Effect of gas crossover on the cold start process of proton exchange membrane fuel cells

This study develops a transient three-dimensional model to investigate the effect of reactant gas crossover through the membrane on the cold start process of PEM fuel cells. Key operating and structure parameters such as current density, anode/cathode inlet pressure, and membrane thickness are explored. The results reveal that gas crossover enhances ice formation rate and cell temperature rise due to additional hydrogen-oxygen side reactions, increasing both heat and water generations. The dominance of the ice formation rate over the temperature rise rate by gas crossover adds complexity to successful cold starts. Notably, the influence of gas crossover is more pronounced at a lower current density. As the operating current density increases from 0.04 A cm -2 to 0.12 A cm -2, the contribution of gas crossover to the temperature rise rate and ice formation rate decrease from 31.6 % to 11.3 % and from 54.5 % to 16.8 %, respectively. The increase of anode inlet pressure accelerates ice formation and temperature rise, whereas cathode inlet pressure has minimal effect. A thicker membrane mitigates gas crossover and is beneficial to cold start success, especially under a wet initial condition. This study emphasizes the significant role of gas crossover in the PEM fuel cell cold start process, highlighting the imperative consideration of gas crossover in both cold start models and strategy developments.