Collaborative Research: Modifying oxide surfaces with functional atomic-layers for nano-engineered catalysts

合作研究：利用纳米工程催化剂的功能原子层修饰氧化物表面金属氧化物的化学和热稳定性使其成为恶劣环境下的理想材料，也是燃料电池或化学品精炼等应用中作为催化剂的载体金属的理想材料。在某些条件下，氧化物载体在化学过程中起着积极的作用，在这种情况下，了解氧化物的性质对于开发新的催化体系和确定它们的工作方式是至关重要的。在高氧压下，金属催化剂颗粒可以氧化并与其氧化物载体反应，形成混合金属氧化物表面层，形成一个与在块状材料上观察到的非常不同的系统。在南佛罗里达大学和宾夕法尼亚州立大学的这项合作项目中，Batzill、Janik和Van Duin博士将敏感的表面表征技术与计算建模方法结合起来，预测由氧化物载体上沉积的过渡金属氧化形成的混合金属氧化物表面的形成。他们预测了多相氧化催化中的氧化物相稳定性和反应活性，并在此过程中发现了一些具有有趣和优异的化学催化性能的新催化材料。该研究项目为高中生、本科生和研究生提供培训机会，并与布鲁克海文国家实验室建立合作关系。此外，该项目正在与现有的大学项目合作，以增加未被充分代表的科学和工程高级学位学生的数量。通过这一奖项，化学系的高分子、超分子和纳米化学(MSN)计划资助南佛罗里达大学的Batzill博士和宾夕法尼亚州立大学的Janik和van Duin博士进行表面受限混合金属氧化物相的研究。多相催化剂中后过渡金属的氧化相是某些氧化反应的活性相。这些氧化物相与另一种金属氧化物载体的相互作用有可能导致新的混合表面相，为氧化物载体上的过渡金属提供额外的可调氧化还原功能。在这个项目中，将单原子层的氧化过渡金属(如Pd，Co，Ni)负载在热力学上更稳定的氧化物(如氧化锌，二氧化钛)上，并探索它们的稳定性和化学功能。结合先进的第一性原理密度泛函理论方法和反应力场(ReaxFF)蒙特卡罗模拟的新进展，使它们能够跨越长度和时间尺度，达到在不同氧化学势的气体环境中描述这些复杂体系的条件。可靠的计算工具对于筛选支持这种新型单层催化剂的材料体系是必不可少的，然后合成并进行实验研究。采用脉冲激光沉积法在不同的氧化环境下制备了单晶氧化物样品。用最先进的扫描探针显微镜方法研究了单层氧化物，并用改进的分子束实验探索了它们的化学功能。预测计算工具与实验验证的结合为定量描述新的单原子层、化学活性氧化物相的形成提供了一个框架。该研究项目为高中生、本科生和研究生提供培训机会，并与布鲁克海文国家实验室建立合作关系。此外，该项目与现有的大学课程合作，以增加未被充分代表的理工科高级学位学生的数量。

Collaborative Research: Modifying oxide surfaces with functional atomic-layers for nano-engineered catalystsThe chemical and thermal stability of metal oxides make them ideal materials for harsh environments and for supporting metals as catalysts in applications such as fuel cells or refinement of chemicals. Under some conditions, the oxide support plays as active role in the chemical process, and in this case understanding the oxide properties is crucial for developing new catalytic systems and determining how they work. Under high oxygen pressure, the metal catalyst particles can oxidize and react with their oxide support to form a mixed metal oxide surface layer to create a system that is very different than that observed on bulk materials. In this collaborative project between the University of South Florida and Pennsylvania State University, Drs. Batzill, Janik and Van Duin are coupling sensitive surface characterization techniques with computational modeling methods that predict the formation of mixed metal oxide surfaces formed by oxidizing transition metals deposited on oxide supports. They predict the oxide phase stability and reactivity in heterogeneous oxidation catalysis, and in the process discover some new catalytic materials with interesting and superior chemical catalytic properties. This research project provides training opportunities for students at high school, undergraduate and graduate levels, and establishes collaborations with Brookhaven National Laboratory. Furthermore, the project is working with existing University programs to increase the number of underrepresented science and engineering advanced degree students.With this award, the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Chemistry Division is funding Dr. Batzill of the University of South Florida and Drs. Janik and van Duin of Pennsylvania State University for the investigations of surface-confined mixed-metal oxide phases. The oxide phase of late transition metals in heterogeneous catalysts are the active phase for certain oxidation reactions. The interaction of these oxide phases with another metal oxide support has the potential to lead to novel mixed surface phases that provide additional tunable redox functionality for transition metals supported on oxides. In this project, single atomic layers of oxidized transition metals (e.g. Pd, Co, Ni) are supported on thermodynamically more stable oxides (e.g. ZnO, TiO2) and their stability and chemical functionalities are explored. Combining advanced first principles density functional theory methods with new developments in reactive force field (ReaxFF) Monte Carlo simulations enables them to span length- and time-scales to reach conditions relevant for describing these complex systems in gas environments of various oxygen chemical potentials. Reliable computational tools are essential for screening of materials systems that support the kind of novel monolayer catalysts that then are synthesized and studied experimentally. Single crystalline oxide samples are prepared by pulsed laser deposition under various oxidation environments. The monolayer oxides are investigated with state-of-the-art scanning probe microscopy methods and their chemical functionality probed by a modified molecular beam experiment. Integration of predictive computational tools with experimental verification provides a framework for a quantitative description of the formation of novel single atomic layer, chemically-active oxide phases. This research project provides training opportunities for students at high school, undergraduate and graduate levels, and establishes collaborations with Brookhaven National Laboratory. Furthermore, the project works with existing University programs to increase the number of underrepresented science and engineering advanced degree students.