Characterization of Surface and Photooxidative Properties of Supported Metal Oxide Photocatalysts Using Solid-State NMR

Abstract

Photocatalytic oxidation reactions were carried out in sealed 5 mm glass NMR tubes at room temperature. All samples were In situ solid-state NMR (SSNMR) methodologies have been used to investigate the surface properties and photooxidative reactivities of a number of metal oxide photocatalysts. Adsorption of ethanol on single monolayers of TiO2, SnO2, V2O5, and WO3 supported on porous Vycor glass results in the formation of hydrogen-bonded ethanol species and metal-bound ethoxide species. The chemical shift of the metal-bound ethoxide species varies with the metal oxide catalyst while the chemical shift of the hydrogen-bonded species is independent of the metal oxide. X-ray powder diffraction, UV-VIS spectroscopy, and SSNMR investigations of ethanol adsorption show that increasing the number of monolayers of TiO2 on the Vycor surface changes the morphology of the catalyst from amorphous at a single monolayer coverage to anatase at a four monolayer coverage. The rate of photocatalytic oxidation of ethanol, acetone, and 2-propanol also increases with increasing TiO2 monolayer coverage.

Organically hybridized SnO2 gas sensors

“…It is well known that the hydrogen bonding is formed between surface hydroxyl groups of oxides and organic compounds containing heteroatoms with the lone pair electrons [18][19][20][21]. The SnO 2 surface modification by organic components with hydroxyl groups could lead the formation of hydrogen bonding between them.…”

Organically Hybridized SnO2 Sensors for Selective Detection of Gas Molecules

“…It is well known that the hydrogen bonding is formed between surface hydroxy groups of oxides and organic compounds containing heteroatoms with the lone pair electrons [16][17][18]. As the XPS measurement of the APS-SNO2 film proved the existence of hydroxy groups on the SnO2 surface, the amino groups of the organic components could lead the formation of hydrogen bonding to the surface hydroxy groups.…”

Photocatalytic properties of mesoporous TiO2/ZrO2 films in gas-phase oxidation of alcohols

“…2. a) Change in rates of photocatalytic oxidation of aliphatic alcohols r on TiO 2 /ZrO 2 films as a function of ZrO 2 content: 1) methanol; 2) isopropanol; 3) ethanol; b) photocatalytic oxidation of ethanol (1-6) and acetaldehyde (7,8) in the gas phase on pure TiO 2 (1, 7) and on TiO 2 /ZrO 2 films: 2) 5% ZrO 2 ; 3), 8) 10% ZrO 2 ; 4) 15% ZrO 2 ; 5) 20% ZrO 2 ; 6) 30% ZrO 2 .…”

“…We know [2,8] that photocatalytic oxidation of ethanol can occur by two mechanisms: through a step of formation of the gaseous intermediate acetaldehyde, which is desorbed as an intermediate product mainly from the sites of weak ethanol adsorption [7], or via decomposition of the adsorbed substrate with formation of gaseous and adsorbed formate and acetate structures. The first route occurs with physical adsorption of ethanol molecules on the surface of the titanium dioxide, while the second route occurs with dissociative adsorption of ethanol.…”

“…Development of template synthesis methods has made it possible to obtain powders and films of TiO 2 with an extended surface area and a porous structure [3,4], which is especially important for carrying out photocatalytic oxidation of volatile organic compounds, in particular ethylene [5], acetone [6], and ethanol [2,7,8], which are potential air pollutants at industrial sites. An effective method for increasing the photocatalytic activity of titanium dioxide is also incorporation of transition metal and noble metal ions into a titanium dioxide matrix [9].…”