Lucci Felicia R, Darby Matthew T, Mattera Michael F G, Ivimey Christopher J, Therrien Andrew J, Michaelides Angelos, Stamatakis Michail, Sykes E Charles H
Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02155, United States.
Thomas Young Centre and Department of Chemical Engineering, University College London , Roberts Building, Torrington Place, London WC1E 7JE, United Kingdom.
J Phys Chem Lett. 2016 Feb 4;7(3):480-5. doi: 10.1021/acs.jpclett.5b02400. Epub 2016 Jan 19.
Key descriptors in hydrogenation catalysis are the nature of the active sites for H2 activation and the adsorption strength of H atoms to the surface. Using atomically resolved model systems of dilute Pd-Au surface alloys and density functional theory calculations, we determine key aspects of H2 activation, diffusion, and desorption. Pd monomers in a Au(111) surface catalyze the dissociative adsorption of H2 at temperatures as low as 85 K, a process previously expected to require contiguous Pd sites. H atoms preside at the Pd sites and desorb at temperatures significantly lower than those from pure Pd (175 versus 310 K). This facile H2 activation and weak adsorption of H atom intermediates are key requirements for active and selective hydrogenations. We also demonstrate weak adsorption of CO, a common catalyst poison, which is sufficient to force H atoms to spill over from Pd to Au sites, as evidenced by low-temperature H2 desorption.
氢化催化中的关键描述符是H₂活化的活性位点性质以及H原子在表面的吸附强度。利用稀Pd-Au表面合金的原子分辨模型系统和密度泛函理论计算，我们确定了H₂活化、扩散和解吸的关键方面。Au(111)表面的Pd单体在低至85 K的温度下催化H₂的解离吸附，这一过程此前预计需要连续的Pd位点。H原子位于Pd位点，并在比纯Pd显著更低的温度下脱附（分别为175 K和310 K）。这种容易的H₂活化和H原子中间体的弱吸附是活性和选择性氢化的关键要求。我们还证明了常见催化剂毒物CO的弱吸附，这足以迫使H原子从Pd溢流到Au位点，低温H₂脱附证明了这一点。
