| Platinum is widely used as catalysts applied in fuel cell,petrochemical and photoelectrocatalysis.Thus,to further improve their activity,stability and utilization efficiency becomes a key issue in related scientific areas due to the high cost and limited reserve.Fundamental studies of single-crystal model catalysts have demonstrated that high-index planes of platinum-group metals with many low coordination steps and kink atoms generally exhibit much higher catalytic activity and stability than those of the low-index planes,such as {111} and {100}.The preparation and study of the properties of high-index surface structure nanomaterials havegreat significance on the development of new catalysts.Due to the long-term research and accumulation of electrochemical synthesize and electrocatalysis of high-index surface structure noble metal in our laboratory,but the size of catalysis is large,and we almost focused on small organic molecule electrooxidation.In this thesis,we try to synthesize tiny Pt high index crystal and expand the application range of high-index crystal plane nanoparticles.We will study the fluorescence of high-index crystal plane nanoparticles and electrocatalysis of single particle.The main results are as follow:1.The graphene supported THH Pt NCs with a size of sub-10 nm were prepared for the first time via the proposed electrochemically seed-mediated method.The surface structure of the nanocrystal is identified by using HRTEM.The electrocatalytic activity of the catalyst is better than the commercial Pt/C catalyst by using inductively coupled plasma mass spectrometry(ICP-MS)and electrochemical testing.To understand the growth processes of the THH Pt NCs,we measured TEM images of samples prepared at the different time of SWP treatment.The result shows that the formation process contains dissolution,growth,and surface reconstruction of Pt NCs.This electrochemically seed-mediated method is also valid for reshaping commercial Pt/C catalyst to create high-index facets,and both mass activity and stability of this catalyst have been enhanced.2.Four different shape samples of Pt nanocrystals(spherical,octahedral,tetrahedral and trioctahedral)were prepared on high ordered graphite(HOPG).The results of fluorescence test showed that the enhancement effect was in the order of trioctahedral>tetrahedral>octahedron>spherical.Both experimental and theoretical calculation results provide evidence to support interesting phenomena that high-index structures,especially step atoms,contribute to enhancing fluorescence signal.3.Using microelectromechanical processing method to design the microelectrode array,and the particles will be isolated by using this method in the conductive substrate.A self-made microelectrode is used to detect particles and make the whole system form a loop.The signals of individual particle of hydrogen evolution and formic acid oxidation were detected by the equipment.High-index platinum particles were successfully synthesized on the HOPG.The oxygen reduction reaction of different particles was carried out by scanning electrochemical cell microscopy(SECCM).It was proved that the oxygen reduction activity of single particles with the same morphology was almostsame.4.Two kinds of carbon microelectrodes were prepared by carbon powder deposition using butane and glass encapsulation.The synthesis conditions of high-index plane particles on microelectrode were explored,and the perfect platinum THH particles were successfully prepared on the microelectrode.In general,THH Pt NCs with a size of sub-10 nm were prepared for the first time and the research field of high-index surfaces of platinum nanoparticles was extended to fluorescence system.The enhanced signal of the fluorescence was detected by the platinum nanoparticles and it is further proved that the step atom has a positive effect on the plasma enhancement.Moreover,we set up the electrochemical detection of single particle platform by ourselves and get some preliminary results.We believe that these results have opened a wider road for the study of high-index crystal surface nanoparticles. |
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