A new category of electrolysis could significantly lower the expenses associated with producing “green” hydrogen. In the new capillary-fed electrolyzer cell — designed by Hysata (Wollongong, Australia; www.hysata.com) based on research from the University of Wollongong (www.uow.edu.au) — water is supplied to electrodes using capillary transport facilitated by a commercially available wicking membrane.
“Rather than having the electrodes surrounded by liquid as in a standard electrolyzer, this wicking membrane takes liquid from a reservoir below the electrodes and delivers targeted electrolyte between the two electrodes. The porous membrane has a very high open area and a much lower electrical resistance than the separators used in other electrolysis methods. This gives us very high current density and low voltages, resulting in a high electrical efficiency with low costs,” explains Paul Barrett, CEO of Hysata.
This configuration also means that the electrodes are continuously coated with a thin layer of electrolyte through which the generated O2 and H2 gases can efficiently travel without forming gas bubbles, which can hinder access to active sites on the electrodes. Being able to directly produce gases at the electrode interfaces without bubbles or froth in the liquid helps the capillary-fed electrolyzers to avoid resistance and mass-transfer inefficiencies experienced in other electrolyzers, and also decreases the amount of water required. According to Barrett, the new electrolyzers work at 95% overall system efficiency, compared to around 75% for current industry-standard electrolysis units — translating to a H 2 production cost of $1.50/kg or less. “The high-efficiency cells enable balance-of-plant simplification in a number of ways, including eliminating the need for cooling, and we can take the gas off the stack at higher pressure, eliminating the need for compression,” he adds.
Hysata has designed the cell architecture to be mass-produced — the cell itself is injection-moldable from widely available polymeric materials, and all other core components, including the wicking membrane, are made of off-the-shelf materials. Furthermore, unlike typical electrolyzers, the electrodes require no precious metals. The team is working on 5-MW cells modules, with gigawatt-scale manufacturing targeted to begin in 2025. These modules will form the building blocks for larger deployments.