Chemisorption of CO, NO, and H 2 on transition metal-titania thin film model catalysts

Abstract

Chemisorption on thin film models of Rh TiO 2 and Pt TiO 2 catalysts before and after encapsulation with TiO x (1.0 ⩽ x ⩽ l.2) is reported. TiO x blocks adsorption sites and induces new desorption states. A CO desorption peak, assigned to CO on Rh atoms perturbed by TiO x , is observed at 325 K after adsorption at 120 K on a TiO x -covered Rh TiO 2 surface. CO adsorbed at 285 K onto the encapsulated Rh TiO 2 surfaces shows a new 685 K CO desorption state attributed to an activated form of CO with a weakened CO bond. NO desorbs from clean Rh overlayers with a profile most like Rh(110). On encapsulated Rh surfaces N 2O is the major desorption product. Compared to bulk Pt, desorption experiments show suppressed H 2 adsorption capacity for thin (<2 ML) Pt layers in contact with, but not encapsulated by, TiO x . For thin layers of Pt on fully oxidized TiO 2 layers there is no reduction of H 2 Chemisorption. The results suggest bonding between Ti and Pt which affects H 2 Chemisorption even though no Pt surface sites are blocked.