The dissociative adsorption of hydrogen sulfide over nanophase titanium dioxide

A variety of TiO₂ materials, including a nanophase TiO₂ powder, were evaluated for their ability to dissociatively adsorb H₂S in a H₂ environment. A temperature programmed desorption technique was used to determine the rate of sulfide accumulation on the surface of the samples as a measurement of initial activity. The initial activity for the gas condensation-produced nanophase TiO₂ with its rutile structure was found to be greater than that for other samples of TiO₂ tested. When normalized for surface area, the initial specific activities of the rutile samples studied for the dissociative adsorption of H₂S were similar in magnitude, but significantly higher than those of the anatase TiO₂ samples investigated. Thus, the improvement in the activity is attributed mainly to the ability of the nanophase synthesis method to produce high surface area rutile TiO₂. When evaluated using x-ray photoelectron spectroscopy, the nanophase TiO₂ was found to be significantly deficient in oxygen. Annealing this material in oxygen decreased the number of anion vacancies and lowered the activity. Thus, we conclude that oxygen vacancies also contribute to the H₂S dissociative adsorption activity.