Infrared studies of adsorbed species of H2, CO and CO2 over ZrO2

Abstract

The adsorption and reaction of H₂, CO, CO₂, OH(a)+ CO(g) and CO₂(a)+ H₂(g) have been studied in detail by infrared spectroscopy. Hydrogen is dissociatively adsorbed to form the OH and the Zr—H species and CO is weakly adsorbed as the molecular form. The infrared spectrum of adsorbed species of CO₂ over ZrO₂ shows three main bands at ca. 1550, 1310 and 1060 cm^–1 which can be assigned to the bidentate carbonate species. The reaction of OH(a)+ CO(g) at 373 K gave rise to formate and bidentate carbonate species, and after having introduced hydrogen onto this system at 473 K, methoxide species appeared. When hydrogen was introduced over CO₂-preadsorbed ZrO₂, formate and methoxide species also appeared. It is concluded that the formation of the formate and methoxide species results from the hydrogenation of bidentate carbonate species.