EVLN: Automotive Fuel Cell Degradation poses a major challenge

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EVLN: Automotive Fuel Cell Degradation poses a major challenge

brucedp4
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Automotive fcs degrade & need to be replaced in a period of five years

http://www.azom.com/article.aspx?ArticleID=10823
Automotive Fuel Cell Degradation Analysis with In-Situ TEM Electrochemistry
By AZoM.com Staff Writers  Mar 20, 2014  protochips.com

[images  
http://www.azom.com/images/Article_Images/ImageForArticle_10823(1).jpg
Figure 1. Cyclic voltammetry of Pt on a carbon support in situ.

http://www.azom.com/images/Article_Images/ImageForArticle_10823(2).jpg
Figure 2. Carbon support degradation when 1.9V is applied after 0s, 38s, 86s and 260s.
] ...

Introduction

 A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. However, fuel cells are very expensive because of the materials used and also suffer from rapid degradation of charge efficiency.

 These issues pose a major challenge towards their adoption by the automotive industry. This article examines the charge efficiency of fuel cells as well as their ability to charge and discharge at the required performance levels.

Current Fuel Cells

 Present generation of fuel cells tend to degrade within a period of five years and need to be replaced in automotive applications ... The main causes of degradation are believed to be understood, but have previously been unobservable.

Plug-in Hybrid Vehicles

 Plug-in hybrid cars are the opening foray into low emission [plugin] vehicles. The battery, which is presently the most cost effective form for storing energy, will soon be substituted with a more efficient and powerful fuel cell ...

 However, fuel cells have certain drawbacks; they make automobiles cost prohibitive and their rapid degradation makes them impractical half way through the life of the chassis. To this end, government, automakers, and commercial researchers are conducting extensive research to increase this lifespan.

Degradation Mechanisms

 By understanding how the degradation mechanisms progress on the nanoscale, it may be possible to provide a suitable solution to boost the lifetime of fuel cells.

 David Muller’s research group at Cornell University used Protochips’ Poseidon 500 system within an FEI Titan transmission electron microscope (TEM) to image the degradation mechanisms as they occurred.

 During the entire process, the researchers collected quantifiable analytical data with visual observations.

 Earlier, degradation was thought to be an effect of Ostwald ripening, where larger nanoparticles take atoms from smaller nanoparticles. Moreover, it was assumed that coalescence contributed to the remainder of the degradation.

 Although difficult to model, coalescence can be easily observed within a TEM. Through observation, it was ascertained that both coalescence and Ostwald ripening have an equal effect on fuel cell degradation.

 Additionally, both mechanisms exhibit a cooperative effect that leads to coarsening within the cell. Owing to the cooperative nature of the mechanisms, a strategy was adopted to reduce coalescence, and this in turn will also reduce Ostwald ripening.

 Figure 1 shows the cyclic voltammetry of Pt on a carbon support in situ, and Figure 2 shows carbon support degradation when 1.9V is applied after 0s, 38s, 86s and 260s.

 With the help of the Poseidon 500, Dr. Mueller confirmed that he could bring down the degradation mechanisms by a reduction in the loading of particles on the catalyst. Such spatial distributions reduced coalescence by allowing particles to move a longer distance prior to colliding with another particle.

Conclusion
 ... continued and extensive research into their degradation mechanisms is important for commercial applications ...
About Protochips ... protochips.com ... This information has been sourced, reviewed and adapted from materials provided by Protochips ...
[© azom.com]




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