Electrochemical Performance Measurements of PBI-Based High-Temperature PEMFCs

Table 4

Warburg impedance for PBI-based MEAs at 180^∘𝐶.

PBI content (wt.%)	Warburg impedance (R, Ohm-cm^2)	𝑆=𝐿^2/𝐷 (s)
1	2.19	0.023
5	1.84	0.017
10	2.83	0.030
20	3.85	3E-04
30	6.25	3E-07

S is a time constant; L is the effective diffusion thickness, and D the effective diffusion coefficient.