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Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen

Abstract

This thesis reports an enhanced method to deposit nanoscaled noble metal catalysts (Pt/Ru) uniformly on carbon nanotubes based on wet chemical reduction of anorganic precursors via ethylene glycol. This well-known method is widely used to deposit noble metal catalyst particles on carbon black. Unfortunately, carbon nanotubes tend to agglomerate and therefore form bundles which cannot be penetrated by the precursor. Thus, effectiveness of the substrate is reduced. The new method prevents this by suspending the CNTs in butyl acetate by means of ultrasonic dispersion leading to a homogenous distribution. Because the butyl acetate is almost unpolar, it is nearly immiscible with the water-based ethylene glycol mixture. This problem has been solved by adding liquid Nafion {sup registered} which acts as an emulsifying agent. Thus an emulsion is created by ultrasonic treatment. This results in 30 {mu}m-sized droplets of butyl acetate with a layer of CNTs and Nafion {sup registered}. The large interface to the ethylene glycol phase yields a large surface for homogenous catalyst deposition. The prepared samples showed a narrow size distribution ({+-}0.5 nm) of small noble metal particles with loading up to 50% by weight and an average particle size of 3 nm. They are investigated using XRD,  More>>
Authors:
Publication Date:
Jun 21, 2010
Product Type:
Thesis/Dissertation
Report Number:
ETDE-DE-2402
Resource Relation:
Other Information: TH: Diss. (Dr.-Ing.)
Subject:
30 DIRECT ENERGY CONVERSION; 77 NANOSCIENCE AND NANOTECHNOLOGY; CARBON; NANOTUBES; ELECTRODES; PROTON EXCHANGE MEMBRANE FUEL CELLS; PLATINUM; RUTHENIUM; ELECTROCATALYSTS; SUBSTRATES; FABRICATION
OSTI ID:
21401238
Research Organizations:
Technische Univ. Darmstadt (Germany). Fachbereich 18 - Elektrotechnik und Informationstechnik
Country of Origin:
Germany
Language:
German
Other Identifying Numbers:
TRN: DE11G1740
Availability:
Commercial reproduction prohibited; OSTI as DE21401238
Submitting Site:
DE
Size:
178 pages
Announcement Date:
Mar 15, 2011

Citation Formats

Soehn, Matthias. Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen. Germany: N. p., 2010. Web.
Soehn, Matthias. Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen. Germany.
Soehn, Matthias. 2010. "Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen." Germany.
@misc{etde_21401238,
title = {Carbon nanotubes as electrode substrate material for PEM fuel cells; Kohlenstoff-Nanoroehrchen als Elektrodenmaterial fuer PEM-Brennstoffzellen}
author = {Soehn, Matthias}
abstractNote = {This thesis reports an enhanced method to deposit nanoscaled noble metal catalysts (Pt/Ru) uniformly on carbon nanotubes based on wet chemical reduction of anorganic precursors via ethylene glycol. This well-known method is widely used to deposit noble metal catalyst particles on carbon black. Unfortunately, carbon nanotubes tend to agglomerate and therefore form bundles which cannot be penetrated by the precursor. Thus, effectiveness of the substrate is reduced. The new method prevents this by suspending the CNTs in butyl acetate by means of ultrasonic dispersion leading to a homogenous distribution. Because the butyl acetate is almost unpolar, it is nearly immiscible with the water-based ethylene glycol mixture. This problem has been solved by adding liquid Nafion {sup registered} which acts as an emulsifying agent. Thus an emulsion is created by ultrasonic treatment. This results in 30 {mu}m-sized droplets of butyl acetate with a layer of CNTs and Nafion {sup registered}. The large interface to the ethylene glycol phase yields a large surface for homogenous catalyst deposition. The prepared samples showed a narrow size distribution ({+-}0.5 nm) of small noble metal particles with loading up to 50% by weight and an average particle size of 3 nm. They are investigated using XRD, SEM, TEM, TGA-MS and CV. The added Nafion {sup registered} improves catalyst utilisation by establishing a proton conductive path to the catalyst particles. Furthermore, different manufacturing techniques for the CNT electrodes are evaluated. Thin layer Membrane-Electrode-Assemblies (MEAs) are prepared by the airbrush technique. Electrode thickness, composition and structure as well as membrane thickness is varied and the MEAs are tested in a single-cell hydrogen-oxygen-fed PEM fuel cell. The cells are characterised by cyclic IV curves which are recorded over an extended period of time, showing power densities up to 770mWcm-2 at a platinum loading of 0.3mgcm-2. Additionally, the MEAs are investigated prior to and after fuel cell tests by SEM. (orig.)}
place = {Germany}
year = {2010}
month = {Jun}
}