This project addresses fundamental scientific concepts encountered in synthesizing single-atom catalysts, testing their efficacy, establishing their structure-function relationships, and developing new strategies to stabilize isolated, single atoms of active noble metals. Supported noble metal catalysts play a central role in energy conversion, chemical transformations, and the improved quality of our environment. Noble metals are, however, usually very expensive. The efficient use of noble metals is a critical factor in developing and applying noble metal catalysts. The atom efficiency and specific activity (i.e., activity per atom) generally increases with decreasing particle size, with the ultimate limit of size reduction that of a single atom. Dr. Liu's approach is to anchor the single atom onto nanostructured supports to immobilize them and prevent them from clustering together. The insights gained in this investigation are being used to guide the molecular design of next-generation catalysts for energy and environmental applications. The knowledge learned in this study promotes societal broader impact in fostering chemical sustainability by reducing the usage of limited and expensive raw materials and lowering the costs of goods. Broader impacts through education are offered in an annual Winter Workshop of High Resolution Electron Microscopy, attended primarily by graduate students, and through the John C. Wheatley Education and Outreach Facility dedicated to the promotion of scientific literacy in K-12 grade students.

With this award, the Chemical Catalysis Program in the Chemistry Division and the Solid State and Materials Program in the Division of Materials Science are jointly funding Dr. Jingyue (Jimmy) Liu from Arizona State University to conduct fundamental studies of structure and reactivity of supported noble metal single-atom catalysts (SACs) and epitaxially-anchored clusters. Dr. Liu's group focuses on developing SACs with high levels of metal loading and understanding the atom-support interactions, with a goal of stabilizing single noble metal atoms (Pt1, Au1, Pd1, Ir1 and Rh1) and nanoclusters on nanostructures of Fe₃O₄/Fe₂O₃ (reducible), Al₂O₃ (non-reducible), and ZnO (difficult to reduce) supports. The proposed catalytic reactions include Pd/ZnO for steam reforming of methanol to produce hydrogen, Ir/Fe₃O₄ (Fe₂O₃) and Au/Fe₃O₄ for the water-gas-shift reaction, and Pd/Al₂O₃, Pt/Al₂O₃ and Rh/Al₂O₃ for CO oxidation. Dr. Liu's group relies on aberration-corrected electron microscopic (ACEM) techniques, especially environmental ACEM, to identify unambiguously the distribution of isolated single noble metal atoms and epitaxial nanoclusters supported on high-surface-area supports and to follow the nanocluster movement under ambient gas pressure environments at elevated temperatures. Both in situ and ex situ catalytic reaction data are analyzed in detail to understand the synthesis-structure-property relationships of supported single atom and cluster catalysts with a particular emphasis on catalytic reactions relevant to energy conversion, chemical transformations, and environmental applications. Broader impacts through education are offered in an annual Winter Workshop of High Resolution Electron Microscopy, attended primarily by graduate students, and through the John C. Wheatley Education and Outreach Facility dedication to the promotion of scientific literacy in K-12 grade students.