Formaldehyde Polymerization on (WO₃)₃/TiO₂(110) Model Catalyst

Polymerization of formaldehyde, H 2 CO, was studied under ultrahigh vacuum conditions on a model catalyst consisting of monodispersed (WO 3 ) 3 clusters anchored on TiO 2 (110). Formaldehyde oligomers, (H 2 CO) n, desorbing from the polymer that formed on the catalyst surface are detected between 250 and 325 K in temperature-programmed desorption experiments. At least two monolayers (ML) of H 2 CO are required on the surface to observe (H 2 CO) n, desorption and the amount saturates for H 2 CO coverages in excess of ∼40 ML. The presence of H 2 CO multilayers is required for the polymerization to take place indicating that it had to occur below 100 K. The saturation amount increases with increasing coverage of (WO 3 ) 3 clusters with the highest amount of ∼13 ML observed on 1.2 (WO 3 ) 3 /nm 2 . No (H 2 CO) n desorption was observed on the bare TiO 2 (110) surface.