Excess charge driven dissociative hydrogen adsorption on Ti₂O₄⁻

Abstract

The mechanism of dissociative D adsorption on TiO, which serves as a model for an oxygen vacancy on a titania surface, is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations and a recently developed single-component artificial force induced reaction method. TiO readily reacts with D under multiple collision conditions in a gas-filled ion trap held at 16 K forming a global minimum-energy structure (DO-Ti-(O)-Ti(D)-O). The highly exergonic reaction proceeds quasi barrier-free via several intermediate species, involving heterolytic D-bond cleavage followed by D-atom migration. We show that, compared to neutral TiO, the excess negative charge in TiO is responsible for the substantial lowering of the D dissociation barrier, but does not affect the molecular D adsorption energy in the initial physisorption step.

Identification of Active Sites and Structural Characterization of Reactive Ionic Intermediates by Cryogenic Ion Trap Vibrational Spectroscopy

“…Additional IR bands may be observed as a result of symmetry lowering and lifting of degeneracies or of IR‐active combination bands involving the ion‐messenger degrees of freedom . In more severe cases, tagging leads to more substantial structural changes in the core ion or/and an energetic reordering of isomers . Kinetic trapping of isomers upon tagging is also possible .…”

“…[79] In more severe cases, tagging leads to more substantial structural changes in the core ion or/and an energetic reordering of isomers. [80][81][82][83][84] Kinetic trappingo fi somers upon tagging is also possible. [78] Helium is typically the messenger of choice, as it represents the weakestp erturber due to its comparably smallp olarizability.A nion-He complexes are considerably more difficult to form and H 2 /D 2 is typically used as am essengerf or negative ions.…”

“…[78] Helium is typically the messenger of choice, as it represents the weakestp erturber due to its comparably smallp olarizability.A nion-He complexes are considerably more difficult to form and H 2 /D 2 is typically used as am essengerf or negative ions. However,r adical anions may react with molecular hydrogen, [84] in which case the heavi-er noble gas atoms represent ab etter choice.H e-tagging in ion traps was originally demonstrated by Brümmer et al, [37] while efficient H 2 /D 2 taggingo fa nions in ion traps wass hown by Wang and Wang. [38] There are special cases in which helium is not an innocent tag.…”

Experimentelle Bestimmung des aktiven Zentrums im heteronuklearen Redox‐System [AlVOx]+./CO/N2O (x=3, 4) durch Gasphasen‐Infrarotspektroskopie

“…¾hnliche Bindungsgeometrien wurden bereits für [Zr 2 O 4 ] + C, [14] [V 2 O 4 ] + C, [15] [CeVO 4 ] + C, [16] [VPO 4 ] + C, [17] [Al 2 O 4 ] À C [18] sowie [Ti 2 O 4 ] À C [19] gefunden. Der globale Grundzustand von [AlVO 4 ] + C entspricht einem elektronischen Dublett-Zustand, dessen geometrische Struktur aus einem viergliedrigen Ring (V-(m-O) 2 -Al) mit endständigen VO-a nd AlO-Gruppen besteht (Abbildung 1; 1).…”

“…Dazu wurden die IRPD-Spektren der entsprechenden He-und CO-Komplexe dieser Kationen unter Verwendung der intensiven und weit durchstimmbaren IR-Strahlung eines Freie-Elektronen-Lasers (FEL) [12] gemessen und mit den fürv erschiedene Isomere berechneten IR-Spektren verglichen. [13] [14] [V 2 O 4 ] + C, [15] [CeVO 4 ] + C, [16] [VPO 4 ] + C, [17] [Al 2 O 4 ] À C [18] sowie [Ti 2 O 4 ] À C [19] gefunden. Die anderen drei Isomere liegen energetisch um mehr als 100 kJ mol À1 hçher und kommen daher fürd ie Zuordnung zum Grundzustand schon allein aus energetischen Überlegungen nicht infrage.…”