Metal-oxide interfaces are of great importance in catalytic applications since each material can provide a distinct functionality that is necessary for efficient catalysis in complex reaction pathways. Moreover, the synergy between two materials can yield properties that exceed the superposition of single sites. While interfaces between metals and metal oxides can play a key role in the reactivity of traditional supported catalysts, significant attention has recently been focused on using “inverted” oxide/metal catalysts to prepare catalytic interfaces with unique properties. In the inverted systems, metal surfaces or nanoparticles are covered by oxide layers ranging from submonolayer patches to continuous films with thickness at the nanometer scale. Inverse catalysts provide an alternative approach for catalyst design that emphasizes control over interfacial sites, including inverted model catalysts that provide an important tool for elucidation of mechanisms of interfacial catalytic reactions and oxide-coated metal nanoparticles that can yield improved stability, activity and selectivity for practical catalysts.

This review begins by providing a summary of recent progress in the use of inverted model catalysts in surface science studies, where oxides are usually deposited onto the surface of metal single crystals under ultra-high vacuum conditions. Surface-level studies of inverse systems have yielded key insights into interfacial catalysis and facilitated active site identification for important reactions such as CO oxidation, the water-gas shift reaction, and CO₂ reduction using well-defined model systems, informing strategies for designing improved technical catalysts. We then expand the scope of inverted catalysts, using the “inverse” strategy for preparation of higher-surface area practical catalysts, chiefly through the deposition of metal oxide films or particles onto metal nanoparticles. The synthesis techniques include encapsulation of metal nanoparticles within porous oxide shells to generate core-shell type catalysts using wet chemical techniques, the application of oxide overcoat layers through atomic layer deposition or similar techniques, and spontaneous formation of metal oxide coatings from more conventional catalyst geometries under reaction or pretreatment conditions. Oxide-coated metal nanoparticles have been applied for improvement of catalyst stability, control over transport or binding to active sites, direct modification of the active site structure, and formation of bifunctional sites. Following a survey of recent studies in each of these areas, future directions of inverted catalytic systems are discussed.

金属氧化物界面在催化应用中非常重要，因为每种材料都可以提供独特的功能，这是在复杂反应路径中进行有效催化所必需的。此外，两种材料之间的协同作用可产生超过单个位点叠加的特性。尽管金属与金属氧化物之间的界面可以在传统负载型催化剂的反应性中发挥关键作用，但最近人们的注意力主要集中在使用“转化”氧化物/金属催化剂制备具有独特性能的催化界面上。在倒置系统中，金属表面或纳米颗粒被氧化膜覆盖，氧化膜的范围从亚单层膜片到具有纳米级厚度的连续膜。

这篇综述首先概述了在表面科学研究中使用倒装模型催化剂的最新进展，在这些研究中，氧化物通常在超高真空条件下沉积在金属单晶的表面上。逆系统的表面水平研究已对界面催化产生了重要见解，并促进了重要反应（如CO氧化，水煤气变换反应和CO _2）的活性位点识别使用定义明确的模型系统进行减排，为设计改进的技术催化剂提供信息策略。然后，我们使用“逆向”策略制备高表面积的实用催化剂，主要是通过将金属氧化物膜或颗粒沉积到金属纳米颗粒上，来扩大倒立催化剂的范围。合成技术包括使用湿化学技术将金属纳米颗粒封装在多孔氧化物壳中以生成核壳型催化剂，通过原子层沉积或类似技术施加氧化物外涂层，以及由更常规的催化剂几何形状自发形成金属氧化物涂层在反应或预处理条件下。氧化物包覆的金属纳米粒子已被用于改善催化剂的稳定性，控制转运或结合到活性位点，直接修饰活性位点结构以及形成双功能位点。在对每个领域的最新研究进行了调查之后，对倒置催化系统的未来方向进行了讨论。