Study of water accumulation dynamics in the channels of an open-cathode fuel cell through electro-thermal characterisation and droplet visualisation

The results reinforce the importance of cell temperature for water management, which is a function of current density. Regions of the cell with higher temperature avoid flooding by promoting vapour phase water; however, this can lead to higher membrane resistance due to dehydration. The results reveal that transition in the water balance regime from continuous hydration and flooding to drying with increasing current density occurs between 34 °C-40 °C (at 250 mA cm−2) and water generation is balanced with evaporation at ∼50 °C (550 mA cm−2). Finally, fuel cell orientation affects performance after extended operation due to the effect of water accumulation and evaporation, with the cathode in a 'flat upwards' orientation found to be most resistant to flooding and cathode in a flat downwards orientation the most likely to flood.