Table 1.

Difference between cation and anion exchange membrane.

IEM	CEM	AEM
Counter ion	H+ conductive	OH− conductive
Ion-exchange group	-SO3−; -PO4−; -CO2−	Quaternary ammonium cation, 1-methyl pyridinium
Features	High ionic conductivity, excellent ionomer solution	Non-noble metal catalyst can be used. Oxygen reduction reaction and methanol oxidation reaction are more facile.
Issues	High-cost materials, fuel crossover, chemical, and mechanical stability, practical lifetime	Low ionic conductivity, low thermostability, influence of CO2, durability, chemical, and mechanical stability