Remarkable Improvement of the Catalytic Performance of PtFe Nanoparticles by Structural Ordering and Doping.

To achieve fuel cell commercialization, the performance improvement and cost reduction of catalysts are still the main challenges. To enhance the catalytic activity and durability for oxygen reduction reaction (ORR), we prepare Au-PtFe particles entrapped in a porous carbon and then convert them to have a fine-grained and highly ordered intermetallic structure. The optimal Au-PtFe particles in catalyzing ORR exhibit initial specific and mass activities 9 times higher than the commercial catalyst of Pt/C. Such a large enhancement is much higher than most of the Pt-based ordered intermetallic catalysts reported in the literature. Accelerated durability testing induces little degradation of the catalytic activity to the ordered structure, particularly the Au-doped one, after potential cycling for many thousands of cycles under harsh electrochemical conditions involving an acidic medium and a high potential range of 0.66-1.3 V. This is in big contrast with the large degradation shown by most previous catalysts. The excellent activity and durability are attributed to synergistic effects of the fine-grained and ordered structure of the particles, the confining support of the porous carbon, and the homogeneous incorporation of a trace amount of Au. The new intermetallic catalyst of Au-PtFe/C represents a new strategy for performance enhancement and cost reduction and thus promotes practical applications of proton-exchange membrane fuel cells.