Which phenomenon limits high performance proton exchange membrane's (PEM's) fuel cell ability to operate well below 0°C?

💡 Explanation

Ionomer phase separation constricts PEM pores because water freezes and segregates the hydrophobic and hydrophilic regions, resulting in a loss of proton conductivity due to reduced reactant transport. Therefore separation limits pore availibility, rather than ruptures from hydrogen embrittlement alone.

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