EAGER: Imaging of Element-Specific 3D Distribution Dynamics in Working Bimetallic Catalysts by in situ Anomalous Small-Angle X-Ray Scattering

在化学系化学测量与成像(CMI)计划和化学催化(CAT)计划的支持下，坦普尔大学的孙教授正在开发一种实时成像工具，以基于X射线散射的原子分辨率绘制化学元素的空间分布。他与国家实验室同步辐射光源的科学家密切合作，寻找技术解决方案，为催化反应期间催化剂的结构-活性关系提供新的见解。在手术条件下，实时达到所需的成像分辨率存在很大风险。然而，如果成功，孙教授的工作成果可能有助于指导高效催化剂的设计和合成，这是一个重要的研究领域，可能会在许多行业产生重大影响，从炼油厂到制药发现再到燃料电池。国家实验室使用最先进的大型设施，将学生培养成一个重要领域的专家，这在典型的化学家S的技能组合中并不多见。更广泛地说，开展这项研究使学生(重点是代表性不足的群体)掌握多学科知识，并为与高效催化相关的学术和工业职位准备技术劳动力。与研究和专业培训相结合，孙教授致力于开展一系列教育和推广计划，与当地社区大学的学生、来自费城学区城市/高需求学校的学生和教师，以及参与坦普尔大学新获得的NSF-REU现场计划和Temple TUteach计划的学生合作。将小角X射线散射(SAXS)测量与从头计算建模和计算相结合，能够确定均匀纳米粒子的三维(3D)几何形状。该项目旨在开发一种成像协议，以便能够研究双金属纳米颗粒催化剂中3D原子分布的元素特定演化，需要两个连续的开发步骤。首先，开发了一种成像协议，通过从头算模拟多孔和中空纳米颗粒的SAXS图案，重建具有质量不连续的纳米颗粒中的三维成分分布。其次，应用质量不连续纳米粒子的成像协议，通过从头算建模和计算，从均匀的双金属催化剂纳米粒子的元素特定反常SAXS(ASAXS)图形中提取元素特定的3D图像，即ASAXS成像。ASAXS成像协议的成功开发使ASAXS成像技术的开发与原位反应堆和设备相结合，有利于研究在操作条件下正在使用的双金属催化剂中特定于元素的3D分布的时间分辨演变。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) Program and the Chemical Catalysis (CAT) Program in the Division of Chemistry, Professor Sun at Temple University is developing a real-time imaging tool to map the spatial distribution of chemical elements at atomic resolution based on x-ray scattering. He works closely with scientists at the synchrotron light sources at national laboratories to look for technical solution that could be used to provide new insights about the structure-activity relationship of catalysts during catalytic reactions. There is a significant risk to achieve the desired imaging resolution in real time and under operando conditions. However, if successful, the outcomes of Professor Sun's work could help to guide the design and synthesis of efficient catalysts, an important research area that could potentially lead to significant impacts in many industries, ranging from petroleum refineries to pharmaceutical discoveries to fuel cells. The use of the state-of-the-art large-scale facilities at national laboratories trains the students to become specialists in a significant area that is underrepresented in the typical chemist?s skill set. More broadly, performing this research educates students (with emphasis on underrepresented groups) with multidisciplinary knowledge and prepares the technical workforce for academic and industrial positions relevant to efficient catalysis. In synergy with the research and professional training, Professor Sun is committed to a range of education and outreach programs to work with local Community College students, students and teachers from urban/high need schools in the Philadelphia School District, as well as students participating in a newly awarded NSF-REU site program located at Temple University and the Temple TUteach program.The integration of small-angle X-ray scattering (SAXS) measurements with ab initio modeling and calculations results in a capability of determining three-dimensional (3D) geometry of uniform nanoparticles. This project is to develop an imaging protocol to enable the study of the element-specific evolution of 3D atom distributions in bimetallic nanoparticles catalysts, requiring two consecutive steps of development. First, an imaging protocol is developed to reconstruct 3D compositional distribution in nanoparticles with a mass discontinuity through ab initio modeling of SAXS patterns of porous and hollow nanoparticles. Second, the imaging protocol for nanoparticles with a mass discontinuity is applied to extract the element-specific 3D images from the element-specific anomalous SAXS (ASAXS) patterns of uniform bimetallic catalyst nanoparticles using ab initio modeling and calculations, so-called ASAXS imaging. Successful development of the ASAXS imaging protocol enables the development of in-situ ASAXS imaging technique by coupling with in-situ reactors and devices, benefiting the study on the time-resolved evolution of element-specific 3D distributions of metals in working bimetallic catalysts under operando conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.