AVS 60th International Symposium and Exhibition
    Surface Science Monday Sessions
       Session SS-MoA

Paper SS-MoA8
Coverage Dependence of Photocatalysis of Trimethyl Acetate on TiO2(110)

Monday, October 28, 2013, 4:20 pm, Room 201 A

Session: Metal Oxides: Reactivity and Catalysis
Presenter: Z.T. Wang, Pacific Northwest National Laboratory
Authors: Z.T. Wang, Pacific Northwest National Laboratory
I. Lyubinetsky, Pacific Northwest National Laboratory
Correspondent: Click to Email
Photocatalysis on titania (TiO2) has attracted much attention due to the potential applications on water splitting and pollutant destructions. Various photocatalytic applications of TiO2 often involve interfaces with carboxylate-anchored organic molecules. From the fundamental point of view, one of the most interesting carboxylate-anchored molecules in probing photochemistry on TiO2 is trimethyl acetate (TMA). We employed the high-resolution scanning tunneling microscopy (STM) to investigate the coverage influence for the TMA photocatalysis on rutile TiO2(110) at 300 K. TMA species were deposited through deprotonative dissociation of trimethylacetic acid (TMAA) on TiO2(110). In the deprotonative process, the dissociated TMAA’s generate an equal amount of TMA’s and hydroxyl groups (OHb) on TiO2(110). We found that TMA’s adsorbed at Ti sites exhibit the same photoreaction (complete hole-induced decomposition) at all coverages but coverage-dependent reaction dynamics, where the reaction rates decrease with increasing TMA coverages. Furthermore, our results reveal that pre-adsorbing hydroxyl groups on TiO2(110) also suppress the TMA photodecomposition. We demonstrate that the coverage-dependence of TMA reaction rates should be attributed to the variation of hydroxyl group concentration on TiO2(110). It appears that OHb species likely being the surface electron-traps decrease TiO2 reactivity toward hole-mediated reactions, which results in the decreasing of TMA photoreaction rates with increasing its coverages.