Reactivity of Lattice Oxygens Present in V₂O₅(010):  A Periodic First-Principles Investigation

Abstract

The present paper deals with the periodic first-principles density functional (DFT) calculations on hydrogen adsorption on the V2O5(010) surface. The calculated results reveal that the vanadyl oxygen is the most active site for hydrogen adsorption among the three kinds of structurally different lattice oxygens in terms of their coordination with vanadiums. Our calculated harmonic vibrational frequencies of the three types of OH species are found to correlate with their corresponding bond strengths and support their respective reactivity. It is confirmed that the lattice relaxation contributes to the reactivity of the oxygens significantly in all cases while the local environment of adsorption site affects both the geometry and reactivity of the adsorption system only in the case of tricoordinated oxygen. Hydrogen adsorption at these oxygens reduces the surface in different ways. Comparison of the desorption ability of the OH species from the surface shows that removal of the O1H species, formed by H adsorption at vanadyl oxygen, is energetically preferable. The present work demonstrates that the periodic approach gets rid of the artifacts of the cluster method, and thus, first-principles DFT methodology demonstrates its reliability to investigate geometric, electronic, and catalytic properties of transition metal oxide catalysts.

Reactivity of the V2O5–TiO2-anatase catalyst: role of the oxygen sites

“…It is interesting to note that the bridging V-O-V renders a heat of adsorption of 4.67 eV. The highest reactivity of a terminal oxygen towards atomic hydrogen is also reported in previous theoretical works in bulk V 2 O 5 [4,38] although other authors do not find the same result [39]. Another point of interest is the effect of the support that is not taken into account in these calculations and could provide new sites more reactive.…”

“…A full optimization including the support improves the good match between the V 2 We have analyzed the interaction of atomic hydrogen with the different sites present in the V 2 O 5 /TiO 2 -(001) model [33]. There is a controversy regarding the reactivity of the oxygen sites in the catalyst, some authors attributing it to the terminal [4,38], bridging [5,[50][51][52] or three-fold coordinated [53] sites in the bulk V 2 O 5 structure. The calculated values for the H adsorption on our vanadia/titania model are given in table 1.…”

Adsorption of H2O on the V2O5(010) Surface Studied by Periodic Density Functional Calculations

“…For the investigation of adsorption states with respect to transition-metal-oxide catalysts, our earlier study has confirmed that this methodology is reliable, and it gets rid of the restrictions of cluster approach. 4 The geometries for all the adsorption systems are optimized by CASTEP, which uses a conjugated gradient technique in a direct minimization of the Kohn-Sham energy functional 20 and employs pseudopotentials to represent core electrons. Basis sets used are plane-wave functions.…”

“…Moreover, the proposal concerning that the O 2 is more negatively charged than the O 3 is contrary to the chemical intuition and the theoretical studies. 4,12,14 Therefore, the conclusion inferred by them seems not so reliable. In addition, Moshfegh and Ignatiev 7 have reported that water adsorbs dissociatively on the V 2 O 5 surface through the action of two neighboring vanadium sites of -V 5+ -O-V 4+ -by means of the temperature-programmed desorption technique, and the activation energy is measured to be ca.…”

Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reactant adsorption at vanadium oxide substrate

“…Here, electronic, geometric, and energetic parameters are evaluated using reasonably large cluster models together with density-functional theory (DFT). Going beyond previous theoretical studies [18][19][20][27][28][29][30][31][32][33][34][35] where only sections of the perfect V 2 O 5 surface have been examined, we consider also models for sections of the reduced surface. The latter are simulated by local environments near surface oxygen vacancies which are assumed to being created during the SCR reaction.…”