γ-Alumina is widely used as an oxide support in catalysis, and palladium nanoparticles supported by alumina represent one of the most frequently used dispersed metals. The surface sites of the catalysts are often probed via FTIR spectroscopy upon CO adsorption, which may result in the formation of surface carbonate species. We have examined this process in detail utilizing FTIR to monitor carbonate formation on γ-alumina and zirconia upon exposure to isotopically labelled and unlabelled CO and CO2. The same was carried out for well-defined Pd nanoparticles supported on Al2O3 or ZrO2. A water gas shift reaction of CO with surface hydroxyls was detected, which requires surface defect sites and adjacent OH groups. Furthermore, we have studied the effect of Cl synthesis residues, leading to strongly reduced carbonate formation and changes in the OH region (isolated OH groups were partly replaced or were even absent). To corroborate this finding, samples were deliberately poisoned with Cl to an extent comparable to that of synthesis residues, as confirmed by Auger electron spectroscopy. For catalysts prepared from Cl-containing precursors a new CO band at 2164 cm-1 was observed in the carbonyl region, which was ascribed to Pd interacting with Cl. Finally, the FTIR measurements were complemented by quantification of the amount of carbonates formed via chemisorption, which provides a tool to determine the concentration of reactive defect sites on the alumina surface.

中文翻译：

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CO在（Pd-）Al2O3和（Pd-）ZrO2上的吸附和反应：碳酸盐形成的振动光谱。

γ-氧化铝被广泛用作催化中的氧化物载体，并且氧化铝负载的钯纳米粒子是最常用的分散金属之一。通常在吸附CO时通过FTIR光谱探测催化剂的表面部位，这可能导致形成表面碳酸盐物质。我们已经详细研究了该过程，利用FTIR监测暴露于同位素标记和未标记的CO和CO2时γ-氧化铝和氧化锆上碳酸盐的形成。对负载在Al2O3或ZrO2上的定义明确的Pd纳米颗粒也进行了同样的处理。检测到CO与表面羟基的水煤气变换反应，这需要表面缺陷位点和相邻的OH基团。此外，我们研究了Cl合成残基的作用，导致碳酸盐的形成大大减少，并且OH区域发生变化（孤立的OH基团被部分置换，甚至不存在）。为了证实这一发现，通过俄歇电子光谱法证实，样品故意被Cl中毒至与合成残留物相当的程度。对于由含氯前体制备的催化剂，在羰基区域观察到2164 cm-1处的新CO带，这归因于Pd与Cl相互作用。最后，通过对通过化学吸附形成的碳酸盐的数量进行定量来补充FTIR测量，这提供了一种确定氧化铝表面反应性缺陷部位浓度的工具。如俄歇电子能谱法所证实，样品被故意用Cl毒化至与合成残留物相当的程度。对于由含氯前体制备的催化剂，在羰基区域观察到2164 cm-1处的新CO带，这归因于Pd与Cl相互作用。最后，通过对通过化学吸附形成的碳酸盐的数量进行定量来补充FTIR测量，这提供了一种确定氧化铝表面反应性缺陷部位浓度的工具。如俄歇电子能谱法所证实的，样品被故意用Cl毒化至与合成残留物相当的程度。对于由含氯前体制备的催化剂，在羰基区域观察到2164 cm-1处的新CO带，这归因于Pd与Cl相互作用。最后，通过对通过化学吸附形成的碳酸盐的数量进行定量来补充FTIR测量值，这为确定氧化铝表面反应性缺陷部位的浓度提供了一种工具。