Performance improvement of self-humidifying PEM fuel cells using water injection at various start-up conditions

A critical issue in self-humidifying proton electrolyte membrane (PEM) fuel cells is to achieve stable performance during start-up. In this study, the start-up characteristics of self-humidifying PEM fuel cells are investigated at various temperatures and voltages. Aquivion and Nafion are used as electrolytes for the performance comparison. Moreover, to overcome start-up failure, the direct water injection strategy is proposed and tested in the self-humidifying PEM fuel cell according to the injection side and amount of injected water. Generally, Aquivion membranes exhibit better start-up performance than Nafion membranes in the self-humidifying PEM fuel cell owing to its higher water absorption capability. The water injection into the anode side is more effective than that into the cathode side in achieving high stability and steady-state current density in the self-humidifying PEM fuel cells. With the water injection during start-up, the steady-state current density of the self-humidifying PEM fuel cell with Aquivion is 32% on average higher than that with Nafion. In addition, the optimal amount of water injection is dependent on the water absorption capability of the membrane at the start-up conditions.