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Monomeric (VO2+) and dimeric mixed valence (V2O33+) vanadium species at the surface of shape controlled TiO2 anatase nano crystals

2022; Elsevier BV; Volume: 406; Linguagem: Inglês

10.1016/j.jcat.2021.12.029

1090-2694

Valeria Lagostina, Eleonora Romeo, Anna Maria Ferrari, Valter Maurino, Mario Chiesa,

Polyoxometalates: Synthesis and Applications

• The coordination of vanadyl species on the different facets of TiO 2 anatase is resolved. • Tetrahedrally coordinated vanadyl ions at the TiO 2 (1 0 1) surface and square pyramidal vanadyls at the (0 0 1) termination are identified by DFT. • The existence of dinuclear V 4+ -O-V 5+ mixed valence structures is confirmed by ENDOR/HYSCORE techniques. • 17 O surface enrichment provides insights in the metal-oxide bond interaction through 17 O hyperfine interactions. Metal atoms and ions at well-defined anatase TiO 2 crystals with exposed (1 0 1) and (0 0 1) facets represent a promising platform for fundamental studies in catalysis using model systems of high complexity for the development of novel catalytic systems exhibiting higher than usual activities. Herein, we report the geometric and electronic structures of supported paramagnetic vanadium catalysts obtained by reaction of VCl 4 vapours with shape controlled anatase TiO 2 supports with preferential (1 0 1) and (0 0 1) facets. Electron Paramagnetic Resonance (EPR) spectroscopy and Density Functional theory (DFT) calculations reveal the presence specific monomeric (VO 2+ ) and dimeric mixed valence (V 2 O 3 3+ ) species with molecular structures dependent on the TiO 2 surface termination.