In the present study we compare different nanoparticle (NP) composites (nanocomposites) as potential electrocatalysts for the oxygen reduction reaction (ORR). The nanocomposites consist of a mixture of Pt and Ir NPs and Pt and Au NPs, respectively, that are immobilized onto a high surface area carbon support. Pt NPs supported on the same carbon support serve as benchmark. The performance testing was performed in a conventional rotating disk electrode (RDE) setup as well as in a recently introduced gas diffusion electrode (GDE) setup providing high mass transport conditions. The ORR activity is determined, and the degradation tested using accelerated degradation tests (ADTs). It is shown that with respect to the benchmark, the Pt – Au nanocomposite concept exhibits improved ORR activity as well as improved stability both in the RDE and the GDE measurements. By comparison, the Pt – Ir nanocomposite exhibits improved stability but lower ORR activity. Combining the GDE approach with small angle X-ray scattering, it is shown that the improved stability of the Pt – Au nanocomposite can be assigned to a reduced Pt particle growth due to the adjacent Au NPs. The results demonstrate that nanocomposites could be an alternative catalyst design strategy complementing the state-of-the-art alloying concepts.
Du et al. SI revised