(166f) Novel Seawater Electrolyzer Design with High-Rate Passive Water Transport

As the world pushes decarbonization efforts toward achieving Net Zero carbon emissions, green hydrogen has received an enormous amount of attention as a promising energy carrier. However, for each kilogram of hydrogen to be produced, 9 kg of water needs to be consumed. Traditionally, fresh water is used as the inlet source for electrolysis, but the very large volume of clean water that will be required for H₂ production in the coming decades has the potential to worsen the shortage of fresh water in many parts of the world.

To avoid the competition between energy, agriculture and residential water uses, the use of seawater as a water source has been extensively discussed in recent years. Unfortunately, direct seawater electrolysis is plagued by several challenges including the formation of competitive chloride by-products at the anode, electrode corrosion, and precipitation of divalent cations at the cathode limiting its performance and lifespan. To avoid this, traditional systems first desalinate the seawater by reverse osmosis (RO) before being utilized for green hydrogen production. But the energy intensity of RO coupled with membrane fouling and increased system complexity makes it preferable to operate without the RO step. Therefore, modern solutions often focus on designing corrosion-resistance electrodes, these technologies are still far away from practical implementation, and limiting the operating voltage (which increases capital cost and system size).

Therefore, this work focused on overcoming the issues associated with direct seawater electrolysis using a novel design that is called the osmosis-driven electrolyzer cell (ODEC). This reactor places concentrated electrolyte solutions and simulated seawater on either side of membranes that allow for water transport into the electrolyte solutions without significant ion transport. The electrolyte solution accepts the water from the seawater and that solution is used to drive electrolysis and H₂ generation. This talk will give an insight into multiple cell designs around the ODEC concept, with a discussion of strengths and weaknesses. We systematically manipulated membrane properties, cell geometry and cell operating conditions to improve device efficiency and performance. The experimental results are supported by computational fluid dynamics modeling, providing further insight into the cell behavior. Lastly, data will be shown where electrolyzers are durably run for 100’s of hours.