Abstract
Identification and characterization of peroxo species (-O-O- and -O-O-H), which has been proposed to accumulate on surfaces during photocatalytic water splitting and hence inhibit the reaction rate, is important to understand this catalytic process. In this study, peroxo species were prepared and characterized on model TiOx/Rh(111) systems. The TiOx/Rh(111) systems were prepared by chemical vapor deposition of TiOx on Rh(111) using titanium tetraisopropoxide (TTIP - (Ti[OCH(CH3)(2)](4))) as a precursor for TiO2 and characterized with Auger electron spectroscopy. Peroxo species were obtained by exposing the TiOx/Rh(111) systems to H2O2 at 300 K and characterized by infrared reflection absorption spectroscopy (IRRAS) and temperature programmed desorption (TPD). Peroxo species formed on both TiOx clusters and films on Rh(111) decompose completely by 700 K. In order to study their possible reactions, alkenes (ethylene, propylene and cyclooctene, separately) were co-dosed and the surface was subsequently heated at different temperatures. No evidences for the formation of reaction intermediates were observed by IRRAS. TPD experiments of the same systems further confirmed the absence of epoxidation products between the peroxo species and adsorbed olefins.