催化剂载体的作用和分子在金属氧化物表面吸附的区域选择性：Cu/γ-Al 2 O3上的NO还原
Role of Catalyst Support and Regioselectivity of Molecular Adsorption on a Metal Oxide Surface: NO Reduction on Cu/γ-alumina
摘要：
研究了Cu/γ-Al_2O_3非均相催化剂上NO还原反应中催化剂载体和金属氧化物表面分子吸附区域选择性的作用。对于固体表面，基于分步氢终止（SSHT）方法构建了γ-氧化铝表面的计算模型。悬挂键是通过切割模型的晶体结构而出现的，它被H原子逐步终止，直到模型具有适当的能隙。所得到的SSHT模型具有真实的红外（IR）和紫外-可见（UV/Vis）光谱。用振动耦合密度（VCD）作为反应性指标，对Cu在γ-Al 2 O3上吸附的区域选择性和NO在Cu/γ-Al 2 O3上吸附的区域选择性进行了研究，以取代前线轨道理论不能给出明确结果的缺陷.我们发现，高分散的Cu原子被负载在γ-Al_2O_3表面的Lewis基氧原子上，这就是所谓的锚定效应，位于γ-Al_2O_3表面的四面体位置。γ-Al 2 O3载体的作用是提高Cu催化剂的前线轨道，从而使Cu/γ-Al 2 O3催化剂向NO提供电子反馈。此外，Cu/γ-Al 2 O3催化剂的VCD分布穿透到γ-Al 2 O3载体中，表明NO吸附还原后，多余的反应能消散到载体中。换句话说，支撑件起到热浴的作用。由于Cu-NO键比Cu-O2键强，因此在氧化性气氛中，Cu/γ-Al 2 O3催化剂上的NO还原仍能进行。
英文摘要：
The role of catalyst support and regioselectivity of molecular adsorption on a metal oxide surface is investigated for the NO reduction on a Cu/γ-alumina heterogeneous catalyst. For the solid surface, computational models of the γ-alumina surface are constructed based on the Step-by-Step Hydrogen Termination (SSHT) approach. Dangling bonds, which appear by cutting the crystal structure of a model, are terminated stepwise with H atoms until the model has an appropriate energy gap. The obtained SSHT models exhibit the realistic infrared (IR) and ultraviolet-visible (UV/Vis) spectra. Vibronic coupling density (VCD), as a reactivity index, is employed to elucidate the regioselectivity of the Cu adsorption on the γ-alumina and that of the NO adsorption on the Cu/γ-alumina in place of the frontier orbital theory that could not provide clear results. We discovered that the highly dispersed Cu atoms are loaded on Lewis-basic O atoms, which is known as anchoring effect, located in the tetrahedral sites of the γ-alumina surface. The role of the γ-alumina support is to raise the frontier orbital of the Cu catalyst, which in turn gives rise to the electron back-donation from the Cu/γ-alumina to NO. In addition, the penetration of the VCD distribution of the Cu/γ-alumina into the γ-alumina support indicates that the excessive reaction energies dissipate into the support after the NO adsorption and reduction. In other words, the support plays the role of a heat bath. The NO reduction on the Cu/γ-alumina proceeds even in an oxidative atmosphere because the Cu-NO bond is strongly bounded compared to the Cu-O2 bond.
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