1. Adsorption and dissociation of molecular hydrogen on orthorhombic β- Mo2C and cubic δ-MoC (001) surfaces
- Author
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Francesc Illas, Sergio Posada-Pérez, Francesc Viñes, Rosendo Valero, JoséA. Rodriguez, and Universitat de Barcelona
- Subjects
Binding energy ,Ab initio ,Nuclear physics ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Dissociation (chemistry) ,Catalysis ,Carburs ,Adsorption ,Materials Chemistry ,Termodinàmica ,Hidrogenació ,Chemistry ,Dissociació (Química) ,Espectroscòpia infraroja ,Surfaces and Interfaces ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Crystallography ,Physical chemistry ,Thermodynamics ,Density functional theory ,Orthorhombic crystal system ,Física nuclear ,Hydrogenation ,Carbides ,0210 nano-technology ,Dissociation - Abstract
Molybdenum carbides are increasingly used in heterogeneously catalyzed hydrogenation reactions, which imply the adsorption and dissociation of molecular hydrogen. Here a systematic density functional theory based study, including or excluding dispersion terms, concerning the interaction and stability of H2 with cubic δ-MoC(001) and orthorhombic β-Mo2C(001) surfaces, is presented. In the latter case the two possible C or Mo terminations are considered. In addition, different situations for the H covered surfaces are examined. Computational results including dispersive forces predict an essentially spontaneous dissociation of H2 on β-Mo2C(001) independently of the surface termination, whereas on δ-MoC(001) molecular hydrogen dissociation implies a small but noticeable energy barrier. Furthermore, the ab initio thermodynamics formalism has been used to compare the stability of different H coverages. Finally, core level binding energies and vibrational frequencies are presented with the aim to assist the interpretation of yet unavailable data from X-ray photoelectron and infrared spectroscopies.