Abstract

The kinetics and mechanism for temperature programmed reaction following adsorption of an adsorbate can be better understood by simulation and fitting with comparison to experiment. A case study is presented here for the chemistry of adsorption of methanol on a CeO₂(111) surface followed by heating. The gas products observed are CH₃OH, CH₂O, H₂, H₂O, CO, CO₂. At low temperatures (< 500 K), there is formation of H₂ and H₂O, where the H₂O formation is accompanied by lattice oxygen vacancy (V) formation and is thus important in determining the selectivity towards different products. Microkinetic modeling was performed using a recently published method for fitting to gain mechanistic knowledge of the H₂ and H₂O + V formation at < 500 K. In the kinetic models used here, most of the H₂ and H₂O + V formation can be explained by a mechanism in which a metastable state of hydrogen on the surface (H*) acts as an intermediate. Two possibilities were investigated for the source of the metastable H* intermediate: H* from CH bond breaking of methoxies, or promotion of H⁺ to H* via electron transfer from ionic methoxies absorbed in oxygen vacancies (CH₃O⁻/V). From this study, we consider the latter to be more likely at < 500 K. For the H₂O formation, it was found to be critical that H₂O cannot dissociate directly on oxygen vacancies. Catalytic chemistry was observed in simulations, including catalytic formation of oxygen vacancies. Various features of the experimental results were reproduced, including methoxies being the major carbon containing species on the surface at < 500 K.

中文翻译：

---

甲醇在CeO 2（111）：H 2和H 2 O + V生成上的温度程序反应的微观动力学模拟和拟合

抽象的

通过模拟并与实验进行比较，可以更好地理解吸附物吸附后程序升温反应的动力学和机理。本文介绍了一个案例研究，涉及甲醇在CeO ₂（111）表面上的吸附，然后加热的化学过程。观察到的气体产物为CH ₃ OH，CH ₂ O，H ₂，H ₂ O，CO，CO ₂。在低温（<500 K）下会形成H ₂和H ₂ O，其中H ₂O的形成伴随着晶格氧空位（V）的形成，因此对于确定对不同产物的选择性很重要。使用最新发布的方法进行微动力学建模，以拟合获得<500 K时H ₂和H ₂ O + V形成的机理知识。在此处使用的动力学模型中，大多数H ₂和H ₂ O + V形成可以用一种机制来解释，其中表面（H *）上的氢的亚稳态起着中间作用。对于亚稳H *中间体的来源，研究了两种可能性：H *来自甲氧基的CH键断裂，或通过电子从氧空位中吸收的离子型甲氧基的电子转移而将H ⁺促进为H *₃ ø ^- / V）。从这项研究中，我们认为后者在<500 K时更有可能。对于H ₂ O的形成，关键是H ₂ O不能在氧空位上直接解离。在模拟中观察到催化化学，包括氧空位的催化形成。再现了实验结果的各种特征，包括在500 K以下的表面上，主要的含碳物质是methoxy。