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A new form of platinum, 24-facet nanocrystals, have been produced by an international collaboration. The novel tetrahexahedral particles are four times as effective a catalyst as the industrially important commercial platinum available for oxidising formic acid and ethanol. The work could lead to a more efficient process of catalytic oxidation for the production of hydrogen for fuel cells. "If we are going to have a hydrogen economy, we will need better catalysts," says Zhong Lin Wang of the Georgia Institute of Technology, "This new shape for platinum catalyst nanoparticles greatly improves their activity." The team produced the nanocrystals electrochemically from spherical particles of platinum held on a carbon substrate. They could control the size of the resulting nanocrystals by varying the number of square wave electrical potential cycles applied. "This electrochemical technique is vital to producing such tetrahexahedral platinum nanocrystals," adds team member Shi-Gang Sun of Xiamen University, China, "and may have applications to other catalytic metals." Platinum is commonly used in industrial chemical processing, in motor vehicle catalytic converters, and in fuel cell membranes for electricity production from hydrogen or hydrocarbons. However, commercially available platinum nanocrystals have low-index facets, {100} or {111}, but finding stable, high index structures with {210}, {730} or {520} facets could improve all these applications and lead to novel uses for the metal. The new nanocrystals are high index and remain stable up to 800 Celsius, which means they should be effective as well as recyclable. A downside to the results so far is that the new structures are more than twenty times the size of existing platinum catalysts, so require more metal, which means they have lower activity gram for gram. "We need to find a way to make these nanocrystals smaller while preserving the shape," Wang adds, "If we can reduce the size through better control of processing conditions, we will have a catalytic system that would allow production of hydrogen with greater efficiency." Related links:
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Multifaceted Pt face off |
