Intermetallic FePt@PtBi Core-Shell Nanoparticles for Oxygen Reduction Electrocatalysis.

The development of active and stable platinum (Pt)-based oxygen reduction reaction (ORR) electrocatalysts with good resistance to poisoning is a prerequisite for widespread practical application of fuel cells. One effective strategy for enhancing the electrocatalytic performance is to tune or control the physicochemical state of the Pt surface. Here, we demonstrate a general surface-engineering approach to prepare a range of nanostructured Pt alloys by coating chemically ordered intermetallic phases with alloy PtBi shells. FePt@PtBi core-shell nanoparticles showed the best ORR performance with a mass activity of 0.96 A mg Pt -1 and a specific activity of 2.06 mA cm -2 , respectively 7 times and 11 times those of the corresponding values for benchmark Pt/C. Moreover, FePt@PtBi shows much better tolerance to methanol and carbon monoxide than conventional Pt-based electrocatalysts. The observed comprehensive enhancement in ORR performance of FePt@PtBi can be attributed to the increased compressive strain of the Pt surface due to in-plane shearing resulting from the presence of the large Bi atoms in the surface-structured PtBi overlayers, as well as charge displacement via Pt-Bi bonding which mitigates crossover issues.