A series of supported WO3/TiO2 catalysts was prepared by a new synthesis procedure involving co precipitation of an aqueous TiO(OH)(2) and (NH4)(10)W12O41*5H(2)O slurry under controlled pH conditions. The morphological properties, surface WO. molecular structures, surface acidity and surface chemistry of the co-precipitated WO3/TiO2 catalysts were determined with BET, in situ Raman, in situ IR, steady-state NO/NH3/O-2 SCR and NO/NH3-temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Time-resolved isotopic O-18-O-16 exchange with IR spectroscopy demonstrated that tungsten oxide was present as surface WO, sites on the TiO2 support with mono-oxo O = WO4 coordination. In contrast to previous studies employing impregnation synthesis that found only surface one mono-oxo O = WO4 site (similar to 1010-1016 cm(-1)) on TiO2, the co-precipitation procedure resulted in the formation of two distinct surface WO. sites: mono-oxo O = WO4 (1012-1014 cm(-1))and a second mono-oxo O = WO4 (similar to 983-985 cm(-1)). The new surface mono-oxo O = WO4 (similar to 983-985 cm(-1)) site is thought to be associated with surface defects on the co-precipitated titania support. The co-precipitated catalysts exhibited slightly enhanced SCR reactivity that is thought to be related to the presence of the new surface O = WO4 sites. Additional factors, however, may also be contributing. This is the first study that attempts to relate the molecular level structural properties of co-precipitated WO3-TiO2 catalysts with their surface reactivity for SCR. (C) 2016 Elsevier B.V. All rights reserved.