Friday, January 29, 2010

Synthesis of Platinum Cobalt Alloy Nanoparticles Yield Improved Catalyst for Proton Exchange Membrane Fuel Cells


FIG. 4 is a transmission electron microscope (TEM)  image of 4.6 nanometer (nm) sized platinum cobalt (PtCo) alloy nanoparticles used for polymer fuel cell catalyst as produced by  a synthesis process created by SUNY Binghamton researchers
Benchmark Pt catalysts used in the cathode of low temperature fuel cells exhibit high cost, low activity and poor durability, which are some of the major barriers to commercialization of   proton exchange membrane fuel cell technology. Alloy catalysts have the potential to enhance catalytic activity as well as improve durability. Among alloy catalyst compositions, PtCo alloy catalysts have shown recent promise in the laboratory.

A synthesis process for platinum cobalt (PtCo) nanoparticles has been developed by State University of New York (SUNY) Binghamton Professor of Chemistry Chuan-Jian Zhong, and research associates Jin Luo, Zhichaun Xu and Ting He.  The SUNY process provides for synthesis methods to produce alloy nanoparticles with the desired controllable size distribution, dispersion, and composition characteristics, according to U.S. Patent Application 20100018346.

Synthesis of nanoparticles with particle size control is provided by the method of using two different metal-containing precursors, a capping component, an optional reducing agent, and then contacting the two precursors with the capping component to form a reaction solution, which is heated to produce first and second metals-containing nanoparticles. By controlling the ratio of the concentration of the capping component to the total concentration of the two metal-containing precursors, the nanoparticles can have diameters ranging between about 1 nm to about 15 nm. A decrease in the concentration of the capping component typically increases the size of the nanoparticles. Preferred compositions include Pt and Co-containing alloy nanoparticles. Controlled synthesis of larger, about 6 nm to about 12 nm, sized nanoparticles can be achieved in a solvent-free reaction process.

Use of Pt alloy nanoparticles that can increase the catalytic activity and reduce the amount of Pt required is also one of the possible approaches to achieve the same level of cathode performance with a reduced amount of precious metal. Difficulty in controlling the particle size, distribution and compositional uniformity of the nanoparticles are concerns with alloy nanoparticle preparation schemes.  The SUNY process appears to overcome these concerns.

FIG. 6  is a  TEM micrograph of PtCo nanoparticles
FIG. 7 is a TEM micrograph of PtCo nanoparticles supported on carbon.

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