CAREER: Uncertainty Quantification in the Rational Design of Bifunctional Catalysts

智能优点对于具有多个关键表面中间体的复杂反应，双功能多相催化剂比传统的单相催化剂具有显著的优势，因为每一相都可能被独立地调整以激活关键的反应步骤。遗憾的是，多相催化剂的活性和选择性主要由界面和邻近环境决定，我们对其的理解仍然相对较差。南卡罗来纳大学的Andreas Heyden在这项教师早期职业发展(Career)计划奖中建议利用计算研究来建立这种双功能多相催化剂的基础科学，其活性在很大程度上由气相、可还原氧化物载体和贵金属簇或纳米颗粒的三相边界(TPB)决定。这项工作将集中于确定以二氧化铈和二氧化钛为载体的金和铂催化剂用于水-气变换(WGS)反应的独特活性的来源或描述因素。人们希望更好地了解TPB的化学反应，是因为大多数多相催化剂由几个固相组成，尽管人们通常知道催化剂的整体活性和选择性是多相效应的结果，但对多相体系的化学功能的了解相对较差。考虑到催化剂体系的复杂性，将理论计算与实验观察联系起来对多相体系来说是非常具有挑战性的。海登建议使用现代密度泛函，并量化基于反应网络的计算预测中的不确定性。因此，可以做出现实而有意义的概率预测，这极大地促进了理论计算与实验观测的联系。海登计划使用现代贝叶斯统计工具来验证反应站点模型，并确定给定预测所需的精度水平。通过与普渡大学和南加州大学的科学家合作，获得了用于比较的实验信息。更广泛的影响了解WGS的氧化物负载贵金属催化剂的来源和识别独特活性的描述符，有可能导致开发用于移动和固定应用的改进的WGS催化剂。此外，由于可还原氧化物载体和贵金属的组合催化了许多反应，因此从这项研究中获得的见解很可能应用于各种化学反应。此外，量化计算催化预测中的不确定性的计算策略的应用不仅对在TPBS发生的反应很重要，而且对发生在较低温度下的大多数复杂反应也很重要，因为即使是反应能量的微小误差也会导致预测的周转频率、表观活化势垒和反应顺序的很大不确定。建议项目的研究结果将被整合到研究生和本科生联合选修课？多尺度建模：从电子到化学反应？作为化学工程核心课程的一部分，促进主动、探究式学习。将与当地一所城市高中的工程学院(92%的非裔美国学生)建立一个持续的外联方案，以增加未被充分代表的少数群体参与工程学的学习。该项目的主要内容包括客座讲座、南加州大学学院学生的实践学习体验，以及为工程学院学生提供的指导计划。

Intellectual Merit For complex reactions with more than one key surface intermediate, bifunctional multiphase catalysts have a significant advantage over conventional monophase catalysts since each phase can potentially be adjusted independently to activate a key reaction step. Unfortunately, our understanding of multiphase catalysts whose activity and selectivity is primarily determined by the interfaces and adjacent surroundings remains relatively poor. Andreas Heyden of the University of South Carolina in this Faculty Early Career Development (CAREER) Program Award proposes utilizing computational studies to establish the underlying science of such bifunctional heterogeneous catalysts whose activity is largely determined by the three-phase boundary (TPB) of a gas-phase, a reducible oxide support, and a noble metal cluster or nanoparticle. The work will focus on identifying the origin or descriptors of the unique activity of Au and Pt catalysts supported on ceria and titania for the water-gas shift (WGS) reaction. The desire to better understand chemical reactions at the TPB is motivated by the fact that most heterogeneous catalysts consist of several solid phases and that although the overall catalyst activity and selectivity is often known to be a result of multiphase effects, the understanding of the chemical function of multiphase systems is relatively poor.Given the complexity of catalyst systems, connecting theoretical calculations to experimental observations becomes extremely challenging for multiphase systems. Heyden proposes to usemodern density functionals and to quantify uncertainty in the computational predictionsbased on a network of reactions. As a result, realistic and meaningful probabilistic predictionscan be made which significantly facilitates connecting theoretical calculations with experimentalobservations. Heyden plans to use modern Bayesian statistical tools to validate reaction sitemodels and to identify a required level of accuracy for a given prediction. Experimental information for comparison is secured through collaborations with scientists at Purdue University and the University of Southern California.Broader Impact Understanding the origin and identifying descriptors for the unique activity of oxide supported noble metal catalysts for the WGS has the potential to lead to the development of improved WGS catalysts for mobile and stationary applications. Furthermore, insights obtained from this study can likely be applied to various chemical reactions since the combination of reducible oxide supports and noble metals catalyze many reactions. In addition, the application of a computational strategy that quantifies uncertainty in computational catalysis predictions is important not only for reactions occurring at TPBs but for most complex reactions occurring at lower temperatures where even small errors in reaction energies lead to large uncertainties in predicted turnover frequencies, apparent activation barriers, and reaction orders.The research results of the proposed project will be integrated into a joint graduate and undergraduate elective ?Multiscale Modeling: From Electrons to Chemical Reactors? as part of the core chemical engineering curriculum to promote active, inquiry based learning. A continuous outreach program will be established with the Engineering Academy of a local urban high school (92% African American students) to increase the participation of underrepresented minorities in the study of engineering. Key components of this program include guest lectures, hands-on learning experiences of Academy students onthe USC campus, and a mentoring program for Engineering Academy students.