In Situ FT-IR Spectroscopic Study of CO and CO Adsorption on YO, ZrO, and Yttria-Stabilized ZrO.

In situ FT-IR spectroscopy was exploited to study the adsorption of CO and CO on commercially available yttria-stabilized ZrO (8 mol % Y, YSZ-8), YO, and ZrO. All three oxides were pretreated at high temperatures (1173 K) in air, which leads to effective dehydroxylation of pure ZrO. Both YO and YSZ-8 show a much higher reactivity toward CO and CO adsorption than ZrO because of more facile rehydroxylation of Y-containing phases. Several different carbonate species have been observed following CO adsorption on YO 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 most likely includes insertion of the CO 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 due to effective dehydroxylation of the surface during high-temperature treatment. The latter generally causes suppression of the surface reactivity of ZrO samples regarding reactions involving CO or CO as reaction intermediates.