Cell Structure Flashcards
What is the structure of a single cell assembly?
Endplate, current collector, flowfield, sealing gasket, MEA, then mirrored apart from MEA.
What are the properties of the PEM?
Hydrophobic and hydrophilic so that it can absorb and repel water.
What does a low humidity cause to the PEM?
No H+ skipping - low ionic conductivity.
What does a high humidity cause to the PEM?
More H+ movement - high ionic conductivity.
What is the role of the CL?
Increase reaction rate and power density.
What materials is the CL made of?
Platinum dispersed in carbon.
Which electrode uses the most platinum and why?
The cathode, to improve the net reaction rate, since the cathode is the limiting factor.
What is the GDL made from?
Carbon, coated with PTFE
What are the three roles of the GDL?
Transport reactant gases from high to low concentration.
Remove product water.
Transport electrons.
What physical properties must the GDL have?
Porous, flexible and compressible, low resistance.
What are the three layers of the structure of the MEA?
Anode - membrane - cathode.
What are the three layers of the electrodes?
GDL - MPL - CL.
Which layer within the electrodes contacts the membrane?
The CL.
What is the role of the MPL?
Bridges gap and makes contact between GDL and CL.
Improves water wicking.
