Fuel cells

Gas2Power, automotive, catalysis, zero-polution power generation

The developments in the field of electromobility require new concepts for the generation and storage of electrical energy. Compared to common battery storage systems, fuel cells are an alternative to power generation. Fuel cells convert chemical energy into electrical energy by the reaction between hydrogen and oxygen (from air), so that electric vehicles can also be electrically mobile without a heavy battery and long charging processes.

For the conversion of the reaction energy into electrical energy, the reaction gases must be separated by membranes in the fuel cell. In so-called solid polymer fuel cells (SPFC or Proton Exchange Membrane Fuel Cells, PEMFCs) polymer-based membranes serve as the electrolyte, i.e. as a transport medium for catalytically generated protons. Even slight impurities can lead to a failure of the membranes and thus of the fuel cell, as the following example from our daily analysis shows:

Fuel Cell - Brennstoffzelle

Failure of an electrolyte membrane

Root cause investigation with XPS

In experiments to optimize SPFCs, a sulfonated polyether ether ketone (sPEEK) was identified as a particularly suitable membrane. At the scale up from laboratory to minibatch production, however, the electrolytic properties of the sPEEK membrane used proved to be inadequate. With the help of XPS, the reason for the lack of conductivity of the electrolyte membrane used in the minibatch was to be determined. For this purpose, a comparison of functional membranes of laboratory production (reference) was performed with failing parts from the minibatch production.

The analysis of the C 1s signals of an sPEEK reference and the membrane showed significant differences in the peak shapes, which indicated a contamination of the surfaces. Further investigation revealed that this contamination was polyethylene terephthalate (PET). As shown by the figure of the C 1s signals of all polymer samples, PET can be clearly distinguished from sPEEK by the COO signal (C5). From the quantitative analysis of the XPS data of the membrane a PET coverage of the surface of 10% could be derived. The origin of the PET contamination was identified as a PET carrier film used in the membrane production. By changing the material of the carrier film, the contamination problem could be solved.

 

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