Tailoring the particle sizes of Pt₅Ce alloy nanoparticles for the oxygen reduction reaction

Pt-rare earth (RE) alloys are among the most efficient catalytic materials for the oxygen reduction reaction in acidic media, which, however, are very difficult to synthesize. Previous theoretical and experimental studies indicated that the optimum particle structure is the Pt₅RE intermetallic phases with the optimum sizes of around 6–9 nm. In this work, using a synthesis method recently developed by our group, we attempt to synthesize such alloy catalysts. Firstly, we explored the synthesis conditions to obtain pure-phase Pt₅Ce. Secondly, we attempted to control the size of the alloy particles, which turned out to be the main challenge of this study. To that end, we have investigated the growth pattern of the particles during the synthesis process and used two synthesis parameters, the metal loading and the surface area of the carbon support, to tailor the particle sizes. The sizes and oxygen reduction reaction (ORR) performance of the best Pt₅Ce/C sample obtained so far are discussed.