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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Infrared Study of a Novel Acid-Base Site on ZrO_2 by Adsorbed Probe Molecules. I. Pyridine, Carbon Dioxide, and Formic Acid Adsorption
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Infrared Study of a Novel Acid-Base Site on ZrO_2 by Adsorbed Probe Molecules. I. Pyridine, Carbon Dioxide, and Formic Acid Adsorption

机译：吸附探针分子对ZrO_2上新的酸碱位点的红外研究。 I.吡啶，二氧化碳和甲酸的吸附

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The adsorption of pyridine, carbon dioxide (CO_2), AND FORMIC acid (HCOOH) on various types of surface sites of ZrO_2, vacant sites (for example: bare surface Zr~(4+)O~(2-) ions), and those modified by terminal (t-) and bridged (b-) OH as well as t- and b-methoxy (OCH_3) groups, has been studied by infrared (IR) spectroscopy. The selective reaction of CO_2 with the t-OH group at 213 K and the adsorption of pyridine to replace the t-OH group on ZrO_2 at 273-573 K confirms that t-HO-Zr site possesses acidic and basic properties. Moreover, the nucleophilic substitution adsorption of pyridine occurs more actively at the t-HO-Zr site than that at the vacant t-site on ZrO_2. At 523 K, HCOOH reacts with basic t-OH or t-OCH_3 species before the b-OH or -b-OCH_3 species. The selective reaction of HCOOH with t- and b-OCH_3 groups on ZrO_2 disappears at 573 K. The high activity of t-HO-Zr sites is attributed to relatively stronger Lewis acidic sites generated by releasing t-OH groups in the adsorption, and is also related to the high reactivity of t-OH groups. The Zr ions or t-OH groups at t-HO-Zr sites can play different roles in the adsorption of HCOOH, CO_2 and pyridine, leading to its distinguishable features from those on vacant and b-OH sites. On the other hand, the OCH_3 species at 573 K is supposed to be movable during the adsorption, resulting in the disappearance of the difference in reactivity of t- and b-OCH_3 groups in the adsorption of HCOOH to replace OCH_3 on ZrO_2.
机译：吡啶，二氧化碳（CO_2）和甲酸（HCOOH）在ZrO_2的各种类型的表面位点，空位（例如：裸露的Zr〜（4+）O〜（2-）离子）和通过红外（IR）光谱研究了那些由末端（t-）和桥连（b-）OH以及叔-和b-甲氧基（OCH_3）基团修饰的化合物。 CO_2与213 K处的t-OH基团发生选择性反应，并在273-573 K处吸附吡啶以取代ZrO_2上的t-OH基团，这证明t-HO-Zr位点具有酸性和碱性。此外，吡啶的亲核取代吸附比在ZrO_2的空位t-HO-Zr位更活跃。在523 K，HCOOH与碱性t-OH或t-OCH_3物种先于b-OH或-b-OCH_3物种发生反应。 HCOOH与ZrO_2上的t-和b-OCH_3基团的选择性反应在573 K时消失。还与t-OH基团的高反应性有关。 t-HO-Zr位点上的Zr离子或t-OH基团在HCOOH，CO_2和吡啶的吸附中可以发挥不同的作用，从而使其与空位和b-OH位点上的特征区分开。另一方面，假设在573 K处的OCH_3物种在吸附过程中是可移动的，从而导致HCOOH吸附ZrO_2上的OCH_3时，t-和b-OCH_3基团的反应性差异消失了。

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