Electrocatalysis of oxygen reduction on carbon-supported Pt–Co nanoparticles with low Pt content

The oxygen reduction reaction (ORR) was investigated on carbon-supported Pt–Co nanoparticle electrocatalysts with low Pt content in alkaline electrolyte. High resolution transmission electron microscopy, In situ X-ray absorption spectroscopy, and X-ray diffraction analysis evidenced large structural differences of the Pt–Co particles depending on the route of the catalyst synthesis. It was demonstrated that although the Pt–Co materials contain low amounts of Pt, they show very good activities when the particles are formed by a Pt-rich shell and a Pt–Co core, which was obtained after submitting the electrocatalyst to a potential cycling in acid electrolyte. The high activity of this material was due to a major contribution from its higher surface area, as a result of the leaching of the Co atoms from the particle surface. Furthermore, its high activity was ascribed to a minor contribution from the electronic interaction of the Pt atoms, at the particle surface, and the Co atoms located in the beneath layer, lowering the Pt d-band center. As these electrocatalysts presented high activity for the ORR with low Pt content, the cost of the fuel cell cathodes could be lowered considerably.