Relationship between structure and electrochemical properties of direct methanol fuel cell anodes

Reduction of the high amount of expensive noble metals in the catalyst layers of direct methanol fuel cells (DMFC) is one of the most important prerequisites for a commercial application of the DMFC. The high catalyst loading of about 3-4 mg/cm² in both electrodes is today necessary because of poor electrode kinetics and permeation of methanol from the anode to the cathode. To overcome these problems, the following goals have to be reached:-development of a chemically and mechanically stable proton conducting membrane with sufficient proton conductivity and low permeation rate of water and methanol-development of stable anode and cathode catalysts with a higher catalytic activity to accelerate kinetics on both electrodes -development of improved electrode structures with respect to active surface, electrical conductivity and mass transport within the pore system.The first two goals require development of new materials. Despite the fact, that big efforts were made in this field since decades, fluorinated polymers like Nafion as a membrane material and platinum based catalysts are still state of the art. The problem is to find materials which fulfill a couple of physico-chemical properties. The development of improved electrode structures is also important, because the structural properties are playing a significant role in the performance of fuel cells. Moreover, a change of the electrode structure is a straight forward approach, because it can be reached by varying the composition and the preparation parameters of the electrodes. When this work started, very little information was existing about the structure and properties of DMFC anodes. Therefore, this work is dedicated to the structure / properties relationship of DMFC anode catalyst layers. More precisely, thin catalyst layers consisting of platinum ruthenium black catalyst and Nafion were object of the investigations. Thin catalyst layers based on Pt/Ru black with a thickness of several micrometer have the following advantages in comparison with about tenfold thicker carbon supported catalyst layers:-the catalyst is concentrated in the electrochemically active zone nearby the inonomer membrane, which means a higher activity of the catalyst -the diffusion length is lower and thus the mass transport is improved -the electrical conductivity is higher.The main task was to study the influence of the composition, catalyst loading and preparation processing parameters on the structural and physico-chemical properties and the performance of DMFC anode catalyst layers. From the relationship of structure and properties, valuable information about future development of improved anode structures with lower catalyst loadings and higher performance should be obtained. The present work is part of a research project funded by the Deutsche Forschungsgemeinschaft (DFG) within the frame of the DFG Schwerpunktprogramm ‘Neuartige Schichtstrukturen für Brennstoffzellen’ (‘Novel layer structures for fuel cells’).

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Havránek, Ales

Contributors dc:contributor

• Stolten, Detlef

• info:eu-repo/classification/ddc/530
• Brennstoffzelle
• Methanolzelle
• Katalysator
• Nafion
• Porosität
• Elektrische Leitfähigkeit
• Leitfähigkeit
• Physik
• ungeträgertes Katalysatorschicht
• Dünnschicht
• Hydrophobie
• Protonenleitfähigkeit
• DMFC
• unsupported catalyst layer
• thin layer
• protonic conductivity

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123249%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61600