Oxidative dehydrogenation of methanol at ceria-supported vanadia oligomers

- Temperature-programmed formaldehyde desorption peaks are assigned to different active sites.
- For the different active sites, pre-exponential factors vary by two orders of magnitude.
- At a ceria-supported V3O6 species, methanol is oxidized with an intrinsic barrier of 133 kJ/mol.
- This ceria-supported V3O6 species is less active than the corresponding VO2 monomer.
- In contrast, silica-supported vanadia oligomers are more active than the corresponding monomers.

We study the adsorption and partial oxidation of methanol at a trimeric VOX species supported on ceria, which was found to be the thermodynamically most stable species under slightly reducing conditions. Results for the oxidation of methanol obtained using dispersion-corrected PBE+U and HSE are compared with a metastable monomeric VO2 species. The intrinsic barriers for monomers (103 kJ/mol), trimers (133 kJ/mol), and the pristine surface (136 kJ/mol) are compared with the corresponding values derived from temperature-programmed desorption experiments, i.e. 100, 125, and 150 kJ/mol, respectively. It was found that the VO2 trimer is more active than the pristine ceria (1 1 1) surface due to entropic effects, showing up in a higher pre-exponential factor. However, the VO2 trimer is less active than the monomer due to structural relaxation in the surface O layer of the latter.

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