With this award, the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry is supporting Dr. Yugang Sun at Temple University to combine computation and X-ray methods to develop a rapid chemical imaging tool that maps out the location of individual metals. Utilizing this tool, he and his team seek to glean a real-time, three-dimensional "picture" of metals in nanoscale metal catalyst particles on an atom-by-atom basis. Many alternative fuel sources are derived from catalytic processes based on such metal nanoparticles. New measurement methods that reveal information about the arrangement and location of metal atoms in the catalyst and how atom location and arrangement change during the chemical conversion process have great potential to enhance our fundamental understanding of catalysis in these systems. This novel solution to a long-standing challenge may well provide new insights into the how atomic-level structure affects behavior of nanometer-sized catalysts, while also holding potential to understand how the chemical behavior of other nanoparticles is influenced by their environment over time. These new measurement methods are anticipated to lead to significant impacts on chemical reactions used in industry, ranging from those that produce chemical or pharmaceutical building blocks to those that produce alternative fuels. The use of the state-of-the-art large-scale synchrotron X-ray 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, the research educates a highly diverse group of students about the use of cutting-edge chemical measurement tools to address important scientific problems, with an emphasis on workforce development in the field of alternative fuels. Dr. Sun and his team also integrate research outcomes into the Philadelphia community and beyond through a range of education and outreach programs to students and teachers at local urban/high-need schools and Community Colleges, as well as students participating in a National Science Foundation undergraduate research program and the Temple University TUteach initiative.
In this project, Dr. Sun and his research team integrate small-angle X-ray scattering (SAXS) measurements with ab initio modeling and calculation results to construct models of the three-dimensional (3D) geometry of uniform nanoparticles of well-defined chemical composition. This project is developing this imaging protocol to enable the study of the element-specific evolution of 3D atom distributions in bimetallic nanoparticle catalysts under working conditions. Such endeavors require two consecutive steps. First, the element-specific SAXS patterns are deconvoluted from the highly convoluted anomalous small-angle X-ray scattering (ASAXS) of bimetallic nanoparticles based on penalized regression methods. Second, an imaging protocol is being developed to determine element-specific 3D images of the composition distribution in bimetallic nanoparticles through ab initio modeling of the deconvoluted element-specific SAXS patterns. The ASAXS imaging protocol may then be applicable to in-situ ASAXS imaging through its use with working reactors, allowing for the study of the time-resolved evolution of element-specific 3D distributions of metals in bimetallic catalysts in operando.
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.
