Durable Catalysts and Membranes for AEM Electrolyzer Operated with Impure Water

Renewable energy has the potential to supply energy worldwide, but because of its variable power output it needs to be coupled with energy storage. Electrochemical electrolysis can split water into hydrogen and oxygen, which can be stored and re-converted into electricity later. However, this process requires ultrapure water, which is unavailable in many areas in the world, especially in island and coastal regions. Even when the electrolyzer feed water is purified, a failure or poor performance in the water clean-up system could expose the electrolyzer to impure water, reducing its performance (often permanently) or deactivating it altogether. Thus, there is a real need for electrolyzers that can tolerate impure water. This project will develop stable catalysts and membranes for use in anion exchange membrane (AEM) electrolyzer stacks; these improved catalysts and membranes will tolerate exposure to low quality water. The membrane has an active skin that selectively rejects contaminants (such as organic compounds and ions) from impure water and only allows the conduction of hydroxide (OH-) ions. This nanoporous polymer skin will consist of both chemically stable and ionically conductive domains that self-assemble into complex nanostructures with interconnected ionic channels, allowing only hydroxide ions to travel across the membrane. Thus, TDA’s AEM electrolyzer will be corrosion free and selectively, reliably and affordably produce hydrogen and oxygen from impure water. The key to making AEM electrolyzer work with impure water lies in the use of the right catalysts and supports. In Phase I, TDA will first develop conductive materials to support and stabilize the catalyst metals. Next, we will coat our active polymer on commercial AEM membranes, producing a highly selective layer to reject salt ions or other contaminants. We will measure the catalyst activity as well as the membrane’s ion exchange capacity, hydroxide conductivity, and salt rejection capability. Lastly, we will test these catalysts/membranes in an electrolyzer under a range of salt concentrations and measure their performance and stability. Commercial applications include long-duration electrolysis of impure water, especially in island and coastal regions, to manufacture hydrogen for use in fuel cells, synthesis gas-to-transportation fuels, and back-up power systems.