Boronic acid adsorption on TiO2 rutile (110): A DFT+U study

Abstract

Surface modification of TiO₂ is crucial in many optoelectronic applications, such as in dye-sensitized solar cells (DSSCs), where anchoring groups facilitate the covalent binding of dye molecules to nanocrystalline TiO₂. Anchoring groups affect the stability of the linkage and the electronic coupling between the semiconductor and dye sensitizer, thus influencing the efficiency of the DSSC. In this study, we explore boronic acids as a novel alternative to commonly used anchoring groups. We investigate the optimization of the stability of boronic acids anchored on the TiO₂ rutile (110) surface through the introduction of various functional groups, specifically methyl, phenyl, and fluorophenyl. This fully computational study employs density functional theory with the DFT+U Hubbard correction and D3 dispersion corrections. A range of molecular and dissociative adsorption structures are analyzed to determine the dominant mode of adsorption. Additionally, adsorption is modeled on multiple surface sizes to assess the impact of surface coverage on adsorbate configuration and adsorption energy. We find that using the larger surface cell is necessary to obtain reliable adsorption energies. The bidentate doubly dissociated configuration is identified as the dominant mode of adsorption. Adsorption is strengthened with the introduction of functional groups, most notably with the phenyl groups. Our findings suggest that boronic acids are a viable alternative to conventional anchoring groups.