Hydrogen generation through water electrolysis offers an interesting prospect to store excess electricity on the grid-scale in the context of future electricity supply scenarios with a large share of inherently intermittent renewable energy (wind, solar). This project was focused at understanding the implications and aging phenomena associated with the operation of a water electrolyzer under dynamic conditions, and addresses key materials issues, such as gas permeability and mechanical robustness of the electrolyte membrane.
A detailed analysis of efficiency loss contributions in the water electrolyzer cell necessitates the availability of relevant diagnostic tools. The ‘mass transport losses’ have so far included various contributions that were not further deconvoluted. We have introduced an analytic tool based on AC impedance spectroscopy used in fuel cells and adapted it to the electrolyzer cell to allow the quantification of proton transport losses in the catalyst layer of the oxygen electrode.
The main challenge towards understanding degradation mechanisms in a polymer electrolyte water electrolyzer (PEWE) is correlating degradation pathways with stressors (temperature, water impurities, high potential, etc.) and failure modes (performance and gas purity deterioration). We studied degradation using accelerated start-stop operation of the electrolyzer and saw more pronounced aging compared to state-state operation, which is of relevance for the dynamic operation of an electrolyzer.
Furthermore, the choice of porous transport layer material was shown to be crucial: the use of a soft carbon material on the hydrogen side (as in fuel cells) significantly reduces material creep, which is critical in particular with thin membrane materials. In this context, we evaluated in-house developed membranes and showed that they show very promising performance at much lower gas permeability. This is particularly important for the development of next generation water electrolyzers.
