Making the Most of Platinum Catalysts in Fuel CellsS. Himmelstein | December 18, 2018
Rare and costly platinum-group metals are used for the demanding oxygen reduction reaction in hydrogen fuel cells. Efforts to reduce the amount of platinum consumed and thereby lower system cost have created nanoparticles with earth-abundant metals to increase their activity and surface area. Another approach replaces the platinum with metals such as cobalt and organics in the form of quinones.
A new highly active and stable electrocatalyst prepared by researchers from the U.S. Department of Energy’s Argonne National Laboratory (ANL) contains an ultralow-loading platinum content. The synthesis method uses cobalt or bimetallic cobalt and zinc zeolitic imidazolate frameworks as precursors.
A cobalt metal-organic framework compound was thermally activated to create oxygen reduction reaction-active cobalt sites. This material served as a substrate for the growth of cobalt-platinum alloy nanoparticle cores coated with thin platinum layers to form a core-shell structure.
The resulting durable catalyst consumes only about a quarter as much platinum as current technology. Two catalysts tested retained 64% and 15% of initial activity values after 30,000 voltage cycles in a fuel cell.