Non-destructive functionalisation for atomic layer deposition of metal oxides on carbon nanotubes: effect of linking agents and defects

Abstract

The hybridisation of metal oxides and nanocarbons has created a promising new class of functional materials for environmental and sustainable energy applications. The performance of such hybrids can be further improved by rationally designing interfaces and morphologies. Atomic layer deposition (ALD) is among the most powerful techniques for the controlled deposition of inorganic compounds, due to its ability to form conformal coatings on porous substrates at low temperatures with high surface sensitivity and atomic control of film thickness. The hydrophobic nature of the nanocarbon surface has so far limited the applicability of ALD on CNTs. Herein we investigate the role of structural defects in CNTs, both intrinsic and induced by acid treatment, on coverage, uniformity and crystallinity of ZnO coatings. Furthermore, we demonstrate the potential of small aromatic molecules, including benzyl alcohol (BA), naphthalene carboxylic acid (NA) and pyrene carboxylic acid (PCA), as active nucleation sites and linking agents. Importantly, only PCA exhibits sufficiently strong interactions with the pristine CNT surface to withstand desorption under reaction conditions. Thus, PCA enables a versatile and non-destructive alternative route for the deposition of highly uniform metal oxide coatings onto pristine CNTs via ALD over a wide temperature range and without the typical surface corrosion induced by covalent functionalisation. Importantly, preliminary tests demonstrated that the improved morphology obtained with PCA has indeed considerably increased the hybrid's photocatalytic activity towards hydrogen evolution via sacrificial water splitting. The concept demonstrated in this work is transferable to a wide range of other inorganic compounds including metal oxides, metal (oxy)nitrides and metal chalcogenides on a variety of nanocarbons.

Highly permeable and robust membranes assembled from block-copolymer-functionalized carbon nanotubes

“…As has been widely reported before, CNTs display a hydrophobic property due to its inert surface, [29] which might cause poor permeability for the fabrication of separation 19 membranes. To investigate the surface hydrophilicity of the membrane, contact angles were measured on the composite membranes before and crosslinking.…”

Density Functional Theory and Atomic Force Microscopy Study of Oleate Functioned on Siderite Surface

“…AFM is practical for measuring the surface properties such as morphology and the mechanical properties of many materials at the nanoscale level [19][20][21], and the technique has become viable to study soft matter especially polymers [22][23][24][25]. Height imaging is a widely used application of AFM in the scientific area, which can be utilized to analyze the morphologies of characterized nano-materials, such as nano-particles [26], nano-tubes [27], and nano-sheets [28]. Over the past three decades, several publications were reported to employ AFM method in siderite formation research.…”

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage

“…By proper surface functionalization (such as by conjugating –NO 2 or –OH groups) on carbon surface, rather uniformly deposited ALD materials are obtained. The substrate surface properties have also shown great influence on electrochemical behavior and other functional behavior such as catalysis and sensing,115, 117 and therefore they impact on the device performance. To develop a proper continuous layer of ALD TiO 2 on graphene, ALD Al 2 O 3 has to be deposited first on graphene as a buffer layer, otherwise only isolated nanoparticles of TiO 2 are formed with little capacity 118…”