Effect of water on the adsorbed structure of formic acid on TiO2 anatase (1 0 1)

The effect of water on the adsorption of formic acid on the anatase (1 0 1) surface of TiO2 was investigated with density functional theory. These calculations showed that water co-adsorbed with formic acid promotes O–H bond dissociation to produce formate ions, but that the details of this chemistry depend on the surface coverage of formic acid. For 1/4 monolayer (ML) formic acid coverage, O–H dissociation required only a 1:1 ratio of water to formic acid. At 1 ML formic acid coverage, only 1/4 ML formic acid dissociated unless significant constraints were placed on water adsorption geometries. The density functional theory calculations also indicated that water converts bidentate bridging formate to monodentate formate. Comparisons with experimental data reveal that these transformations can have an important influence on elementary steps in the photocatalytic decomposition of formic acid on TiO2 and Pt/TiO2.

Density functional theory calculations showed water co-adsorbed with formic acid promoted O–H bond dissociation on anatase (1 0 1) depending on formic acid and water coverage. The addition of water also stabilized monodentate formate relative to bidentate formate.Figure optionsDownload high-quality image (52 K)Download as PowerPoint slideResearch highlights
► Density functional studies of water/formic acid interactions on TiO2.
► Water promotes formic acid decomposition to formate at low coverage.
► Formic acid dissociation is limited at high coverage.
► Water converts bidentate formate to monodentate formate.