Etching approach to hybrid structures of PtPd nanocages and graphene for efficient oxygen reduction reaction catalysts

Cathodic oxygen reduction reaction (ORR) is a highly important electrochemical reaction in renewable-energy technologies. In general, the surface area, exposed facets and electrical conductivity of catalysts all play important roles in determining their electrocatalytic activities, while their performance durability can be improved by integration with supporting materials. In this work, we have developed a method to synthesize hybrid structures between PtPd bimetallic nanocages and graphene by employing selective epitaxial growth of single-crystal Pt shells on Pd nanocubes supported on reduced graphene oxide (rGO), followed by Pd etching. The hollow nature, {100} surface facets and bimetallic composition of PtPd nanocages, together with the good conductivity and stability of graphene, enable high electrocatalytic performance in ORR. The obtained PtPd nanocage-rGO structures exhibit mass activity (0.534 A·mg_Pt^-1) and specific activity (0.482 mA·cm^-2) which are 4.4 times and 3.9 times greater than the corresponding values for Pt/C.