Macroscopic Carbon Nanotube‐based 3D Monoliths

Abstract

Carbon nanotubes (CNTs) are one of the most promising carbon allotropes with incredible diverse physicochemical properties, thereby enjoying continuous worldwide attention since their discovery about two decades ago. From the point of view of practical applications, assembling individual CNTs into macroscopic functional and high-performance materials is of paramount importance. For example, multiscaled CNT-based assemblies including 1D fibers, 2D films, and 3D monoliths have been developed. Among all of these, monolithic 3D CNT architectures with porous structures have attracted increasing interest in the last few years. In this form, theoretically all individual CNTs are well connected and fully expose their surfaces. These 3D architectures have huge specific surface areas, hierarchical pores, and interconnected conductive networks, resulting in enhanced mass/electron transport and countless accessible active sites for diverse applications (e.g. catalysis, capacitors, and sorption). More importantly, the monolithic form of 3D CNT assemblies can impart additional application potentials to materials, such as free-standing electrodes, sensors, and recyclable sorbents. However, scaling the properties of individual CNTs to 3D assemblies, improving use of the diverse, structure-dependent properties of CNTs, and increasing the performance-to-cost ratio are great unsolved challenges for their real commercialization. This review aims to provide a comprehensive introduction of this young and energetic field, i.e., CNT-based 3D monoliths, with a focus on the preparation principles, current synthetic methods, and typical applications. Opportunities and challenges in this field are also presented.

Mesoporous binder-free monoliths of few-walled carbon nanotubes by spark plasma sintering

“…This could reflect a partial opening of the CNTs [37]. The present values for S BET and pore size distribution are in line with the values reported for carbon monoliths for non-activated carbon (KOHactivation is known to increase the specific surface area and microporosity) and possible applications could be as oil or gas sorbents [16,[48][49][50]. The porous volume (Vp- Table 2) for 4W1000 (0.899 cm 3 /g) and 4W1100 (0.734 cm 3 /g) is, however, significantly (2-3 times) higher than for the other present monoliths and those reported elsewhere [16,49,50].…”

Recent Development of Advanced Materials with Special Wettability for Selective Oil/Water Separation

“…Carbon nanotube (CNT)-based aerogels/ sponges have proven their effi ciency as superabsorbents for oil/water separation. [92][93][94][95][96][97][98][99][100] For example, Gui et al fabricated CNT sponges that could selectively remove oil fl oating on water. [ 93 ] Due to their light weight, intrinsic hydrophobicity and oleophilicity, the CNT sponge could fl oat on the water surface and automatically drift towards the remaining oil fi lm.…”

Density controlled oil uptake and beyond: from carbon nanotubes to graphene nanoribbon aerogels

“…As shown in Figure 3a, the aerogel density was plotted versus the adsorption capacity of bromobenzene (expressed by the weight gain of aerogels after adsorption) in a wide range. 29 Assuming the bulk density of MWNTs (~2.1 g cm -3 ) was approximately equal to that of GNRs (~2.2 g cm -3 ), 36, 37 the oil uptake capacity was also correlated with aerogel porosity following a similar power function ( Figure S7a). S6), from ~740 wt% for 191 mg cm -3 , to ~27630 wt% for 2.5 mg cm -3 .…”

“…29 For oil uptake, the pore volume of all pores sizes, especially macropores, should be included. 29 For oil uptake, the pore volume of all pores sizes, especially macropores, should be included.…”