Tailoring the Structure and Property of Pt-Decorated Nanoporous Gold by Thermal Annealing

We study the structure evolution of a novel electrocatalyst, Pt-decorated nanoporous gold (Pt-NPG), during thermal annealing at relatively low temperatures. Pt-NPG was made by plating a thin layer of Pt over NPG Substrate during an electroless plating process that generated epitaxial Pt nanoislands loaded on the NPG surface. In comparison with Pt's very high melting point, thermal annealing at temperatures as low as 100 degrees C was found to significantly change the structure and surface chemistry of these nanomaterials. Scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques were combined to characterize the structures of Pt-NPG annealed under various conditions. While Pt-NPG preserved very well its initial porous morphology, the deposited Pt islands collapsed to form a thin Au-Pt alloy layer coating on the NPG surface upon heating. This structure change results in severe modulation to the electronic structure and surface reactivity of Pt, which were proved by markedly different behaviors in electrocatalytic reactions such as formic acid electro-oxidation and CO stripping. These findings provide considerable insight into the Au-Pt bimetallic system and pave the way for the application of Pt-NPG in fuel cell technologies.