The interaction between HCHO and TiO2 (101) surface without and with water and oxygen molecules

The interactions between formaldehyde (HCHO) molecule and TiO2 (1 0 1) surface without and with water and oxygen were studied using density functional theory calculations. The adsorption energy of HCHO adsorption on TiO2 surface without water and oxygen is -360.96 kJ/mol, and HCHO molecule is not dissociated. The oxygen and carbon atoms of HCHO are bonded to the titanium and oxygen (O1) atoms of TiO2 surface, respectively, and form a dioxymethylene (CH2O2) structure. The adsorption energy of HCHO adsorption on TiO2 surface system with water and oxygen is -723.40 kJ/mol, and O-2, H2O and HCHO molecules are all dissociated. HCHO molecule not only interacts with TiO2 surface, but also combines with O-2 molecule. Two C-H bonds of HCHO are broken, one hydrogen atom (H1) is bonded to the oxygen atom (O2) of O-2, while another hydrogen atom (H2) is bonded to the O atom (O1) of TiO2 surface. The remaining C-O bond that the dissociated and new formed H-O bonds can be oxidized to form carbon dioxide and water in subsequent action by oxygen from the atmosphere. H2O and O-2 molecules have a great effect on the degradation process of HCHO molecule on TiO2 (1 0 1) surface.