The Mechanism of the Interaction Between Dodecylbenzene Sulfonate and TiO2 Surfaces—DFT Study

To elucidate the microscopic adsorption mechanism of dodecylbenzenesulfonate (DBS−) on the surface of anatase TiO2, this study was conducted based on density functional theory, using the DMol3 module for calculations. Four representative initial configurations including orientation differences in sulfonate, the benzene ring, and the alkyl chain were constructed. The contribution of each functional fragment to adsorption stability and interfacial electron transfer behavior were investigated through geometric optimization, energy calculation, Mulliken population, molecular electrostatic potential analysis, Fukui function, and density-of-states analysis. The results showed that configuration a-101 exhibited a lying orientation and multi-stage synergetic adsorption, with the largest adsorption energy (−210.29 kJ/mol), and it was the most stable configuration. The sulfonate group had the most negative electrostatic potential, and the highest occupied orbital was mainly located on its oxygen atom (O). Additionally, the f− value of the Fukui function of O was the highest, serving as the key electrophilic reaction active site, and formed a Ti-O coordination bond with surface Ti4+. The benzene ring acted as an electron acceptor and participated in adsorption through π-d weak coupling. Adsorption induced the transfer of an about 0.7 e charge from DBS− to TiO2. The 2p orbitals of O and the 3d orbitals of Ti overlapped in the range of −5.0~0.45 eV, forming a coordination bond.