Controllable Synthesis Of Pt-based Bimetallic (Pt/M, M:Fe, Co, Ni) Catalytically Active Nanoparticles

Special attention has been focused on platinum and its alloys due to their excellent physical and chemical properties in catalysis, magnetic storage, nanodevices, and biotechnology. Among various applications, their implementation as catalysts in the production of hydrogen from methane, in automobile catalytic converters, and particularly in the proton-exchange membrane fuel cells (PEMFC) has stimulated considerable interests. Although Pt has been extensively studied in various structures, it is too expensive for many applications and at the same time highly susceptive to carbon monoxide poisoning especially for room temperature operations. Accordingly, the development of highly efficient Pt-based alloy nanocatalysts has emerged as the most promising solution. In particular, the addition of non-precious transition metals such as Fe, Co, Ni to the Pt lattices is expected to significantly improve their catalytic activities, because these alloy nanostructures often allow unusual arrangement of surface atoms which will tune the d-band state of Pt.Herein we successfully synthesized CoPt,FePt and NiPt nanoparticles via a facile chemical co-reduction method at moderate temperature. By means of TEM (Transmission Electron Microscopy),HRTEM (High Resolution Transmission Electron Microscopy),XRD (X-ray Diffraction),SAED(Select Area Electron Diffraction),EDS (Energy Dispersive X-Ray Spectrum) and electrochemical workstation, the particle size, crystal structure and electrocatalytic properties of these nanoparticles have been studied. The obtained results are as follows:(1) CoPt nano-electrocatalysts with an interesting flowerlike structure were successfully synthesized. This particular architecture of CoPt showed superior performance during the electrooxidation of methanol and formic acid as compared with the commercial Pt/C catalyst from Johnson Matthey (Pt/C-JM). Compared with PtRu, here the addition of Co atoms could simultaneously improve the anti-poisoning effect and increase the overall catalytic efficiency. Considering that Co is much less noble than Ru, these CoPt nanoflowers should have great potential in various electrocatalytic applications.(2) Using the same process, FePt alloy catalysts with two different compositions were prepared and their electrocatalytic performances were tested. The as-synthesized FePt with more Fe atoms has chemically disordered fcc structure and can be transformed into the chemically ordered fct structure after annealing in H₂ at 800℃for 2 hours. We can obtain a multifunctional nanostructure by etching the sample in H₂SO₄.(3) NiPt alloy catalysts were also fabricated using this method and their potential application in fuel cells was evaluated.