A study of water adsorption and desorption by a PBI-H_3PO_4 membrane electrode assembly

摘要

Data corresponding to the isotherms for the equilibrium water content of a PolyBenzlmidazole (PBI)-H_3PO_4 High Temperature Membrane Electrode Assembly (HT-MEA) are presented over a range of temperatures from 30℃ to 180℃ The data show values for the ratio of water to acid which range from 4.0 at 70℃ to 0.2 at -160℃ at 30kPa of water vapor pressure. In addition to the equilibrium data, rates of adsorption are shown to have time constants on the order of 500 sand 2500 s at 70℃ and 50℃, respectively. At temperatures above 100℃ the time constants for adsorption are on the order of 100 s. These data allow for the calculation of "acid dilution" in this HT-MEA during low-temperature excursions and start up/shut down.