Coverage dependent adsorption behavior of MEA on TiO2(110) and its effect on work function

Abstract

The adsorption of monoethanolamine (MEA) on rutile TiO2(110) surface is important for the application on photo-electric devices through the reduction of the work function of TiO2(110). Thus, we studied coverage-dependent adsorption behavior of MEA on defective and pristine TiO2(110) surfaces and its effect on work function (Ф) by density functional theory (DFT) calculation. The adsorption energy (ΔEads) was calculated with various configurations of MEA molecule. The most stable adsorption was found to be the dissociative adsorption of MEA in gauche configuration at the oxygen vacancy site (ΔEads = -3.604 eV). Also, the work-function drop was the most efficient with this configuration (ΔФ = -1.132 eV). In case of the pristine TiO2(110) surface, MEA adsorbed on Ti5f rows with gauche or dissociative gauche configuration showed relatively high adsorption energies. Therefore, after oxygen vacancies were fully occupied by MEA, Ti5f rows will be occupied by gauche or dissociative gauche configurations of MEA. It was found that the work function of pristine TiO2(110) surface gradually decreased with increasing coverage of MEA for both gauche and dissociative gauche forms.