First principle study of HF molecule adsorption on TiO2 (110) surface

Titanium and its alloy components are one of the most important technological materials, which has found extensive application in various industries. However, surface defects play a key role in the mechanical properties of these components. Currently, wet chemical etching is one of the most important procedure for surface processing due to the presence of HF since it can etch metal oxide. Therefore, there still a need to investigate the etching mechanism. In this work, adsorption of HF on TiO2(110) surface has been studied using density functional theory to investigate the fundamental process of etching. HF molecule is adsorbed on the TiO2 surface by dissociation to form Ti-F and O-H species. The interaction between HF and TiO2surface become more favorable at high HF coverage. The pre-adsorbed of water molecule is favorable for HF adsorption process, which is in good agreement with experimental results. Fluorination processes show the formation and desorption of water intermediate at 0.50 ML coverage. We also investigated the relation between the work function and Mulliken charge for HF adsorption. The results indicate that the interaction of F on the surface attracts electrons due to its higher electronegativity than oxygen. Our results suggest that adsorption of HF is considered chemisorption process.