Synthesis of Pt-Cu Bimetallic Alloys and Their Electrocatalytic Activities for Oxygen Reduction Reaction

One major limitation for the commercialization of proton exchange membrane fuel cells (PEMFCs) is the high cost of oxygen reduction reaction (ORR) catalysts. The predominant catalysts are Pt nanoparticles (NPs) supported on carbon materials. However, there materials present low activity and durability. In this case, unsupported catalysts with high surface area and porosity are promising candidates to improve the activity and durability. The unsupported catalysts would not only eliminate the activity lost caused by erosion of supports but also allow for a thinner electrode catalyst layer and for improved mass transport and Pt utilization. To this end, the three dimensional (3D) nanofoams with PtCu@Pt core-shell structures were synthesized with a facile procedure and etched by nitric acid. After appropriate acid treatment, the catalysts achieve a factor of 3 enhancement in mass activity and a factor of 6 enhancement in specific activity, respectively, compared with commercial Pt/C catalysts. The enhancements are attributed to the high surface area and the special structure. The unsupported PtCu@Pt catalysts are promising materials for ORR.