| Target-oriented design and controlled synthesis of noble-metal nanoparticles(NPs)have aroused extensive attention because of their important applications in diverse fields,such as nanocatalysis,chemical sensing,and drug delivery.In particular,in clean energy technology like fuel cells,Pt-based NPs are still the most efficient material for the key electrocatalytic reactions.To minimize the consumption of expensive Pt and optimize the catalytic performance,tremendous efforts have been devoted to synthesizing multi-metallic NPs,due to their superiorities in selectivity,activity and/or stability in comparison to corresponding monometallic counterparts.A straightforward physical approach is developed to synthesize carbon nanotubes supported nanoparticles,and it allows predesign and control of the metal variety and composition by simply adjusting the sputtering targets and conditions.In our work,we synthesized the supported monometallic(Au,Pd,Pt)nanoparticles,bimetallic(Au@Pt,Pd@Pt,Au@Pd)nanoparticles and different atomic ratio of trimetallic PdAu@Pt(3:1:2,2:2:2,1:3:2)nanoparticles.The small-sized PdAu@Pt nanoparticles act as the high-performance nanocatalysts for methanol oxidation reaction,showing higher electrocatalytic activity and stability compared with the corresponding Pt-based bimetallic NPs and commercial Pt/C catalyst.The features of alloying and charge redistribution are demonstrated in the PdAu@Pt nanoparticles,which highly depend on the Pd:Au:Pt ratio.With an appropriate compositional ratio,the significant electron gaining of Pt upon alloying may be responsible for the promoted electrocatalytic performance of the trimetallic nanostructures.The main works can be summarized as follows:(1)Using ionic liquid sputtering method,we synthesized carbon nanotube-supported Au,Pd and Pt monometallic nanoparticles conveniently,Au@Pt and Pd@Pt bimetallic nanoparticles via two-step sputtering deposition,and Au@Pd bimetallic nanoparticles with one-pot sputtering deposition.Based on above specific approaches,a straightforward physical approach is developed to synthesize the multi-walled carbon nanotubes supported PdAu@Pt trimetallic nanoparticles,which is the environmental-friendly and byproduct-free,and it allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions.(2)The systematic characterizations were carried out to acquire the compositional ratios,microscopic structures,crystalline structures,electronic structures of the supported NPs successively by inductively coupled plasma atom emission spectroscopy(ICP-AES),transmission electron microscopy(TEM)and high-angle annular dark-field scanning TEM(HAADF-STEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and X-ray absorption near-edge spectroscopy(XANES).Based on these characterization results,it has a significant importance to analysis its synergistic effects with catalytic performance of methanol oxidation reaction(MOR).(3)According to studying the catalytic performance of Pd@Pt and Au@Pt bimetallic NPs and PdAu@Pt trimetallic NPs with high compositional controllability decorated on carbon nanotubes(CNTs),we conclude that the supported PdAu@Pt trimetallic NPs exhibit the prominent superiority in catalytic performance for MOR compared with both the corresponding bimetallic NPs and commercial Pt/C catalyst.The compositional control in the PdAu@Pt NPs by setting sputtering conditions enables the tuning of their catalytic behaviors,and the optimal catalytic activity and stability are achieved at the Pd:Au:Pt atomic ratio of 3:1:2.The structural and electronic characterizations reveal the alloying of the metal components,and the evident charge redistribution in the PdAu@Pt NPs depending on the compositional ratio is considered to be responsible for the synergistic effects observed in the MOR measurements. |
PDF Full Text Request