Carboxylate Adsorption on Rutile TiO2(100): Role of Coulomb Repulsion, Relaxation, and Steric Hindrance

• Published in: Journal of physical chemistry. C Vol. 125; no. 25; pp. 13770 - 13779
• Main Authors: Nadeem, Immad M, Hargreaves, Laura, Harrison, George T, Idriss, Hicham, Shluger, Alexander L, Thornton, Geoff
• Format: Journal Article
• Language: English
• Published: American Chemical Society 01.07.2021
• Subjects: C: Chemical and Catalytic Reactivity at Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.1c00892

Understanding the adsorption and photoactivity of acetic acid and trimethyl acetic acid on TiO2 surfaces is important for improving the performance of photocatalysts and dye-sensitized solar cells. Here we present a structural study of adsorption on rutile TiO2(100)-1 × 1 and -1 × 3 using Scanning Tunnelling Microscopy and Density Functional Theory calculations. Exposure of both terminations to acetic acid gives rise to a ×2 periodicity in the [001] direction (i.e., along Ti rows), with a majority ordered c(2 × 2) phase in the case of the 1 × 1 termination. The DFT calculations suggest that the preference of c(2 × 2) over the 2 × 1 periodicity found for TiO2(110)-1 × 1 can be attributed to an increase in interadsorbate Coulomb repulsion. Exposure of TiO2(100)-1 × 1 and -1 × 3 to trimethyl acetic acid gives rise to largely disordered structures due to steric effects, with quasi-order occurring in small areas and near step edges where these effects are reduced.