DFT study on the interaction of HCHO molecule with S-doped TiO2 (001) surface without and with water and oxygen molecules

Abstract The interactions of formaldehyde (HCHO) molecule with S-doped anatase TiO2 (001) surface without and with water and oxygen were studied by density functional theory (DFT). The adsorption energy of HCHO adsorption on S-doped TiO2 surface with water and oxygen (−709.62 kJ/mol) is much larger than that without water and oxygen (−312.14 kJ/mol). For HCHO adsorption system without water and oxygen, one C –H bond of HCHO molecule is broken. The oxygen and carbon atoms of HCHO are bonded to the titanium and sulfur atoms of S -TiO2 surface, respectively, and form a CH2OS structure. For the system with water and oxygen, H2O and HCHO molecules are both dissociated. HCHO molecule not only interacts with TiO2 surface, but also combines with O2 molecule. Two C –H bonds of HCHO are broken, one hydrogen atom (H1) is bonded to the sulfur atom (S) of TiO2 surface doping, while another hydrogen atom (H2) is bonded to the O atom (O2) of O2 molecule. The remaining C –O bond can be oxidized to form CO2 in subsequent action by oxygen from the atmosphere. The surface doping of sulfur have significant impact on the degradation of HCHO molecule on anatase TiO2 (001) surface with H2O and O2.