Proton Exchange Membrane Fuel Cells with Carbon Nanotube Based Electrodes

AuBuchon

Applied Physics Letters

et al. 2006

It is shown that unidirectionally aligned carbon nanotubes can be grown on electrically conductive network of carbon microfibers via control of buffer layer material and applied electric field during dc plasma chemical vapor deposition growth. Ni catalyst deposition on carbon microfiber produces relatively poorly aligned nanotubes with significantly varying diameters and lengths obtained. The insertion of Ti 5 nm thick underlayer between Ni catalyst layer and C microfiber substrate significantly alters the morphology of nanotubes, resulting in much better aligned, finer diameter, and longer array of nanotubes. This beneficial effect is attributed to the reduced reaction between Ni and carbon paper, as well as prevention of plasma etching of carbon paper by inserting a Ti buffer layer. Such a unidirectionally aligned nanotube structure on an open-pore conductive substrate structure may conveniently be utilized as a high-surface-area base electrodes for fuel cells, batteries, and other electrochemical and catalytic reactions. Carbon nanotubes ͑CNTs͒ have emerged as a new and attractive class of materials with unique electrical, mechanical, and various physical and chemical properties. [1][2][3] Potential applications include nanoelectronic devices, 4-7 catalyst supports, 8 storage materials for hydrogen and other gases, 9,10 and probe tips for atomic force microscope ͑AFM͒. 2,11 While there have been a very large number of publications on nanotube growth and their applications, engineering the shape of CNTs is an important issue for successful applications of nanotubes. Aligned and well separated CNT morphology is important for many potential applications, where a high electric-field concentration is needed as in field emission applications, and where a large surface area is desirable as in catalytic reactions, such as fuel cell or battery applications.The growth of CNTs by dc plasma-enhanced chemical vapor deposition ͑CVD͒ involves many processing parameters, such as bias field, plasma power, temperature, chamber pressure, and feed gas composition. In general, the diameter and distribution of CNTs synthesized by CVD processing are dependent on the morphology of catalyst particles or layer. The shape of CNTs can be controlled by the applied bias voltage, the nature of catalyst and buffer layer deposition as well as the composition of plasma in a dc plasma-enhanced CVD process. 12,13 The growth direction of the nanotubes can be controlled by the electrical field related to either applied bias or plasma induced bias, which is often perpendicular to the substrate surface. More recently, multiple sharp bending of CNTs to produce a zig-zag morphology has also been demonstrated by repeatedly altering the applied field directions. 14 Such an alignment of CNTs has been demonstrated mostly on flat surfaces, and there have been few reports on aligned CNT growth on a fiber-configured substrate.It is well known that CNT nucleation and growth occurs mostly on semiconductive Si substrate as well as electrically insulating ceram...

mentioning

confidence: 98%

Growth of aligned carbon nanotubes on carbon microfibers by dc plasma-enhanced chemical vapor deposition

AuBuchon

Applied Physics Letters

et al. 2006

AIP Conference Proceedings

“…However, it is already known that carbon black undergo electrochemical oxidation to surface oxides, and eventually to CO 2 at the cathode of a fuel cell, where it is subject to high acidity, high potential, high humidity, and high temperature [7]. To overcome the limitation of carbon black, more stable support material, carbon nanotube (CNT) has been being an attractive candidate for recent years to improve the PEMFC performance because of its high electrical conductivity, high aspect ratio, and high transport capability [8]. The requirements for a durable carbon support are to provide a strong interaction between support and catalytic metals and to exhibit a high corrosion resistance at highly oxidizing potentials [9].…”

Section: Introductionmentioning

confidence: 99%

Polarization losses under dynamic load cycle using multiwall carbon nanotube supported Pt catalyst in PEM fuel cell

Irmawati¹,

Indriyati²,

Chaldun³

et al. 2016

Erratum: "Magnetocaloric effect in La 0.7 Ca 0.3 MnO 3 nanotube arrays with broad working temperature span" [J. Appl. Phys. 117, 104304 (2016) Abstract. Durability is one of the most important issues that are still being a hindrance for commercialization of polymer electrolyte membrane fuel cell (PEMFC). In this study, the degradation of PEMFC using multiwall carbon nanotube supported Pt catalyst (Pt/CNT) was investigated under dynamic load cycle procedure. The degradation was characterized by current density-voltage curves, cross-sectional scanning electron microscopy (SEM) images, and Fourier transforms infrared spectroscopy (FTIR) spectra. The load-cycle procedure was carried out for 50 cycles, where one cycle consisted of three steps (OCV-load current-constant voltage). An analysis of cell overpotentials indicated that the predominant source of performance degradation was due to ohmic losses, especially significant increase in the area specific resistance (R a ). After 50 cycles, R a was calculated three times higher than that before durability test, from 0.67 to 1.74 Ωcm 2 . Based on the results from SEM images and FTIR spectra, there was no evidence of membrane degradation or thinning. Noticeable degradation was only observed from the increase in the interface gap between membrane, catalyst layer, and gas diffusion layer.

“…To overcome this issue, self-supported 1D NWs is a favorable solution for smooth electron transfer and to avoid structural collapse [23][24][25]. Recently, we have developed a novel 'electrochemical micelle assembly' soft-templating method which is a facile and effective route to obtain mesoporous metals with controlled pore sizes [18,26,27].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Synthesis of Mesoporous Pt Nanowires with Highly Electrocatalytic Activity toward Methanol Oxidation Reaction

Malgras

Alshehri

et al. 2015

Electrochimica Acta

. (2015). Electrochemical synthesis of mesoporous Pt nanowires with highly electrocatalytic activity toward methanol oxidation reaction. Electrochimica Acta, 183 107-111.Electrochemical synthesis of mesoporous Pt nanowires with highly electrocatalytic activity toward methanol oxidation reaction AbstractSelf-supported one-dimensional (1D) mesoporous Pt nanowires (NWs) are prepared by confining micelle assembly in channels of a polycarbonate (PC) membrane. The obtained mesoporous Pt NWs show very high electrochemical activity and excellent durability as catalysts for methanol oxidation reaction (MOR) in comparison with the commercially available Pt black (PtB) catalyst. This work demonstrates that an appropriate combination of both self-supported 1D shape and mesoporous architecture indeed improve the electrocatalytic performances which is critical for further implementation and practical applications. Abstract: Self-supported one-dimensional (1D) mesoporous Pt nanowires (NWs) are prepared by utilizing micelle assembly in channels of a polycarbonate (PC) membrane. The obtained mesoporous Pt NWs show very high electrochemical activity and excellent durability as catalysts for methanol oxidation reaction (MOR), in comparison with the commercially available Pt black (PtB) catalyst. This work demonstrates that nice combination of both self-supported 1D shape and mesoporous architecture indeed improve the performance as electrocatalysts, which is an important finding for considering practical applications.