Numerical study of anode side CO contamination effects on PEM fuel cell performance; and mitigation methods

Abstract

In the present work, a two-dimensional, transient, isothermal, two-phase, multicomponent transport model was considered for the anode-side electrode of a PEMFC. The governing equations of two-phase flow in the PEM fuel cell were discretized by finite volume method, and the SIMPLE algorithm was used to handle the pressure-velocity coupling. The discretized governing equations of the model were numerically solved on a non-uniform grid with an in-house developed code. The simulation was performed for velocity, pressure, concentration of species, and liquid water saturation in the anode side of the PEMFC. At first, the steady-state and transient effects of introducing the CO-contaminated hydrogen on the cell performance were investigated. Then, a comprehensive investigation of the commonly used mitigation techniques including the effect of air or oxygen bleeding, elevation of temperature and the effect of using CO-tolerant catalysts (PtRu/C), was conducted. The numerical results of the model were compared and validated with the experimental data. The results indicated that even using a low CO concentration, leads to significant degradation of the fuel cell output current density (about 30% of the output current was lost within 30 min when the hydrogen is pre-mixed with 15 ppm of CO as the fuel). Injecting a small amount of air into the anode stream, resulted in fast recovery of the lost current density (by injecting about 5% air into the fuel, 80% of the output current was recovered within 2 min at 53 ppm CO). Higher air bleeding ratio only resulted in minor improvement of the cell performance. Increasing the cell temperature; also using PtRu/C instead of Pt/C (at low temperatures) led to improving the cell performance. The use of PtRu/C at a high operating temperatures only resulted in minor improvement of the cell performance.