Peptide Mediated Synthesis Of Pt-Pd Bimetallic Nanostructures And Their Applications

In recent years,small organic molecule fuel cells have attracted lots of interests among the scientists and engineers,due to their high efficiency,low energy consumption,easy to carry and environment friendly property.Among the metal catalysts having been studied so far,Pt-based catalysts have shown high catalytic activity and good conductive ability in this field.However,the nanoparticles are apt to aggregate during reaction,which reduces the catalytic activity rapidly.One-dimensional platinum nanocatalysts（1D Pt nonocatalysts）can resist aggregation and erosion efficiently because of its morphology and self-supported structure.Therefore,shape-controlled synthesis of 1D Pt-based nanocatalysts is a hot spot recently.In addition,the introduction of a second or even third metals into the Pt-based nanocatalysts can’t only reduce the cost,but also improve the catalytic activities,such as low oxidation over potential,better ability of oxygen reduction.Many efforts have been paid on Pt-based bimetallic nanocatalysts.In the synthesis of 1D Pt nanocatalysts,peptides are used as templates because of selectable diversity and adjustable sequence.In this thesis,we choose Ac-IIIK-NH₂（I₃K）self-assembly as the template,and synthesized Pt or PtPd nanostructures with different morphologies and catalytic activities through controlling the reduction process of metallic precursors.In this thesis,we first reviewed the studies of crystal growth,the influence factors of crystal morphology,the application of Pt-based nanocatalysts.Self-assembly of peptide I₃K was used as template in nanocatalyst synthesis,which carries positive charges on the surface when pH is about 6⁷.K₂PtCl₄ was adopted as the metal precursor,and Pt-based nanocatalysts with different morphologies were synthesized with different reductants（NaBH₄,HCOOH,VC,N₂H₄）.Then catalytic activities,including resist CO in the methanol oxidation,were assessed and compared with commercial Pt/C catalyst.1D Pt nanowires have been synthesized using HCOOH and NaBH₄ as the reductants,And the catalytic activity of 1D Pt-based nanocatalyst reduced by NaBH₄ is much better than commercial Pt/C.When changing metal precursors（K₂PtCl₄,K₂PtCl₆,H₂PtCl₆）with different Pt valence and hydrolysis ability,1D Pt nanostructures have also been synthesized with NaBH₄ as the reducing agent.Transmission electronic microscope and high-resolution transmission electronic microscope showed that the Pt nanocrystals have Pt{111}lattice face.The catalytic activity of the synthesized nanocatalysts are higher than that of commercial Pt/C,and the catalyst with K₂PtCl₄ as metal precursor has the best catalytic activity.We also adopted Pd as the second metal components in the Pt-based nanocatalysts,precursor and varied the ratio of K₂PtCl₄ and K₂PdCl₄ with 4:1,3:1,3:2 and 1:1（Pt/Pd atom ration）,and prepared 1 D Pt-Pd bimetallic nanocatalysts.In the assessment of the catalytic activity to methanol anodic oxidation and oxygen reduction reaction,we found that when the ratio of Pt/Pd is 1:1,CO poisoning resistance was much higher than the single Pt or Pd catalysts,and the catalytic activity of oxygen reduction was higher than the commercial Pt/C catalyst,the introduce of Pd have increased the mass activity of Pt.All in all,we improved the catalytic activity of nanocatalysts by changing the kinds of reductants,precursor and ratio of precursors.