Carbon Nanotubes and Nanohorn Hybrid Composite Buckypaper as Microporous Layer for Proton Exchange Membrane Fuel Cell

In the present work, carbon nanotubes (CNT) and CNT‐carbon nanohorns (CNH) (0, 30, 50, 70 and 100 wt.% CNH) composite Buckypapers (BPs) were fabricated using vacuum filtration technique. Structure and property relation of composite BPs were studied using scanning electron microscope, four probe technique, BET surface area and contact angle measurements. Properties such as electrical conductivity, hydrophobic nature and microstructure of CNT‐30 wt.% CNH composite BP are superior to other composite BP. Hence, CNT‐30 wt.% CNH composite BP is chosen as a microporous layer (MPL) for PEMFCs and tested in fuel cell testing fixture. Polarization studies reveal that the cells performance with composite BPs is comparable with SGL‐MPL based cell. Hydrogen pumping and polarization studies of the cells confirms that composite BPs act as a good MPL at anode as well as cathode at 0.4 to 0.8 V. Hence, CNT‐CNH composite BPs are potential candidates for PEMFC applications.     

Development of a self-supported single-wall carbon nanotube-based gas diffusion electrode with spatially well-defined reaction and diffusion layers

This work reports on the development of a solvent-free method for the fabrication of a self-supported single-wall carbon nanotubes electrode, which is based on successive sedimentation of both SWCNT/surfactant and PtRu-SWCNT/surfactant suspensions followed by a thermal treatment at 130 °C. The as-prepared self-supported electrode showed sufficient mechanical strength for half-cell investigation and membrane-electrodes assembly fabrication. By using a Pt catalyst loading of 1 mg cm⁻², the overall thickness of the gas diffusion electrode reached 95 μm. Its electrochemical activity towards methanol oxidation was investigated by means of cyclic voltammetry and current-voltage polarisation measurements under half-cell and direct methanol fuel cell conditions.     

Study of the mechanical,electrical and morphological properties of PU/MWCNT composites obtained by two different processing routes

A comparative study of the influence of processing route on polyurethanes (PUs)/multiwalled carbon nanotube (MWCNT) composites mechanical and electrical properties and also morphology was undergone employing two differentiated processing methods, solvent casting and buckypaper infiltration, for producing PU composites with low, medium and high mass fractions of acid treated MWCNT, and with no covalent linkages between the matrix and the nanotubes. As for example, with a MWCNT mass fraction of ∼18 wt.% the second method produced stiffer (270 MPa), lighter (948 kg m⁻³) and more electrically conductive (1.8 S cm⁻¹) composite while the first one gave softer (111 MPa) and more ductile (141%) materials. These properties differences are related to the different PU/MWCNT dispositions obtained through each synthesis route. Nanotubes percolating concentration is found to be crucial on composite properties evolution and a preferential interaction of MWCNT with PU hard segments is observed for solvent cast composites.     

A Review on Properties and Fabrication Techniques of Polymer/Carbon Nanotube Composites and Polymer Intercalated Buckypapers

This review is a comprehensive source for synthesis, functionalization, and physical properties of polymer/carbon nanotube nanocomposites. The effectiveness of processing methods for carbon nanotube reinforcement in matrix for proper dispersion and appropriate interfacial adhesion is discussed. The novelty of polymer/carbon nanotube buckypaper fabrication with preformed networks through microfiltration of nanotube suspension has also been discussed. Moreover, preparation, properties, and manufacturing proficiencies of buckypaper are reviewed. Different approaches of intertwining buckypaper through infiltration, compression, soaking, and dry transfer have been analyzed. The polymer/carbon nanotube buckypaper obtained by vacuum infiltration has micron-scale bicontinuous morphology and improved thermal properties due to effectual heat transfer within nanotube rich phase.     

Buckypaper-based catalytic electrodes for improving platinum utilization and PEMFC's performance

Platinum (Pt) catalytic electrode was developed by using carbon nanotube films (buckypaper) as supporting medium and electrodeposition method to deposit Pt catalyst. Buckypapers are free-standing thin films consisting of single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs) and/or carbon nanofibers (CNFs) held together by van der Waals forces without any chemical binders. Special mixed buckypapers was developed by layered microstructures with a dense and high-conducting SWNT networks at the surface, as well as large porous structures of CNF networks as back supports. This unique microstructure can lead to improve Pt catalyst accessibility and mass exchange properties. Pt particles of about 6 nm were uniformly deposited in porous buckypapers. A promising electrochemical surface area of ∼40 m²/g was obtained from these electrodes. A Pt utilization as low as 0.28 g_Pt/kW was achieved for the cathode electrode at 80 °C. Pt utilization efficiency can be further improved by optimization of the electrodeposition condition in order to reduce the Pt particle size.     

Influence of geometries of multi-walled carbon nanotubes on the pore structures of Buckypaper

Influence of geometries, i.e. lengths and diameters, of multi-walled carbon nanotubes (MWCNTs) on pore sizes and distributions as well as resin impregnation quality of Buckypaper was studied. Three kinds of MWCNTs with different lengths and diameters were used to fabricate Buckypapers by the process of vacuum assisted filtration. Scanning electron microscopy (SEM) and N₂ adsorption results show that the Buckypaper made of MWCNTs with longer lengths and thinner diameters has the smallest mean pore diameters and best pore size distribution. The results also show that MWCNTs with larger diameters are more inclined to form pore structures with larger pore sizes, and MWCNTs with shorter lengths are more inclined to form pore structures with much wider pore size distribution. Microstructure characterization of the Buckypaper/epoxy composites also exhibited phenomenon of the same rules.     

Core–shell tin-multi walled carbon nanotube composite anodes for lithium ion batteries

Carbon nanotube papers were produced from Multi wall carbon nanotubes (MWCNTs). Tin deposition was conducted via RF magnetron sputtering technique on the MWCNT papers to produce tin-MWCNT composite anodes. The effect of different sputtering power on the electrochemical performance of anodes was investigated. Galvanostatic charge/discharge technique was employed to determine the cyclic performance of the anode electrodes. Results showed that improvement on cyclic performance of tin anodes was achieved with novel composite tin-MWCNT composite anode structures.     

Influence of lengths of millimeter-scale single-walled carbon nanotube on electrical and mechanical properties of buckypaper

The electrical conductivity and mechanical strength of carbon nanotube (CNT) buckypaper comprised of millimeter-scale long single-walled CNT (SWCNT) was markedly improved by the use of longer SWCNTs. A series of buckypapers, fabricated from SWCNT forests of varying heights (350, 700, 1,500 μm), showed that both the electrical conductivity (19 to 45 S/cm) and tensile strength (27 to 52 MPa) doubled. These improvements were due to improved transfer of electron and load through a reduced number of junctions for longer SWCNTs. Interestingly, no effects of forest height on the thermal diffusivity of SWCNT buckypapers were observed. Further, these findings provide evidence that the actual SWCNT length in forests is similar to the height.     

Research Advancement Towards Polymer/Nanodiamond Composite in Buckypaper: A Review

Recent technological advancements in polymeric buckypaper materials have brought spotlight on polymer/nanodiamond buckypaper. This review is designed as systematic and comprehensive source of information and research on nanodiamond, polymer/nanodiamond nanocomposite and buckypaper, and technological advancement in this field. Structure, properties, and manufacturing techniques of polymer/nanodiamond buckypaper are reviewed. Because of outstanding physical properties, polymer-based buckypaper has been used as potential contenders in nanofilter, supercapacitor, fuel cell, electrical components, and biomedical devices. However, property dependence in relation to chemical structure is not fully identified in the literature. To find out further technical suitability of polymer/nanodiamond materials are still among predominant research challenges.     

Fabrication and impedance studies of DMFC anode incorporated with CNT-supported high-metal-content electrocatalyst

In this study, the fabrication of a direct methanol fuel cell (DMFC) anode with the incorporation of a multiwalled carbon nanotube (CNT)-supported high-metal-content Pt/Ru electrocatalyst, i.e., 40 wt%Pt-20 wt%Ru/CNT, using a novel approach and the resultant DMFC performances were investigated. Employing a vacuum filtration method, we were able to successfully fabricate the DMFC anode with a good electrode structure using an in-house prepared Pt-Ru/CNT electrocatalyst. The catalyst layer was formed directly on a Teflon-treated carbon cloth having a buckypaper texture with a catalyst loading of 4.0 mg cm⁻². From single-cell tests, excellent cell performances were obtained. At 80 °C, the power density was found to be as high as >100 mW cm⁻². This can be attributed to a thinner catalyst layer formed with a more efficient utilization of the catalyst than that using a low-metal-content counterpart, i.e., 20 wt%Pt-10 wt%Ru/CNT, as reported in an earlier study. However, the Nafion^® ionomer content in the catalyst layer played a key role in the anode fabrication to obtain a good cell performance. In addition, the electrochemical impedance spectroscopy (EIS) with a constant phase element (CPE)-based equivalent-circuit model was employed to analyze the fabricated anode. It distinctively revealed some specific characteristics in the resistances and the interface properties. Overall, the obtained impedance results are somewhat different from those of a conventional DMFC anode with the catalyst layer coated onto a porous gas diffusion layer (GDL) on a carbon backing material. Based on the experimental results and the impedance analyses, the high-metal-content Pt-Ru/CNT catalyst was found to be much more favorable and suitable for use as a DMFC anode catalyst.