Langmuir. 2018 Mar 27;34(12):3742-3754. doi: 10.1021/acs.langmuir.7b03360. Epub 2018 Mar 12.
Exploration of catalyst structure and environmental sensitivity for C-O bond scission is essential for improving the conversion efficiency because of the inertness of CO. We performed density functional theory calculations to understand the influence of the properties of adsorbed water and the reciprocal action with oxygen vacancy on the CO dissociation mechanism on ZnGeO(010). When a perfect surface was hydrated, the introduction of HO was predicted to promote the scission step by two modes based on its appearance, with the greatest enhancement from dissociative adsorbed HO. The dissociative HO lowers the barrier and reaction energy of CO dissociation through hydrogen bonding to preactivate the C-O bond and assisted scission via a COOH intermediate. The perfect surface with bidentate-binding HO was energetically more favorable for CO dissociation than the surface with monodentate-binding HO. Direct dissociation was energetically favored by the former, whereas monodentate HO facilitated the H-assisted pathway. The defective surface exhibited a higher reactivity for CO decomposition than the perfect surface because the generation of oxygen vacancies could disperse the product location. When the defective surface was hydrated, the reciprocal action for vacancy and surface HO on CO dissociation was related to the vacancy type. The presence of HO substantially decreased the reaction energy for the direct dissociation of CO on O- and O-defect surfaces, which converts the endoergic reaction to an exoergic reaction. However, the increased decomposition barrier made the step kinetically unfavorable and reduced the reaction rate. When HO was present on the O-defect surface, both the barrier and reaction energy for direct dissociation were invariable. This result indicated that the introduction of HO had little effect on the kinetics and thermodynamics. Moreover, the H-assisted pathway was suppressed on all hydrated defect surfaces. These results provide a theoretical perspective for the design of highly efficient catalysts.
探索 C-O 键断裂的催化剂结构和环境敏感性对于提高转化率至关重要，因为 CO 具有惰性。我们进行了密度泛函理论计算，以了解吸附水的性质及其与氧空位的相互作用对 ZnGeO(010)上 CO 解离机制的影响。当完美表面水合时，HO 的引入被预测会通过两种模式促进断裂步骤，这取决于其出现的方式，其中通过离解吸附的 HO 促进作用最大。离解的 HO 通过氢键降低 CO 解离的势垒和反应能，从而预激活 C-O 键，并通过 COOH 中间体辅助断裂。具有双齿结合 HO 的完美表面比具有单齿结合 HO 的表面更有利于 CO 解离，因为前者的离解 HO 直接促进了反应，而后者的单齿 HO 则通过 H 辅助途径促进了反应。由于氧空位的产生可以分散产物位置，因此具有缺陷的表面对 CO 分解表现出比完美表面更高的反应性。当缺陷表面水合时，空位和表面 HO 对 CO 解离的相互作用与空位类型有关。HO 的存在大大降低了 O-和 O 缺陷表面上 CO 直接解离的反应能，将内禀反应转化为放能反应。然而，分解势垒的增加使反应动力学不利，并降低了反应速率。当 O 缺陷表面上存在 HO 时，直接解离的势垒和反应能都保持不变。这一结果表明，HO 的引入对动力学和热力学几乎没有影响。此外，在所有水合缺陷表面上，H 辅助途径都受到抑制。这些结果为设计高效催化剂提供了理论视角。
