Effects of Impurities on Pre-Doped and Post-Doped Membranes for High Temperature PEM Fuel Cell Stacks

Abstract

In this paper, we experimentally investigated two high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) stacks for their response to the presence of reformate impurities in an anode gas stream. The investigation was aimed at characterizing the effects of reformate impurities at the stack level, including in humidified conditions and identifying fault features for diagnosis purposes. Two HT-PEMFC stacks of 37 cells each with active areas of 165 cm2 were used with one stack containing a pre-doped membrane with a woven gas diffusion layer (GDL) and the other containing a post-doped membrane with non-woven GDL. Polarization curves and galvanostatic electrochemical impedance spectroscopy (EIS) were used for characterization. We found that both N2 dilution and impurities in the anode feed affected mainly the charge transfer losses, especially on the anode side. We also found that humidification alleviated the poisoning effects of the impurities in the stack with pre-doped membrane electrode assemblies (MEA) and woven GDL but had detrimental effects on the stack with post-doped MEAs and non-woven GDL. We demonstrated that pure and dry hydrogen operation at the end of the tests resulted in significant recovery of the performance losses due to impurities for both stacks even after the humidified reformate operation. This implies that there was only limited acid loss during the test period of around 150 h for each stack.

Challenges and opportunities for characterisation of high-temperature polymer electrolyte membrane fuel cells: a review

“…This capability has been used to determine the effects of operating conditions, degradation, and design optimisation. 145,179,[271][272][273][274] EIS data can be analysed using equivalent circuit models (ECMs). These models can consist of a combination of resistors, capacitors, inductors, and specialised electrochemical components (Warburg diffusion and constant phase elements).…”

“…269,280 This has been reported in both HT-PEMFCs and LT-PEMFCs. 272,279,281 The Z re (also denoted: Z 0 ) axis intercept at high frequencies, oen referred to as HFR, is ascribed to ohmic resistance. 262 As proton conductivity dominates ohmic resistance, the intercept is used to indicate electrolyte characteristics.…”

“…The impact of CO and other species such as CO 2 have also been studied using DRT. 272,301 Generally, the introduction of CO and other species does not improve performance, but synergistic effects may occur when species such as H 2 O, CO 2 , and CH 3 OH are also present. However, improvements appeared to depend on current density and can be minimal.…”

Technologische Pfade für die Herstellung von komprimiertem und hochreinem Wasserstoff mit Hilfe von Sonnenenergie

“…Derzeit werden PEM [305, 308, 310, 316–321] für Niedertemperatur‐EHC bevorzugt, da sie eine hohe Selektivität und eine H 2 ‐Reinheit von >99.9 % ermöglichen [305, 322] . Sie sind jedoch anfällig für Vergiftungen durch CO, NG‐Geruchsstoffe, CO 2 , S‐Spezies usw.…”

Technological Pathways to Produce Compressed and Highly Pure Hydrogen from Solar Power

“…Presently, PEM [305, 308, 310, 316–321] are preferred for low‐temperature‐EHC, enabling high selectivity and H 2 purity of >99.9 % [305, 322] . However, as a limitation, they are susceptible to poisoning by CO, NG odorants, CO 2 , S species, etc.…”