Electrolyzer Durability at Low Catalyst Loading and with Dynamic Operation

Membrane electrode assembly durability is explored for polymer electrolyte membrane electrolyzers, focusing on catalyst (iridium, Ir) degradation at low loading and dynamic operation. Low catalyst loading and high cell potential are critical to observing durability losses over reasonably short experiments, regardless of test profile. While small losses are seen during steady operation, cycling greatly accelerates performance decreases. Ir dissolution mechanistically drives performance loss, thinning the anode catalyst layer and resulting in increasing kinetic losses during extended operation. While morphological changes to the catalyst layer are found, increasing polarization resistance suggests that degradation at the catalyst/ionomer/membrane interface may also contribute. Electrolyzer operation with model wind and solar profiles results in less severe performance losses compared to triangle- and square-wave potential cycling due to the lower cycling frequency of the renewable profiles. However, in both cases kinetics dominated the loss, indicating that higher cycling rates accelerate loss and can be used to project the impact of intermittency on device lifetime. These results suggest that performance losses impact electrolyzers' abilities to operate with low catalyst loading and intermittent inputs, and that a combination of component development and system controls are needed to limit potential and performance loss. (C) The Author(s) 2019. Published by ECS.