Cage-bell structured Au–Pt nanomaterials with enhanced electrocatalytic activity toward oxygen reduction

Mastery over the structure of nanomaterials enables control of their properties and enhancement of their usefulness for a given application. Herein we report a template-based approach for the synthesis of Au–Pt nanomaterials with cage-bell structures. Typically, Au nanoparticles with narrow size distributions are prepared first, followed by the Ag coating. Then PtII ions are reduced using citrate in the presence of core–shell Au–Ag nanoparticles, resulting in the formation of core-shell-shell Au–Ag–Pt nanoparticles with discontinuous Pt shells. Finally, Ag is removed using bis(p-sulfonatophenyl)phenylphosphane, leaving behind the hydrosol containing the Au–Pt nanomaterials with cage-bell structures. The cage-bell structured Au–Pt nanomaterials have displayed superior catalytic activity toward oxygen reduction in proton-exchange membrane fuel cells because of their relatively higher surface areas than their solid counterparts (the nano-channels on the Pt shell permit the access of the inner surface areas), and the electronic coupling effect between the inner-placed Au core and the Pt shell.