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 H-2 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.