First Principles Analysis of H₂O Adsorption on the (110) Surfaces of SnO₂, TiO₂ and Their Solid Solutions

Abstract

Both associative and dissociative H2O adsorption on SnO2(110), TiO2(110), and Ti-enriched Sn1-xTixO2(110) surfaces have been investigated at low (1/12 monolayer (ML)) and high coverage (1 ML) by density functional theory calculations using the Gaussian and plane waves formalism. The use of a large supercell allowed the simulation at low symmetry levels. On SnO2(110), dissociative adsorption was favored at all coverages and was accompanied by stable associative H2O configurations. Increasing the coverage from 1/12 to 1 ML stabilized the (associatively or dissociatively) adsorbed H2O on SnO2(110) because of the formation of intermolecular H bonds. In contrast, on TiO2(110), the adsorption of isolated H2O groups (1/12 ML) was more stable than at high coverage, and the favored adsorption changed from dissociative to associative with increasing coverage. For dissociative H2O adsorption on Ti-enriched Sn1-xTixO2(110) surfaces with Ti atoms preferably located on 6-fold-coordinated surface sites, the analysis of the Wannier centers showed a polarization of electrons surrounding bridging O atoms that were bound simultaneously to 6-fold-coordinated Sn and Ti surface atoms. This polarization suggested the formation of an additional bond between the 6-fold-coordinated Ti-6c and bridging O atoms that had to be broken upon H2O adsorption. As a result, the H2O adsorption energy initially decreased, with increasing surface Ti content reaching a minimum at 25% Ti for 1/12 ML. This behavior was even more accentuated at high H2O coverage (1 ML) with the adsorption energy decreasing rapidly from 145.2 to 101.6 kJ/mol with the surface Ti content increasing from 0 to 33%. A global minimum of binding energies at both low and high coverage was found between 25 and 33% surface Ti content, which may explain the minimal cross-sensitivity to humidity previously reported for Sn1-xTixO2 gas sensors. Above 12.5% surface Ti content, the binding energy decreased with increasing coverage, suggesting that the partial desorption of H2O is facilitated at a high fractional coverage.

Thermodynamic Stability of SnO2Nanoparticles: The Role of Interface Energies and Dopants

“…The present results on heat of adsorption for pure tin dioxide are very consistent with data reported in the literature. 28 36 no apparent systematic trend was observed as a function of Mn concentration. That is, the adsorption curves show crossovers along the studied coverage range, such that the integral values become quite similar.…”

A computational study on water adsorption on Cu2O(111) surfaces: The effects of coverage and oxygen defect

“…Using GGA + U, molecular water adsorption is preferred on Cr 2 O 3 (0 0 0 1) at the lowest coverage, and isoenergetic molecular and dissociative adsorption is found at high coverage, and the rather low dissociation barrier (0.12 eV) allows proton exchanges between the OH groups from ab initio MD simulation [51]. Dissociative H 2 O adsorption is found on SnO 2 (1 1 0) from the lowest to monolayer coverage [52].…”

The Kinetic Parameters of the Oxygen Evolution Reaction (OER) Calculated on Inactive Anodes via EIS Transfer Functions:•OH Formation

“…Most computational efforts have been focused on the atomistic level, where the "activity" or "inactivity" with respect to the OER has been quantified using density functional theory (DFT). [18][19][20][21][22] To this concern, theoretical studies of inactive (BDD, SnO 2 -Sb and PbO 2 ) and active (IrO 2 and RuO 2 ) anodes revealed that this reactive trend is a tradeoff between the adsorption energies for H 2 …”