The future hydrogen economy may hinge on iridium, a metal so rare that only about eight tons are produced worldwide each year. To help stretch the limited supply, University of Delaware researchers have developed a recycling process that recovers precious metals and other materials from used hydrogen-energy devices without producing toxic waste.
Among the technologies driving hydrogen energy are proton exchange membrane (PEM) electrolyzers and fuel cells, which rely on catalysts made from iridium and platinum to produce and use hydrogen efficiently. PEM electrolyzers use electricity to split water into hydrogen and oxygen, while PEM fuel cells release stored energy by converting hydrogen back into electricity.
Platinum and especially iridium are difficult to obtain, expensive and in high demand. To recover these catalysts from used membranes, Safina-E-Tahura Siddiqui, a doctoral candidate in mechanical engineering working under the supervision of Ajay Prasad , developed a spray-jet method that enables recycling of both the precious-metal catalysts and the membrane itself.
“It’s like pressure washing the siding of your house. You just sweep across the surface and remove the catalyst material,” explained Prasad, Engineering Alumni Distinguished Professor of Mechanical Engineering and associate director of the Center for Clean Hydrogen .
Their approach, reported in the International Journal of Hydrogen Energy , is now being advanced toward commercialization through UD’s Office of Economic Innovations and Partnerships.
Recycling becomes more important as demand for PEM technologies grows. Platinum is typically found in very low concentrations in mined ore, while iridium is not mined as a primary material and is recovered only as a byproduct of platinum mining.
“Iridium is the major bottleneck in PEM electrolyzers because of this,” Siddiqui said. “That is why we are focusing on recycling them from spent electrolyzers instead of depending on mining or market supply.”
While recycling catalysts from used PEM electrolyzers and fuel cells is not a new idea, existing methods come with environmental drawbacks. Some rely on harsh chemicals such as sulfuric and nitric acid, which generate toxic waste streams. Others involve burning the membrane to produce ash containing platinum and iridium, a process that can release fluorine-containing emissions.
In contrast, Siddiqui’s approach uses a controlled spray of isopropyl alcohol and water to detach the precious metals from the membrane.
“It is a green recycling method that uses no harsh chemicals and no burning,” said Prasad.
Unlike other recycling approaches that focus solely on recovering metals, the UD method preserves the membrane itself, while also extracting platinum and iridium separately.
The industry-standard membranes used in PEM electrolyzers and fuel cells account for 20 to 30% of the cost of the stack, the central assembly where the electrochemical reactions occur. These membranes are made of polymers classified as PFAS, “forever chemicals” that persist in the environment for decades and contribute to contamination concerns.
The catalyst-coated membrane contains platinum and iridium catalyst layers on opposite sides. The UD researchers’ approach removes each layer sequentially, preserving the membrane while keeping the recovered platinum and iridium separate. If the metals mix during recycling, separating them becomes much more difficult.
Though the principle behind the new recycling method is straightforward, the process requires careful control of jet velocity, solvent ratio, distance and temperature.
Siddiqui began with small-scale beaker tests, immersing tiny pieces of catalyst-coated membrane in solvent, heating them and timing how quickly the catalyst detached. She then conducted hundreds of experiments with membranes roughly the size of a postage stamp, varying temperature, solvent ratio and exposure time to determine optimal conditions.
One challenge emerged when the membrane interacted with the solvent. In some cases, it swelled to nearly twice its original size, causing it to sag and tear during jetting.
To overcome this problem, Siddiqui developed a heated vacuum bed that held the membrane flat while the catalyst layers were removed from each side.
The researchers’ goals extend beyond recovering materials. In the next phase of the work, they will quantify recovery yields, characterize the recovered catalysts and membranes and test their performance in operating electrochemical cells.
Ultimately, they hope recovered catalysts and membranes will be reintroduced into new hydrogen-energy devices, helping create a more sustainable and resilient supply chain for technologies critical to the clean-energy transition.
International Journal of Hydrogen Energy
10.1016/j.ijhydene.2026.154430
Green recycling of precious metal catalysts and membranes from PEM electrolyzers and fuel cells using a spray-jet system
9-Apr-2026