Abstract
Bimetallic Au@Pt nanoparticles (NPs) with Pt monolayer shell are of much interest for applications in heterogeneous catalysts because of enhanced catalytic activity and very low Pt-utilization. However, precisely controlled synthesis with uniform Pt-monolayers and stability on the AuNPs seeds remain elusive. Herein, we report the controlled deposition of Pt-monolayer onto uniform AuNPs seeds to obtain Au@Pt core–shell NPs and their Pt-coverage dependent electrocatalytic activity for methanol electro-oxidation. The atomic ratio between Au/Pt was effectively tuned by varying the precursor solution ratio in the reaction solution. The morphology and atomic structure of the Au@Pt NPs were analyzed by high-resolution scanning transmission electron microcopy (HR-STEM) and X-ray diffraction (XRD) techniques. The results demonstrated that the Au@Pt core–shell NPs with Pt-shell thickness (atomic ratio 1:2) exhibit higher electrocatalytic activity for methanol electro-oxidation reaction, whereas higher and lower Pt ratios showed less overall catalytic performance. Such higher catalytic performance of Au@Pt NPs (1:2) can be attributed to the weakened CO binding on the Pt/monolayers surface. Our present synthesis strategy and optimization of the catalytic activity of Au@Pt core–shell NPs catalysts provide promising approach to rationally design highly active catalysts with less Pt-usage for high performance electrocatalysts for applications in fuel cells.
Highlights
Direct methanol oxidation has great potential for generation energy systems for applications in power conversion for the future use in the portable electronic devices [1]
The Au@Pt NPs with different ratio were prepared by a two-step synthesis process
For all Au@Pt/C NPs, the Au oxide reduction peak is not present, which is located at higher potential than Pt and it is characteristic in Au-Pt alloy samples [18], the results indicate that the Au core is completely coated by Pt atoms [47]
Summary
Direct methanol oxidation has great potential for generation energy systems for applications in power conversion for the future use in the portable electronic devices [1]. Exploitation of highly efficient electrocatalysts for the sluggish anodic methanol oxidation reaction (MOR) is found to be primary research area for direct methanol fuel cells (DMFC) development. One promising strategy is to design a catalyst comprising of Pt-monolayer onto a less expensive metallic substrates (Pd, Ag, Au, Ir, Co, etc.) as core–shell structure, which enables 100% utilization of enriched Pt atoms onto the surface of the substrate and high cataytic efficiencies through substrate induced surface strain effects [7,10]
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