Intermetallic Platinum-Calcium Alloy Breaks the Activity-Stability Trade-Off in Fuel Cell for Enhanced Performance.

The realization of proton exchange membrane fuel cell (PEMFC) as a replacement for combustion engines and batteries in transportation applications demands a catalyst that is not only active but also highly stable throughout the vehicle's longevity. Alloys of platinum with alkaline earth metals have been identified to be active and highly stable owing to their high vacancy formation energies, but their synthesis in nanoparticle form has proven challenging, which discourages most researchers from exploring this area. In this work, the synthesis, characterization, and PEMFC test of platinum-calcium (PtCa) nanoparticles prepared through the solution phase technique are reported. The PtCa catalyst reported here exhibits an intermetallic ordered atomic arrangement with a core-shell configuration, resulting in a specific rated power of 9 W mg at 0.67 V based on the cathode loading under H-air conditions. The reported catalyst also surpasses the US Department of Energy (DOE) 2025 mass activity target with an 81% retention in practical fuel cells after 30 000 durability cycles. This catalyst holds great potential to substitute the Pt-transition alloy catalysts which have thus far fallen short of meeting commercial standards.