Experimental study on the start-up with dry gases from normal cell temperatures in self-humidified proton exchange membrane fuel cells

In this study, the start-up characteristics of PEMFCs (proton exchange membrane fuel cells) was investigated with dry gases from normal cell temperatures above 0 degrees C. Firstly, the effects of flow arrangements (co-flow and counter-flow) were evaluated at a starting cell temperature of 25 degrees C. Then, the start-up was successful in both arrangements, but it showed better performance with counter-flow. In addition, the hydrogen concentration was measured and it showed that hydrogen crossover contributes to the membrane hydration and the first phase of dry start-up. However, although the cell temperature rose above 45 degrees C after start-up form 25 degrees C with counter-flow arrangement, the restart-up after shut-down failed at a starting cell temperature of 45 degrees C regardless of flow arrangements. Considering the needs of restart-up, the available starting cell temperature should be improved. For this, after first sub-step of start-up process, relatively low flow rates were maintained to retain produced water without purge so that the membrane can be hydrated sufficiently. With this modified process, denominated as WSP (water storage process) in this study, the dry start-up became successful at a starting cell temperature of 45 degrees C and the cell performance was remarkably improved especially with counter-flow arrangement. (C) 2015 Elsevier Ltd. All rights reserved.