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.