Résumé
Pt-based electrocatalysts with higher activity and durability are necessary for cost-competitive polymer electrolyte membrane fuel cells. We have combined the high utilization and activity of core@shell nanostructures with the high surface area and stability of atomically thin nanosheets to afford electrocatalysts that show enhanced activity and durability for both cathode and anode reactions. Ru-core@Pt-shell nanosheets with an average thickness of 1.5-4.5 Pt monolayers have an electrochemically active Pt surface area of 112-151 m$^2$ (g-Pt)(-1), 1.4-1.9 times larger than typical Pt/C catalysts. A catalyst with a mono layer Ru-core and an average 3.5 monolayer Pt-shell supported on carbon (Ru@Pt-3.5ML(ns)/C) shows 4.5 times higher mass activity than benchmark Pt/C catalyst for the oxygen reduction reaction with a slower degradation rate, making this nanomaterial one of the most active and durable Pt-based catalysts. For the anode reactions, Ru@Pt-1.5ML(ns)/C shows 2 times higher apparent mass activity for the hydrogen oxidation activity in pure H$_2$ as well as 300 ppm CO containing H$_2$, and better stability against potential cycling.