Three-dimensional non-isothermal modeling of carbon monoxide poisoning in high temperature proton exchange membrane fuel cells with phosphoric acid doped polybenzimidazole membranes

Abstract

The performance of proton exchange membrane fuel cell (PEMFC) degrades when carbon monoxide ( CO) is present in the supplied fuel, which is referred to as CO poisoning. Even though the high temperature PEMFC (HT-PEMFC) with a typical operating temperature range from 100 °C to 200 °C features higher CO tolerance than the conventional PEMFC operating at lower than 100 °C, the performance degradation of HT-PEMFC is still significant with high CO concentrations (e.g. ⩾0.5% CO by volume at 130 °C) in the supplied fuel. In this study, a CO poisoning model is developed for HT-PEMFCs with phosphoric acid doped polybenzimidazole (PBI) membranes. The present three-dimensional non-isothermal model compares well with published experimental data at various operating temperatures and CO concentrations in the supplied fuel. It is found that the CO adsorption/desorption processes follow Langmuir kinetics in HT-PEMFCs instead of the well-known Temkin kinetics in conventional PEMFCs. The results indicate that a HT-PEMFC can operate with sufficiently good performance at 130 °C or higher with hydrogen gas produced by methanol reforming with selective oxidation process, and at 160 °C or higher even without the selective oxidation process. At high current densities, it is also observed that severe performance degradation due to CO poisoning only occurs if the volume averaged hydrogen coverage is lower than 0.1 in the anode catalyst layer (CL).