Improving Activity and Stability of ORR Electrocatalysts with Pt-Rich Hollow Nanostructures
This study describes the advantages of hollow nanostructures composed of a Pt-rich outer-layer surrounding a central void. Pt-rich hollow nanoparticles with different Pt-shell thicknesses were synthesized via a method involving the galvanic replacement of Ni atoms by Pt atoms, and the nanoscale Kirkendall effect . Increasing the Pt:Ni stoichiometry from 1:1 to 1:5 in the initial metal precursor solution resulted into a thinner Pt-rich shell and an increased Pt lattice contraction. The specific activity and the mass activity for the ORR at E = 0.95 V vs. RHE of the most active hollow electrocatalyst were 9-fold and 3.6-fold that of a reference solid carbon-supported Pt nanocrystallites with a comparable crystallite size (Figure 1). Their structural stability was investigated at different temperatures ranging from T= 293 to 353 K by identical-location and conventional transmission electron microscopy.
This work was performed within the framework of the Centre of Excellence of Multifunctional Architectured Materials "CEMAM" n° AN-10-LABX-44-01 funded by the "Investments for the Future" program. The authors acknowledge financial support from University of Grenoble-Alpes through the AGIR program (grant # LL1492017G), and from the French national Research Agency through the HOLLOW project (grant # ANR-14-CE05-0003-01).
 L. Dubau, M. Lopez-Haro, J. Durst, L. Guétaz, P. Bayle-Guillemaud, M. Chatenet, F. Maillard, “Beyond conventional electrocatalysts: Hollow nanoparticles for improved and sustainable oxygen reduction reaction activity”, J. Mater. Chem. A. 2 (2014) 18497-18507.