Esterification as a diagnostic tool to predict proton conductivity affected by impurities on Nafion components for proton exchange membrane fuel cells

Effect of ammonium ion distribution on Nafion® conductivity

“…It can be seen that the conductivity of a non-uniformly ammonium ion-poisoned membrane is different from that of a uniformly poisoned membrane, even though the membranes contain the same amounts of ammonium ions (overall values of y NH 4 + being the same). This is true over a wide range of conditions (30-100%RH at 80 • C) [16]. This observation implies that the distribution of foreign cationic ions (i.e., NH 4 + in this case) could have a significant effect on Nafion con- ductivity.…”

“…This observation suggests that a conductivity model taking into account the non-homogeneity of ammonium ion concentration profile within a membrane or a catalyst layer would yield a more accurate prediction for a contaminated PEMFC performance. If the concentration profile is known, the overall conductivity ( overall ) of a Nafion membrane [16] and that of a Nafion's catalyst layer [20] can be calculated as follows:…”

“…This observation implies that the distribution of foreign cationic ions (i.e., NH 4 + in this case) could have a significant effect on Nafion con- ductivity. Especially, at low humidities (<50%RH) and moderate ammonium ion concentrations (0.2 < y NH 4 + < 0.8), the conductivity of the non-uniformly poisoned membrane can be greater by 1.04-4 times than that of the uniformly poisoned membrane [16]. However, the ammonium ion distribution was not able to be quantitatively determined during those studies.…”

Ammonia as a Hydrogen Source for Fuel Cells: A Review

“…Hongsirikarn et al [83][84] performed further studies on the effects of ammonia on Nafion, measuring the membrane conductivity in the liquid and gas phases. They prepared their membranes using HCl and NH4Cl to simulate the desired concentrations of H + and NH4 + in the membrane.…”

An experimental approach to investigate the transport of ammonia as a fuel contaminant in proton exchange membrane fuel cells

“…Furthermore, they showed that N 2 and NO could be generated through an NH 3 oxidation reaction by using differential electrochemical mass spectrometry [7]. Hongsirikarn et al [9,10] investigated the effect of NH 3 and NH 4 þ in the aqueous and vapor phases on the conductivity of a Nafion ® membrane, and concluded that the operation of PEMFCs at relatively high humidity improves the ammonia tolerance. Zhang et al [11] proposed NH 3 or NH 4 þ could reduce the active area of the catalyst by adsorbing onto Pt surface in contrast to the evidence in Refs.…”