The impact of metal/oxide interfaces on the catalytic properties of oxide-supported metal nanoparticles is a topic of longstanding interest in the field of heterogeneous catalysis. The significance of the metal/oxide interaction has been shown to vary according to both the inherent reactivity of the metal nanoparticle and the properties of the oxide support, with effects such as the metal d-band center, the nanoparticle shape, and the reducibility of the oxide believed to contribute to the overall system reactivity. In recent years, the water gas shift (WGS) reaction, wherein carbon monoxide and water are converted to carbon dioxide and hydrogen, has emerged as a model chemistry to probe the molecular-level details of how catalysis can be promoted in such environments, and this reaction is the focus of the present contribution. Using a combination of periodic Density Functional Theory calculations and microkinetic modeling, we present a comprehensive analysis of the WGS mechanism at the interface between a quasi-one dimensional platinum nanowire and an irreducible MgO support. The nanowire is lattice matched to the MgO support to remove spurious strain at the metal/oxide interface, and reactions both on the nanowire and at the three-phase boundary itself are considered in the mechanistic analysis. Additionally, to elucidate the consequences of adsorbate–adsorbate interactions on the WGS chemistry, an ab-initio thermodynamic analysis of CO coverage is performed, and the impact of the higher coverage CO states on the reaction chemistry is explicitly evaluated. These results are combined with detailed calculations of adsorbate entropies and dual-site microkinetic modeling to determine the kinetically significant features of the WGS reaction network which are subsequently, validated through experimental measurements of apparent reaction orders and activation barrier. The analysis demonstrates the important role that the metal/oxide interface plays in the reaction, with the water dissociation step being facile at the interface compared to the pure metal or oxide surfaces. Further, explicit consideration of CO interactions with other adsorbates at the metal/oxide interface is found to be central to correctly determining reaction mechanisms, rate determining steps, reaction orders, and effective activation barriers. These results are captured in a closed-form Langmuir–Hinshelwood model, derived from a simplified version of the complete microkinetic analysis, which reveals, among other results, that the celebrated carboxyl mechanism of Mavrikakis and coworkers is the governing pathway when accounting for reaction-relevant CO coverages.

金属/氧化物界面对氧化物负载的金属纳米颗粒的催化性能的影响是非均相催化领域中长期关注的主题。已经表明，金属/氧化物相互作用的重要性根据金属纳米粒子的固有反应性和氧化物载体的性质而变化，并具有诸如金属d-能带中心，纳米颗粒形状和氧化物的还原性被认为有助于整个系统的反应性。近年来，水煤气变换（WGS）反应（其中一氧化碳和水转化为二氧化碳和氢气）已作为一种模型化学方法出现，以探索在这种环境下如何促进催化的分子水平细节，并且该反应是当前贡献的重点。结合周期性密度泛函理论计算和微动力学模型，我们对准一维铂纳米线和不可还原的MgO载体之间的界面处的WGS机制进行了全面分析。纳米线与MgO载体晶格匹配，以消除金属/氧化物界面处的杂散应变，在机理分析中考虑了纳米线上和三相边界本身的反应。另外，为了阐明吸附剂-吸附剂相互作用对WGS化学的影响，对CO的覆盖度进行了从头开始的热力学分析，并明确评估了较高覆盖度的CO状态对反应化学的影响。这些结果与详细的吸附物熵计算和双位微动力学模型相结合，以确定WGS反应网络的动力学显着特征，随后通过表观反应阶数和活化障碍的实验测量对其进行验证。分析表明金属/氧化物界面在反应中起着重要作用，与纯金属或氧化物表面相比，水离解步骤在界面上更容易。此外，发现在金属/氧化物界面处明确考虑CO与其他吸附质的相互作用对于正确确定反应机理，速率确定步骤，反应顺序和有效活化障碍至关重要。这些结果被记录在闭式Langmuir-Hinshelwood模型中，该模型源自完整的微动力学分析的简化版本，该模型显示，除其他结果外，Mavrikakis和同事的著名羧基机理是解释反应的主要途径。相关的CO范围。发现在金属/氧化物界面上明确考虑CO与其他吸附质的相互作用是正确确定反应机理，速率确定步骤，反应顺序和有效活化障碍的关键。这些结果被记录在闭式Langmuir-Hinshelwood模型中，该模型源自完整的微动力学分析的简化版本，该模型显示，除其他结果外，Mavrikakis和同事的著名羧基机理是解释反应的主要途径。相关的CO范围。发现在金属/氧化物界面上明确考虑CO与其他吸附质的相互作用是正确确定反应机理，速率确定步骤，反应顺序和有效活化障碍的关键。这些结果被记录在闭式Langmuir-Hinshelwood模型中，该模型源自完整的微动力学分析的简化版本，该模型显示，除其他结果外，Mavrikakis和同事的著名羧基机理是解释反应的主要途径。相关的CO范围。