Experimental Characterization of the Poisoning Effects of Methanol-Based Reformate Impurities on a PBI-Based High Temperature PEM Fuel Cell

Abstract

Abstract:In this work the effects of reformate gas impurities on a H 3 PO 4 -doped polybenzimidazole (PBI) membrane-based high temperature proton exchange membrane fuel cell (HT-PEMFC) are studied. A unit cell assembly with a BASF Celtec ® -P2100 high temperature membrane electrode assembly (MEA) of 45 cm 2 active surface area is investigated by means of impedance spectroscopy. The concentrations in the anode feed gas of all impurities, unconverted methanol-water vapor mixture, CO and CO 2 were varied along with current density according to a multilevel factorial design of experiments. Results show that all the impurities degrade the performance, with CO being the most degrading agent and CO 2 the least. The factorial analysis shows that there is interdependence among the effects of the different factors considered. This interdependence suggests, for example, that tolerances to concentrations of CO above 2% may be compromised by the presence in the anode feed of CO 2 . Methanol has a poisoning effect on the fuel cell at all the tested feed ratios, and the performance drop is found to be proportional to the amount of methanol in feed gas. The effects are more pronounced when other impurities are also present in the feed gas, especially at higher methanol concentrations.

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

“…However, prolonged exposure to CO may cause irreversible degradation [11]. The poisoning effect of CO in HT-PEMFCs is reduced due to their higher operating temperature, where lower surface adsorption of CO on the Pt-surface combined with increased electro-oxidation of CO to CO 2 leads to a significant improvement in tolerance compared to LT-PEMFCs [3,11,15]. compare EIS measurements of different single cell sizes.…”

Role of the microporous layer in the redistribution of phosphoric acid in high temperature PEM fuel cell gas diffusion electrodes

“…The elevated operating temperature of the HT-PEMFC simplifies the system layout requirements significantly and eliminates the liquid water management challenges that LT-PEMFCs typically face. Compared to LT-PEMFCs, stack cooling and heat recovery become more effective [9,10], and tolerances to fuel impurities increase (up to 3-5% CO), which provide the added benefit of fuel flexibility [11][12][13]. Reactant humidification is not required, which further simplifies water management within the system [1].…”

Methyl phosphate formation as a major degradation mode of direct methanol fuel cells with phosphoric acid based electrolytes

“…They reported a degradation rate of 2e5 mV h À1 , attributed to the migration of acid towards the anode and suggested to improve the barrier effect of the micro porous layer of the electrodes. Araya et al [18,19] investigated the performance of a phosphoric acid doped polybenzimidazole membrane based fuel cell, and observed a dramatic increase of the area specific resistance when the methanol concentration in the anode feed was increased up to 8 vol.%.…”