Deterioration Behavior of Pt in a Pt/Au Nanoparticle-Loaded Carbon Black Catalyst Analyzed by an Accelerated Durability Test

Au nanoparticles with 2.5 +/- 0.5 nm in size were prepared on carbon black by bubbling CO as a reducing agent in a KAuCl4 aqueous solution containing glutathione as a stabilizer (Au-G/CB). The Au-G/CB after heat treatment (Au-G/CB-HT) had the particle size of 2.8 +/- 0.5 nm. Pt monolayer was deposited on the Au nanoparticles by underpotential deposition and the following galvanic replacement (Pt/Au-G/CB-HT). The activity per unit mass of Pt for oxygen reduction reaction at 0.9 V for the Pt/Au-G/CBHT was ca. 6 tis as high as that of commercial Pt/CB. In durability tests, the former was more stable than the latter. The decrease in electrochemical surface area of Pt for the Pt/Au-G/CB-HT for the initial 2000 cycles was caused by both anodic dissolution of Pt into the electrolyte solution and formation of solid solutions of Pt and Au, while after 2000 cycles it was significantly suppressed.