Cleaning up hydrogen energy

Hydrogen could play an important role in meeting the world's sustainable energy needs. It can serve as a fuel source, an energy carrier and an energy storage medium.

However, the future hydrogen economy may hinge on iridium, a metal so rare that only about eight metric tons are produced worldwide each year - about the same weight as a mid-sized school bus. 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, such as electrolyzers and fuel cells, without producing toxic waste.

For example, proton exchange membrane (PEM) electrolyzers and fuel cells 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, allowing the hydrogen to be used as a power resource. 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.

The researchers reported their approach in the International Journal of Hydrogen Energy and have a patent pending through the Office of Economic Innovation and Partnerships, the unit responsible for managing intellectual property at UD.