Platinum Nanoclusters Exhibit Enhanced Catalytic Activity for Methane Dehydrogenation
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- Cheng, Z., Fine, N.A. & Lo, C.S. Top Catal (2012) 55: 345. doi:10.1007/s11244-012-9803-5
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Methane utilization, whether by steam reforming or selective oxidation to produce synthesis gas or alcohols, requires the activation and dissociation of at least one carbon–hydrogen bond. At high temperatures, using platinum nanoparticles as catalysts, this process operates with low activity. However, the catalyst particle shape may be controlled at low temperatures, and faceted particles may catalyze hydrocarbon transformation with increased activity. In this study, we use density functional theory calculations to calculate the thermodynamics of methane dehydrogenation on both (hemi)spherical and tetrahedral platinum nanoclusters. We show all steps of methane dehydrogenation on the hemispherical cluster have high activation barriers (0.4–1.0 eV), thus requiring high temperatures for this process. However, the energy barriers for methane dehydrogenation on the tetrahedral cluster are lower than the corresponding barriers on the hemispherical cluster, and in particular, the dissociation of the methyl group to form methylene and hydrogen has an activation barrier of only 0.2 eV. Thus, we expect that hydrogen production from methane would proceed at a higher rate and conversion on tetrahedral clusters than on hemispherical clusters. The resulting hydrogen and carbon-containing species may then serve as building blocks for the production of chemicals and fuels. We believe that catalyst shape is vitally important in controlling catalytic activity, and the use of faceted catalyst particles opens up possibilities for low-temperature and energy-efficient hydrocarbon transformations.