Temperature-dependent gas accumulation in polymer electrolyte membrane electrolyzer porous transport layers

We investigate the temperature-dependent gas saturation in the porous transport layer (PTL), and the subsequent impact of this gas saturation on the mass transport overpotential of a polymer electrolyte membrane (PEM) electrolyzer. Via in operando neutron imaging of a PEM electrolyzer, we observe that increasing the operating temperature results in a) the reduction of gas saturation in the PTL (particularly near the catalyst layer (CL)-PTL interface) and b) the promotion of uniform gas distributions near the CL-PTL interface. Via two-dimensional computational fluid dynamics modelling of the PEM electrolyzer, we observe that increasing the operating temperature results in a) the reduction of dissolved oxygen concentrations and b) the promotion of uniform dissolved oxygen concentrations near the CL-PTL interface. Therefore, we attribute our observation of lower and more uniform gas saturation to correspondingly lower and more uniform gas evolution rates that would accompany the dissolved oxygen concentrations predicted by our model. Increasing the operating temperature leads to lower mass transport overpotentials, which we attribute to the combined effects of lower and more uniform gas saturations and lower dissolved oxygen concentrations near the CL-PTL interface. Based on this work, we recommend higher operating temperatures for optimal water and oxygen transport in the PTL.