Adsorption and Thermal Decomposition of 2-Chloroethyl Ethyl Sulfide on TiO₂ Surfaces

Abstract

The adsorption, desorption, and oxidative decomposition of the 2-chloroethyl ethyl sulfide molecule (2-CEES) has been investigated on the TiO2(110) surface as well as on high area anatase and rutile powdered samples. A combination of measurement tools has been employed. It has been found that a monolayer of 2-CEES desorbs in the temperature range from 275 to 400 K with an activation energy of 105 kJ/mol. Weak repulsive interactions are measured in the monolayer. The molecule may be oxidized both by Ti−OH groups on anatase or rutile and by lattice oxygen in the TiO2. Attack at the C−S bonds occurs as chloroethoxy and ethoxy groups are produced. At about 570 K these species further oxidize to form adsorbed COO and CO3 species. The involvement of lattice oxygen in these reactions near 600 K has been observed by measurements of the background level in the infrared spectrum that may be used to measure the formation of trapped electron states at Ti3+ centers formed when adsorbate oxidation occurs by consumption...