The dream of a clean hydrogen economy is haunted by a surprising bottleneck: iridium, one of the rarest metals on Earth. Only about eight tons of iridium are produced globally each year, yet it is an essential catalyst inside the proton exchange membrane (PEM) electrolyzers that split water into hydrogen and in the fuel cells that convert hydrogen back into electricity. Without a reliable way to recycle this silver-white metal, the entire vision of green hydrogen could stumble before it ever scales. Researchers at the University of Delaware have now unveiled a recycling process that recovers both iridium and platinum from used devices without generating the toxic waste streams that plague existing methods, offering a potential lifeline for the hydrogen supply chain.
PEM electrolyzers and fuel cells are electrochemical workhorses. Inside each device, a thin polymer membrane is coated on one side with iridium nanoparticles to drive the oxygen evolution reaction and on the other with platinum nanoparticles to catalyze hydrogen reactions. When electric current flows, water molecules are stripped apart, and when the process reverses, hydrogen stored in tanks rejoins oxygen from the air to release energy. The membrane itself is a high-performance fluorinated polymer, part of the PFAS family of “forever chemicals” that can persist in the environment for decades. Taken together, the membrane accounts for up to 30 percent of the cost of the entire stack, and the precious metal catalysts are even more valuable. As global deployment of electrolyzers accelerates, the circular management of these materials becomes not just an environmental nicety but an economic imperative.
Current recycling strategies come with serious environmental trade-offs. The most common chemical route involves bathing spent catalyst-coated membranes in hot mixtures of sulfuric and nitric acid to dissolve the metals, which leaves behind a hazardous liquid waste that is difficult to treat. Alternatively, pyro-metallurgical processes burn the membrane outright, reducing it to an ash that contains platinum and iridium but releasing fluorine-containing off-gases in the process. Both approaches destroy the membrane and create secondary pollution, undermining the clean credentials of the hydrogen technology they are meant to support.
Safina-E-Tara Siddiqui, a doctoral candidate in mechanical engineering working with Professor Ajay Prasad, took a different approach inspired by everyday home maintenance. “It’s like pressure washing the siding of your house,” Prasad said. “You just sweep across the surface and remove the catalyst material.” Instead of corrosive acids or incineration, the team uses a precisely controlled spray-jet of a benign mixture of isopropyl alcohol and water. The jet is trained onto the surface of the coated membrane, and under the right conditions it lifts the catalyst layers away while leaving the underlying polymer sheet intact and reusable. The process uses no harsh chemicals and no burning, making it a genuinely green recycling method.
One of the cleverest aspects of the technique is its selectivity. The iridium catalyst sits on one face of the membrane and the platinum catalyst on the other. Siddiqui’s jet removes each layer sequentially, keeping the two metals from mixing. If platinum and iridium were commingled during stripping, separating them would require additional energy-intensive purification steps. By recovering them as distinct streams, the method preserves their high value and simplifies their re-introduction into the catalyst supply chain. The membrane, meanwhile, is not sacrificed; it remains in a condition that could allow it to be put back into service after cleaning and inspection, avoiding the release of PFAS and dramatically reducing the cost burden of manufacturing new stacks.
Achieving this precision required intense process engineering. Siddiqui began with beaker-scale immersion experiments, timing how quickly catalyst layers detached from small membrane coupons when heated in different solvent ratios. She then moved to a bench-scale spray rig, running hundreds of tests on pieces the size of a postage stamp while varying temperature, solvent composition, jet velocity, and nozzle distance. A major hurdle emerged when the membrane absorbed enough solvent to swell to nearly twice its original dimensions. The swelling caused the thin film to sag and tear under the force of the jet. To overcome this, she developed a heated vacuum bed that holds the membrane perfectly flat during the delamination process, ensuring a clean, uniform peel of the catalytic coatings.
“Iridium is the major bottleneck in PEM electrolyzers because of this,” Siddiqui explained, referring to the metal’s extreme scarcity – it is never mined as a primary product, only recovered as a byproduct of platinum mining. “That is why we are focusing on recycling them from spent electrolyzers instead of depending on mining or market supply.” The worldwide electrolyzer build-out expected in the next decade could outstrip the available annual iridium production many times over if no recycling loop exists. By turning end-of-life stacks into rich urban mines, the Delaware system tackles this critical materials constraint head-on.
The next phase of the work, published in the International Journal of Hydrogen Energy, will quantify recovery yields down to the sub-milligram scale and characterize the electrochemical activity of the reclaimed catalysts. The team plans to fabricate fresh membrane electrode assemblies using the recovered materials and test their performance in operating cells, closing the loop from scrap back to functional device. The technology has already been advanced toward commercialization through the university’s Office of Economic Innovations and Partnerships, signaling that investors see a near-term pathway to industrial deployment. If successful, the spray-jet recycling concept could help ensure that the hydrogen economy runs not only cleanly but also on a sustainably managed resource loop, where the world’s rarest metals are borrowed rather than buried.
Subject of Research: Green recycling of precious metal catalysts and membranes from PEM electrolyzers and fuel cells using a spray-jet system
Article Title: Green recycling of precious metal catalysts and membranes from PEM electrolyzers and fuel cells using a spray-jet system
News Publication Date: 9-Apr-2026
Web References: https://dx.doi.org/10.1016/j.ijhydene.2026.154430; https://udel.flintbox.com/technologies/2979ce60-31f9-464f-9079-908ecb2dbdb4
References: International Journal of Hydrogen Energy, DOI: 10.1016/j.ijhydene.2026.154430
Image Credits: Not specified
Keywords
Iridium, Platinum, PEM electrolyzer, Fuel cell, Recycling, Green chemistry, Hydrogen economy, Membrane delamination, Spray-jet, University of Delaware, Circular economy
