Adsorption and Reactions on TiO₂: Comparison of <i>N</i>,<i>N</i>-Dimethylformamide and Dimethylamine

Abstract

Fourier transform infrared spectroscopy has been employed to study the adsorption and reactions of N, N -dimethylformamide (DMF) and dimethylamine (DMA) on powdered TiO 2 . DMF can be adsorbed in molecular form with the carbonyl interacting with the surface Lewis site (Ti 4+ ) or in dissociative form of OCN(CH 3 ) 2 . Theoretical adsorption study of rutile (110) points out that the C* and O atoms of OC*N(CH 3 ) 2 are bonded at a two-fold-coordinated O site and a five-fold-coordinated Ti site, respectively. The thermal products of DMF/TiO 2 are found to be CO and DMA. Photochemical reaction of DMF on TiO 2 in O 2 generates CO 2, HCOO, and NCO. O 2 participates in the reaction with its oxygen atoms incorporated into the three products. DMA can be adsorbed in molecular form and imine species on TiO 2 . Photoirradiation of DMA/TiO 2 in O 2 generates CO 2, HCOO, NCO, and imine species. Interestingly, DMF and OCN(CH 3 ) 2 are produced after postirradiation thermal treatment of DMA on TiO 2, possibly from the reaction between residual DMA and HCOO photoproduct.