Collaborative Research: Experimental and theoretical study on the structure and catalytic activity of metal cluster/metal oxide interfaces

目前最成功的金属/金属氧化物催化剂是将高度分散、低浓度的金属原子嵌入金属氧化物表面。负载在氧化铈上的钯金属是高活性催化剂的一个重要例子，可作为汽车三元催化剂、催化燃烧催化剂和固体氧化物燃料电池负极材料。这些金属/金属氧化物催化剂的活性可以由支撑表面结构独特地控制。此外，这些低浓度金属催化剂具有显著的抗烧结性能，这是一种常见的多组分催化剂降解机制，因此表明它们具有优越的抗加热/冷却循环和氧化还原环境变化的能力。然而，活性位点的结构很难在原子尺度上定义。对于金属-铈（M/CeO2）催化体系，在反应条件下发生动态重构，铈和金属结构都改变了反应活性。那么如何解释钯对铈的催化行为和性能呢？三位研究者，宾夕法尼亚州立大学的A.C. van Duin和m.j. Janik以及南佛罗里达大学的m.m. Batzill假设Ce1-xPdxO2-d的混合表面氧化物可能在某些反应条件下提供具有高活性和稳定性的独特活性位点。为了证实这一点，并为了充分开发Pd/CeOx和类似金属/金属氧化物催化剂的潜力，他们认为，Pd/ceria系统需要详细的、原子尺度的催化转化机制和与底-表面相互作用相关的表面动力学知识。在一项合作研究中，pi建议利用反应力场（ReaxFF）和密度泛函理论（DFT）方法的原子模拟以及实验表面科学研究来研究Pd/CeO2体系的动态结构和反应性。结合表面科学和ReaxFF/DFT方法将提供Ce1-xPdxO2- Ô？的结构，稳定性和活性的详细测定。非混合氧化物表面。这将有助于回答有关该催化剂体系的问题。从更广泛的角度来看，将实验和计算相结合的方法应用于这种复杂的催化体系将促进对可还原性氧化物载体对催化剂稳定性和活性影响的基本理解，并为制备高活性M/CeO2催化剂提供指导。此外，开发了一个集成的双组件仿真环境，并通过实验验证了该环境的有效性。这种模拟和实验之间的合作将为未来的催化研究提供路线图；这里开发的计算工具是普遍适用的，从而为其他催化材料提供了直接的扩展。该研究项目还将教育和外展活动紧密结合。具体来说，在PSU，将引入原子尺度模拟方法的工程师课程，并辅以实验技术的讲座和教程。

1033000BatzillThe most successful metal/metal oxide catalysts currently available involve highly-dispersed, low-concentration metal atoms embedded in a metal oxide surface. Palladium metal supported on cerium oxide, is an important example of a highly active catalyst, with applications as an automotive three-way catalyst, in catalytic combustion, and as a solid oxide fuel cell anode material. The activity of these metal/metal oxide catalysts can be uniquely controlled by the support surface structure. Furthermore, these low-concentration metal catalysts have demonstrated significant resistance against sintering, a common multi-component catalyst degradation mechanism, thus indicating superior resistance to heating/cooling cycles and changes in redox enviroment. However, the structure of the active site is challenging to define at the atomistic scale. For the metal-ceria (M/CeO2) catalytic system, dynamic restructuring occurs under reaction conditions and both the ceria and metal structure alter reactivity. So how then to explain the catalytic and performance behaviors of Pd on ceria? Three Investigators, A.C. van Duin and M. J. Janik of Pennsylvania State University and M. M. Batzill of the University of South Florida, hypothesize that mixed surface oxides of Ce1-xPdxO2-d may provide unique active sites with high activity and stability under certain reaction conditions. To confirm this and in order to fully develop the potential of Pd/CeOx and similar metal/metal oxide catalysts, they believe a detailed, atomistic-scale knowledge of the catalytic conversion mechanisms and the surface dynamics related to substrate-surface interactions is required for the Pd/ceria system. In a collaborative study, the PIs propose to utilize atomistic simulation with Reactive Force-Field (ReaxFF) and Density Functional Theory (DFT) approaches together with experimental surface science studies to investigate the dynamic structure and reactivity of Pd/CeO2 systems. The combined surface science and ReaxFF/DFT approach will provide detailed determination of the structure, stability, and activity of Ce1-xPdxO2-?Ô?nmixed oxide surfaces. This will help answer questions about this catalyst system.From the broader perspective, the combination of experimental and computational approaches applied to this complex catalytic system will advance the fundamental understanding of the effect of reducible oxide supports on catalyst stability and activity, as well as provide guidance towards the preparation of highly active M/CeO2 catalysts. Further, the development of an integrated, two-component simulation environment, which is validated against experiment is the outcome of this project. This collaboration between simulation and experiment will provide a roadmap for future catalytic research; the computational tools developed here are generally applicable, thus providing straightforward extension to other catalytic materials.The research program also closely integrates education and outreach activities. Specifically, at PSU, courses for engineers on atomistic-scale simulation methods will be introduced, which will be complemented by lectures and tutorials on experimental techniques.