In Situ FT-IR Spectroscopic Study of CO2 and CO Adsorption on Y2O3, ZrO2, and Yttria-Stabilized ZrO2

In situ FT-IR spectroscopy was exploited to study the adsorption of CO 2 and CO on commercially available yttria-stabilized ZrO 2 (8 mol % Y, YSZ-8), Y 2 O 3 , and ZrO 2 . All three oxides were pretreated at high temperatures (1173 K) in air, which leads to effective dehydroxylation of pure ZrO 2 . Both Y 2 O 3 and YSZ-8 show a much higher reactivity toward CO and CO 2 adsorption than ZrO 2 because of more facile rehydroxylation of Y-containing phases. Several different carbonate species have been observed following CO 2 adsorption on Y 2 O 3 and YSZ-8, which are much more strongly bound on the former, due to formation of higher-coordinated polydentate carbonate species upon annealing. As the crucial factor governing the formation of carbonates, the presence of reactive (basic) surface hydroxyl groups on Y-centers was identified. Therefore, chemisorption of CO 2 most likely includes insertion of the CO 2 molecule into a reactive surface hydroxyl group and the subsequent formation of a bicarbonate species. Formate formation following CO adsorption has been observed on all three oxides but is less pronounced on ZrO 2 due to effective dehydroxylation of the surface during high-temperature treatment. The latter generally causes suppression of the surface reactivity of ZrO 2 samples regarding reactions involving CO or CO 2 as reaction intermediates.