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

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.