Abstract
The reaction of formamide over the (0 1 1) faceted TiO2(0 0 1) surface has been studied by Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopy (XPS). Two main reactions were observed: dehydration to HCN and H2O and decomposition to NH3 and CO. The dehydration reaction was found to be three to four times larger than the decomposition at all coverages. Each of these reactions is found to occur in two temperature domains which are dependent upon surface coverage. The low temperature pathway (at about 400 K) is largely insensitive to surface coverage while the high temperature pathway (at about 500 K) shifts to lower temperatures with increasing surface coverage. These two temperature pathways may indicate two adsorption modes of formamide: molecular (via an eta(1)(O) mode of adsorption) and dissociative (via an eta(2)(O,N) mode of adsorption). C1s and N1s XPS scans indicated the presence of multiple species after formamide absorption at 300 K. These occurred at ca. 288.5 eV (-CONH-) and 285 eV (sp(3)/sp(2) Q for the C1s and 400 eV-(NH2), 398 eV (-NH=) and 396 eV (N ) for the N1s and result from further reaction of formamide with the surface. (C) 2009 Elsevier B.V. All rights reserved.