Synthesis of Bimetallic Au@Pt Nanoparticles with Au Core and Nanostructured Pt Shell toward Highly Active Electrocatalysts

摘要

Au@Pt nanocolloids with nanostructured dendritic Pt shells are successfully synthesized by chemically reducing both H2PtCl6 and HAuCl4 species in the presence of a low-concentration surfactant solution. By applying an ultrasonic treatment, the particle size of the Au@Pt nanocolloids is dramatically decreased and their size distribution becomes very narrow. The difference in reduction potentials of the two soluble metal salts (Au(III) and Pt(IV) species) plays a key role in the one-step synthesis of the core-shell structure. Because of the different reduction potentials, the reduction of Au ions preferentially occurs over a short time to form the Au seeds. It is followed by overgrowth of Pt nanodendritic nanowires on the Au seeds, which is confirmed by ultraviolet—visible light absorption spectroscopy and transmission electron microscopy. Interestingly, the Pt shell thicknesses on Au cores can be easily tuned by controlling the Pt/Au molar ratios in the starting precursor solutions. Through the optimization of the Pt shell thicknesses, the Au@Pt nanocolloids can exhibit enhanced activity as an electrocatalyst for a methanol oxidation reaction, which will be important to improve the utilization efficiency of Pt catalysts in the future.