties of the resulting aerogels are comparable to those of solution processed graphene aerogels [32], and even much higher than those of electrostatically assembled carbon nanotube aerogels [33]. The electrical conductivity of the resulting aerogel is 6 times higher than that of solution processed graphene aerogels [34], thousand folds higher than that of wetchemistry assembled carbon nanotube aerogels [35].…”

Three-Dimensional Heteroatom-Doped Nanocarbon for Metal-Free Oxygen Reduction Electrocatalysis: A Review

“…Nevertheless, structure optimization of nanocarbon catalysts is one of the main strategies to sufficiently expose and/or activate the catalytic sites. It is noted that low-dimensional nanocarbonsincluding 0D fullerene, 1D carbon nanotubes, and 2D grapheme-usually have low utilization efficiency due to the embedded active sites on the limited surface, which is unfavorable for both mass transport and electron transfer during ORR process [33,52]. However, when fabricated to be a continuous 3D porous structure, the 3D nanocarbon can provide a high surface area with abundant exposed active sites, contributing to good electrocatalytic performance.…”

“…Because of their unique structural characteristics and outstanding physicochemical properties-such as large surface area, high mechanical property, good electrical conductivity, and excellent chemical stability-CNTs have stimulated continuous interest in the field of nanotechnology, especially in environmental and energy areas, in recent decades [52,59]. When heteroatoms are appropriately doped into the carbon matrix of CNTs, enhanced ORR performance can be achieved [8].…”

Versatile Double-Cross-Linking Approach to Transparent, Machinable, Supercompressible, Highly Bendable Aerogel Thermal Superinsulators

“…They are typically prepared by a sol-gel process to obtain hydrogels or alcogels followed by a specific drying process to replace the liquid solvent with air without destroying their delicate nanostructure. Due to their unique porous structures, many kinds of aerogel possess high specific surface area (SSA) and low thermal conductivity, which make them attractive as thermal superinsulators, 1,2 adsorbents, 3,4 catalyst supports, 5 energy storage materials, [6][7][8] etc. Because of their homogeneous nanostructure, some aerogels, especially silica aerogels, are transparent in the visible light wavelengths, which makes them ideal materials as thermally superinsulating windows for efficient energy savings in houses and buildings.…”