Effect of surface modification with H2S and NH3 on TiO2 for adsorption and photocatalytic degradation of gaseous toluene

This study investigates the effects of surface modification with H2S and NH3 respectively on the photocatalytic activity of TiO2 for toluene degradation. Surface modification with H2S was observed to enhance the adsorption of toluene and promote the degradation rate at the start of photocatalytic degradation, while that with NH3 inhibited the adsorption of toluene but enhanced the photocatalytic activity for the toluene degradation. By a combination of in situ DRIFTS and other characterization methods, the adsorption mechanism and relationship between surface structure and photocatalytic activity were proposed. For TiO2-H2S, the sulfhydryl group, which is formed from the dissociation of H2S molecules, could easily interact with toluene. The low photocatalytic activity may be caused by the inhibition of the regeneration of surface hydroxyl groups, poor generation of O2(-center dot) radicals and accumulation of highly stable intermediates. For TiO2-NH3, steric hindrance serves as interference to the adsorption of toluene, while the abundant surface hydroxyl groups are possibly conducive to the degradation of toluene. (C) 2015 Elsevier B.V. All rights reserved.