Comparative study on the effect of H2 pre-adsorption on CO oxidation in O2-poor atmosphere over Au/TiO2 and TiO2: Temperature programmed surface reaction by a multiplexed mass spectrometer testing

The behaviors of H-2 pre-adsorption on CO oxidation in an O-2-poor stream containing a trace H2O over Au/TiO2 and TiO2 have been investigated by a temperature programmed surface reaction testing, respectively. It was found that the H-2 pre-adsorption could keep CO oxidation without H2O consumption over Au/TiO2, but suppress CO oxidation over TiO2. The chemisorption testing showed that the H-2 adsorption at Au/TiO2 could benefit to the formation of Ti-bonded hydroxyl species (Ti4+-OH), while the H-2 adsorption at TiO2 would consume the Ti-bonded hydroxyl species and form the bridge hydroxyl species (Ti4+-OH-Ti4+). These results show that only the Ti-bonded hydroxyl species (not all kinds of hydroxyl species) could act as the active species of oxidizing CO. Furthermore, it is suggested that the dissociative hydrogen adsorbed at Au sites could activate the lattice oxygen of TiO2 to form the active Ti-bonded hydroxyl species (hydrogen spillover from Au to TiO2), which exhibit a strong reducibility than the H directly adsorbed at TiO2. (C) 2016 Elsevier B.V. All rights reserved.