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Clean catalysts---Pt@CNT
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http://www.natureasia.com/asia-materials/highlight.php?id=253 Clean catalysts Published online 17 September 2008 The combustion of fossil fuels in automobile engines creates greenhouse gases which have been implicated in global climate change. Polymer electrolyte fuel cells are clean energy alternatives to the combustion engine. These cells use pure hydrogen as a fuel for generating electrical energy to drive cars and the only by-product is water. Notably, platinum acts as a catalyst for the chemical reactions leading to the generation of electricity. Now researchers from China1 report on the potential of using carbon nanotubes decorated with platinum nanocubes for the reduction of oxygen for fuel cell applications. Platinum is expensive and one of the goals of fuel cell research is to maximise the activity of platinum catalysts so as to reduce the amount required for efficient operation. Scientists are increasingly interested in using nanotechnology—controlling the morphology of platinum nanoparticles—to ensure that the most reactive facets of the platinum crystals are exposed to optimise their catalytic performance. Platinum-based catalysts are often deposited on carbon supports, and scientists are investigating how nanostructural control of the carbon support can also improve catalytic performance. Importantly, it is difficult to deposit nanoparticles on nanotubes because of the small size of the components and the curvature of nanotubes. In a one-step process, Yang and colleagues synthsized monodispersed platinum nanocubes of around 6 nm coated with a bilayer of a surfactant, which yielded structures with an overall positive charge. The researchers then produced negatively charged carbon nanotubes by wrapping them in polymer chains. Next, a composite of the two nanomaterials was formed using a layer-by-layer technique where oppositely charged species were alternately deposited onto a flat surface. Finally, the nanotubes and the nanocubes were attracted to each other by electrostatic interactions. Experiments revealed the composites to exhibit excellent catalytic activity for the reduction of oxygen—an important reaction in hydrogen fuel cell operation. The authors say that further improvements in performance could be made by increasing the surface area of catalytically-active nanoparticles facets, removing free surfactant molecules, which could block active sites, and by investigating approaches to prevent platinum nanocube aggregation. Reference Yang, W., Wang X., Yang, F., Yang, C. & Yang, X. Carbon nanotubes decorated with Pt nanocbes by a noncovalent functionalization method and their role in oxygen reduction. Adv. Mater. 20 2579–2587 (2008). Author affiliation Prof. X. Yang, W. Yang, X. Wang, Dr. F. Yang, C. Yang State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry, Chinese Academy of Sciences Changchun, Jilin 130022 (PR China) E-mail: xryang@ciac.jl.cn Prof. X. Yang, W. Yang, X. Wang, Dr. F. Yang, C. Yang Graduate School of the Chinese Academy of Sciences Beijing 100039 (PR China) |
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