Infrared studies of CO adsorption on reduced and oxidized [formula omitted

Abstract

Carbon monoxide adsorption experiments were studied on reduced and oxidized Pt TiO 2 with FT-IR. On reduced samples two kinds of linear CO species were observed and assigned as adsorption on Pt close-packed (terrace) sites (2094 cm −1) and on Pt open (step) sites (2077 cm −1). In addition a bridged CO species was found at 1854 cm −1. Both linear species show increasing frequencies with coverage. Saturation CO uptake decreases with increasing substrate reduction temperature and there is a preferential decrease of linear CO species on terrace sites and the concentration of bridged species lies below detection limits. On oxidized Pt TiO 2 samples, some Pt atoms are covered with oxygen atoms and the density of step sites is enhanced. On these surfaces there are two kinds of linear CO species assigned to terraces (2130 cm −1) and steps (2101 cm −1) and a bridged CO species at 1880 cm −1. In addition, several CO species are found which are also detected on reduced samples. These species show intensity variations during lengthy exposures. Preadsorbed linear CO species (2130, 2094, and 2077 cm −1 bands) on oxidized samples are also sensitive to H 2 exposures.