Sacrificial Templates for Galvanic Replacement Reactions: Design Criteria for the Synthesis of Pure Pt Nanoshells with a Smooth Surface Morphology

The galvanic replacement of sacrificial templates offers one of the most synthetically viable approaches for generating platinum-based nanostructures with impressive catalytic activity. Here, we present template design criteria for the synthesis of morphologically smooth platinum nanoshells which undergo minimal alloying with the template material. The criteria is founded on comparisons of nanoshells derived from reacting substrate-immobilized templates of silver, lead, copper, nickel, and cobalt with aqueous H₂PtCl₆. It is shown that template-surface modifications are the primary mode by which smooth Pt nanoshells are obtained, with template composition playing a secondary role. The degree of alloying is strongly dependent upon whether the template applies tensile or compressive heteroepitaxial strains to the depositing nanoshell. On the basis of these findings, we propose a mechanistic framework and an overall strategy for the synthesis of advanced templates for substrate-based galvanic replacement reactions