Strategic synthesis of mesoporous Pt-on-Pd bimetallic spheres templated from a polymeric micelle assembly
Core-shell-corona type triblock copolymer poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) micelles have been selected here to direct the synthesis of mesoporous Pt-on-Pd spheres, consisting of a Pd concentrated core and a Pt shell, as established by elemental mapping. It is important to note that the size of the PS core determines the resultant size of the mesopores. A self-evaporation method has been developed to prepare swollen micelles, so as to further enlarge the pore size (∼40 nm). Compared with commercially available catalysts (e.g., Pt black or Pt, 20 wt% on carbon black), good oxygen reduction reaction performance on the mesoporous Pt-on-Pd spheres is observed, due to the exposure of the most active Pt (111) planes and the synergistic effects from Pt and Pd in the pseudo core-shell structure.