Ultra‐Permeable Single‐Walled Carbon Nanotube Membranes with Exceptional Performance at Scale

Abstract

Enhanced fluid transport in single-walled carbon nanotubes (SWCNTs) promises to enable major advancements in many membrane applications, from efficient water purification to next-generation protective garments. Practical realization of these advancements is hampered by the challenges of fabricating large-area, defect-free membranes containing a high density of open, small diameter SWCNT pores. Here, large-scale (≈60 cm 2) nanocomposite membranes comprising of an ultrahigh density (1.89 × 10 12 tubes cm −2) of 1.7 nm SWCNTs as sole transport pathways are demonstrated. Complete opening of all conducting nanotubes in the composite enables unprecedented accuracy in quantifying the enhancement of pressure-driven transport for both gases (>290× Knudsen prediction) and liquids (6100× no-slip Hagen-Poiseuille prediction). Achieved water permeances (>200 L m −2 h −1 bar −1) greatly exceed those of state-of-the-art commercial nano-and ultrafiltration membranes of similar pore size. Fabricated membranes reject nanometer-sized molecules, permit fractionation of dyes from concentrated salt solutions, and exhibit excellent chemical resistance. Altogether, these SWCNT membranes offer new opportunities for energy-efficient nano-and ultrafiltration processes in chemically demanding environments. Carbon nanotubes (CNTs) have garnered sustained interest in many areas of material science due to their outstanding thermal, mechanical, electrical, and fluidic properties and have enabled advancements in a variety of functional materials and technologies. [1,2] In separation applications, CNTs are interesting membrane building blocks as their unique transport properties lead to exceptionally large flow rates compared to conventional porous materials with commensurate pore sizes.

Carbon Nanotube Membranes in Water Treatment Applications

“…A scale-up study was conducted by Jue et al, who fabricated large-scale area (60 cm 2 ) VA-CNT membranes with high density of open, small diameter SWCNT pores. [21] The resulting membranes showed excellent water permeances that exceeded those of state-of-the-art commercial nano-and ultrafiltration membranes with similar pore diameters, and permitted fractionation of dyes from concentrated salt solutions.…”

“…In fact, permeability depends on several aspects such as pore density, CNT size, and the number of CNT walls. [21,47,50] Permeability and selectivity of the VA-CNT membranes can also be controlled via tip/sidewall functionalization with suitable chemical groups. [12,51,52] Practical applications of VA-CNTs are often limited by their surface properties; however, the surface can be chemically modified in order to meet the specificity of each particular application.…”

“…[20] Furthermore, CNTs with small diameters (SWCNTs) allow the fabrication of highly permeable and very selective high-density membranes through the fabrication of vertically aligned CNT platforms, with water permeances that exceed those of conventional nano-and ultrafiltration membranes. [21] On the contrary, for large-diameter CNTs, the pore size effect is relevant in comparison to the hydrophobic character, and water transport is improved as the number of walls is increased. [20] Selectivity is also affected by the diameter of the CNTs.…”

A review on emerging developments in thermal and moisture management by membrane‐based clothing systems towards personal comfort

“…Fabrication of large-scale (≈60 cm 2 ) membrane composed of SWCNTs with ultrahigh density proved that the next generation protective garments could benefit from incorporating CNTs into the membrane structure. 227 A Chemical stimuli-responsive membrane is fabricated with the potential to be highly breathable in safe environments and protective in chemically pollutant environments. 228 This bistable film selectively impedes organophosphate molecule transport through CNT pores.…”

Stable Organic Passivated Carbon Nanotube–Silicon Solar Cells with an Efficiency of 22%

“…[ 21 ] However, the downside of the approach was the long term stability of the CNT:Nafion composite layer. Although CNTs have excellent stability toward degradation in ambient, humid, hot, or ultraviolet radiation conditions, [ 28 , 29 , 30 , 31 ] the hygroscopic nature of Nafion is known to lead to performance reductions [ 32 ] and must be addressed. Primarily, these issues are related to reductions in the open circuit voltage ( V oc ) from degradation of the Nafion based passivation.…”