Crystal-Phase-Change-Induced Formation of Defect-Rich Pt–Ag Nanoshells for Efficient Electrooxidation of Formic Acid

Abstract

In recent years, defect engineering has proven to be a powerful approach for enhancing the electrocatalytic performance of nanomaterials. To advance the application of defect-rich nanomaterials, it is critical to develop new defect engineering strategies. In this study, we propose a new strategy for creating an abundance of defects in ultrathin metal nanomaterials by crystal phase engineering. Specifically, we synthesized hexagonal close-packed (hcp)/face-centered cubic (fcc) Ag@Pt core/shell nanoechinus by using hcp/fcc mixed-phase Ag nanoechinus as templates through epitaxial growth. Selective etching of the Ag templates resulted in a transformation of the epitaxial layer from the hcp to the fcc crystal phase, along with the formation of abundant defects in the Pt–Ag nanoshells (Pt–Ag NSs). Subsequently, we employed thermal annealing to produce porous walls in the defect-rich Pt–Ag NSs. Compared to commercial Pt/C, the resulting defect-rich Pt–Ag NSs with ultrathin and porous walls demonstrated superior electrocatalytic performance in formic acid oxidation due to their unique porous, ultrathin, defect-rich, and alloy structures. Our findings highlight a new application of crystal phase engineering for synthesizing defect-rich nanomaterials and may lead to new opportunities for engineering the electrocatalytic properties of metal nanomaterials through defect engineering.