NO and NO2 Adsorption on Al2O3 and Ga Modified Al2O3 Surfaces: A Density Functional Theory Study
NO and NO2 Adsorption on Al2O3 and Ga Modified Al2O3 Surfaces: A Density Functional Theory Study
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DOI：
10.1021/jp907925w
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发表时间：
2010-03-18
影响因子：
3.7
通讯作者：
Junaid, Abu S. M.
中科院分区：
文献类型：
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作者：
Liu, Zhiming;Ma, Lingling;Junaid, Abu S. M.
Al_2O_3及其负载型金属催化剂广泛应用于脱硝催化，但其催化活性中心的性质和结构与活性的关系尚不清楚。通过一系列系统和比较的计算，利用密度泛函理论研究了NO和NO2在Al2O3和Ga改性的Al2O3表面上的吸附以及NO氧化生成硝酸盐的过程.结果表明，NOx、NO和NO2气体优先吸附在（110）面上，并以不同的晶面取向。NO_2在（110）表面上的吸附是以双齿构型进行的，而NO在（110）表面上的吸附是以N-down取向进行的，这使得NO_2在（110）表面上的净电荷转移量大大增加，N-O键也明显伸长。Ga改性的Al_2O_3（110）表面促进了NO和NO_2的吸附和活化。此外，Ga改性的Al2O3（110）表面通过NO氧化形成硝酸盐的活化能势垒（NOx的选择性催化还原的关键过程）比原始Al2O3（110）表面低约35%。这是Ga2O3-Al2O3催化剂选择性催化还原NOx的高活性的原因之一。
Al2O3 and its Supported metal catalysts are widely used in deNO(x), catalysis, but the true nature of the catalytic sites and the structure-activity relationships are Still Unclear. By a set of systematic and comparative calculations, this study investigates the adsorption of NO and NO2, and nitrate formation via the oxidation of NO on Al2O3 and Ga modified Al2O3 surfaces using density functional theory. It is found that NOx, gases (NO and NO2) preferentially adsorb on (110) planes, and are oriented in different Configurations. While NO bonds with the (110) Surfaces through an N-down orientation, the most stable mode of adsorption of NO2 oil the (110) Surfaces is a bidentate configuration, Causing much higher net charge transfer from the Surface and noticeable elongation of the N-O bond. Both the NO and NO2 adsorption and activation are promoted oil the Ga modified Al2O3 (110) Surface. Moreover, the activation energy barrier for nitrate formation via NO oxidation, a process Crucial for the selective catalytic reduction of NOx, is about 35% less oil the Ga modified Al2O3 (110) Surface compared to the pristine Al2O3 (110) Surface. This is one of the reasons for the high activity of Ga2O3-Al2O3 catalyst for the selective catalytic reduction of NOx.