科研之友
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摘要
Platinum surface-enriched bimetallic PtPd nanoparticles are synthesized via a facile and eco-friendly approach. Significantly different formation processes of single Pt, Pd, and bimetallic PtPd nanoparticles under various conditions have been monitored by UV-visible spectra. The size of the bimetallic Pt-Pd nanoparticles has been found to be significantly affected by the pH of the starting precursor solutions. Uniform bimetallic Pt-Pd nanoparticles with an average diameter of similar to 3 nm are formed in the basic solutions; however, the particle size can be as large as 11 nm when synthesized in acidic media. The detailed morphology, composition, and structure of the carbon-supported bimetallic Pt-Pd electrocatalysts have been extensively characterized and correlated with their electrochemical properties as evaluated using cyclic voltammetry and single-cell test. The formation of Pt surface-enriched Pt-Pd bimetallic nanoparticles has been confirmed by X-ray photoelectron spectroscopy and has been interpreted by the exclusively reduced Pt around the newly formed Pd nuclei due to the catalytic action of Pd, which in turn curbs the unfavorable growth of the bimetallic nanoparticles. The electrochemical tests indicate that the optimized Pt-Pd/C with reduced cost exhibits competitive catalytic performance toward oxygen reduction reaction and superior tolerance to methanol over the state-of-the-art Pt/C.
