Carbon aerogel evolution: Allotrope, graphene-inspired, and 3D-printed aerogels
- PDF / 1,177,178 Bytes
- 20 Pages / 584.957 x 782.986 pts Page_size
- 35 Downloads / 215 Views
Carbon aerogels (CAs) are a unique class of high surface area materials derived by sol–gel chemistry. Their high mass-specific surface area and electrical conductivity, environmental compatibility, and chemical inertness make them very promising materials for many applications, such as energy storage, catalysis, sorbents, and desalination. Since the first CAs were made via pyrolysis of resorcinol–formaldehyde (RF)-based organic aerogels in the late 1980s, the field has really grown. Recently, in addition to RF-derived amorphous CAs, several other carbon allotropes have been realized in aerogel form: carbon nanotubes (CNTs), graphene, graphite, and diamond. Furthermore, the popularity of graphene aerogels has inspired research into aerogels made of a host of graphene analog materials (e.g., boron nitride, transition metal dichalcogenides, etc.), with potential for an even wider array of applications. Finally, the development of threedimensional-printed aerogels provides the potential for CAs to have an even broader impact on energy-related technologies. Here, we will present recent work covering the novel synthesis of RF-derived, CNT, graphene, graphite, diamond, and graphene analog aerogels.
I. INTRODUCTION
Aerogels cover a class of solid materials distinguished by their extreme low density and ultrafine, open pore structure. Initially synthesized as a wet gel, aerogels are created by replacing the liquid phase of the wet gel with gas, which results in a dry porous solid. As the pore structure is minimally perturbed during this process, it is not uncommon for aerogels to consist of greater than 95% porosity, with pores that average less than 100 nm. These features alone give aerogels in general some very unique properties, such as large accessible surface areas and extremely low thermal conductance. In fact, the first metal-oxide aerogels prepared by Kistler et al. targeted applications in catalysis1 and thermal insulation2 to take advantage of these novel properties. Aerogel research has continued to grow since Kistler et al. prepared the first aerogels in the 1930s. For the first few decades, though new synthesis routes were reported,3,4 the composition of aerogels was limited to metal oxides. However, in the past 30 years, there has been a collective push to not only develop new methods5 to produce traditional metal oxides but also to expand the variety of materials that aerogels cover. Some notable examples of these new aerogels include reports of organic aerogels,6 carbons,7–10 conducting oxides,11 Contributing Editor: Paolo Colombo a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.411
chalcogenides,12 metals,13–15 and various two-dimensional (2D) materials.16–18 A major driver for realizing aerogels from a wider materials set is the potential to unlock novel properties that these materials only exhibit as aerogels. Carbon aerogels (CAs), in particular, possess a unique combination of ultralow density, large surface area, high electrical conductivity, thermal and chemica
Data Loading...
