Imaging Water Dissociation onTiO2(110)

Abstract

Scanning tunneling microscopy has been used to identify the adsorption site of H(2)O on TiO(2)(110)-(1 x 1) at 150 K, and to monitor the site of the dissociation products at 290 K. Water adsorbs onto the rows of fivefold coordinated Ti atoms at 150 K, dissociating by 290 K to form bridging but not terminal hydroxyls. This points to the involvement of bridging O vacancies in the dissociation pathway.

Water adsorption on rutile TiO2(110) for applications in solar hydrogen production: A systematic hybrid-exchange density functional study

“…13,22 The majority of experimental work supports the view that molecular adsorption dominates in the first layer of water ( 1 ML) on nearly perfect surfaces at low temperatures (<350 K), and that water dissociates only at oxygen vacancy sites. [23][24][25][26][27][28][29][30][31][32][33] The evidence for this picture includes ultraviolet photoelectron spectroscopy (UPS) measurements by Kurtz et al 23 of the nearly perfect (110) surface, which was interpreted in terms of molecular adsorption at monolayer coverage (1 ML) at 160 K, dissociative adsorption at low coverage (∼0.1 ML) at 300 K, and suggested that the rate of dissociation is higher on defective surfaces. Two other UPS studies indicated dissociative adsorption at low coverage, but deduced that dissociation occurred only at oxygen vacancy defect sites.…”

“…As a sequel, the conclusions made from experimental studies vary notably in relation to the extent of dissociation on the nearly perfect surface at various temperatures. 23,27,31 An alternative interpretation of this evidence, and, in particular, of the HREELS spectrum, was developed on the basis of firstprinciples molecular dynamics. 34 In the calculated hydrogen vibrational power spectrum, both water bond-bending δ(HOH) and O-H stretching v(OH) signals were present.…”

Adsorption of acetic and trifluoroacetic acid on the TiO2(110) surface

“…The basic physical and electronic structure of the most stable ͑110͒ surface has been well studied both experimentally 5,6 and theoretically, [7][8][9][10][11] and now, many investigations focus on defected surfaces, especially oxygen vacancies, [12][13][14] adsorption, 10,[15][16][17] or even adsorption onto defected surfaces. 18 -20 Due to their particular relevance to catalysis, many studies have also investigated the properties of adsorbed carboxylic ͑RCOOH͒ acids on the TiO 2 (110) surface.…”

Probing equilibrium of molecular and deprotonated water on TiO 2 (110)

“…As such, bridging hydroxyl groups formed by water dissociation in oxygen vacancy defects interfere with determining the extent of dissociation on regular Ti sites (3,(14)(15)(16)(17)(18)(19). A number of recent studies by a variety of techniques including X-ray photoelectron spectroscopy (XPS) (20), infrared reflection absorption (21), photoelectron diffraction (PhD) (22), and scanning tunneling microscopy (STM) (23)(24)(25) arrived at conflicting conclusions. Whereas the XPS and PhD studies concluded partial dissociation of water in the hydrogenbonded chains on Ti sites at higher coverages (20,22), others are in favor of molecular bonding (21,25).…”