In this project, funded by the Designing Materials to Revolutionize and Engineer our Future (DMREF) Program of the Chemistry Division, Professors Graeme Henkelman and Richard Crooks at the University of Texas, Professor Anatoly Frenkel at Yeshiva University, and Professor Judith Yang of the University of Pittsburgh are combining experimental and computational methods aimed at discovering optimal bi-functional catalyst formulations and structures for the electrochemical oxidation of the poisonous gas, carbon monoxide. A key element of the research is the use of extremely small catalyst particles (containing only several hundred atoms) that are partially coated with a protective layer of molecules called dendrimers that keep the metal particles from coalescing. A variety of catalysts are being made, and their structures and catalytic activities are being analyzed. Computational studies are being performed to predict new catalyst structures that are then prepared and analyzed; the results from the experimental studies are used to refine the computational methods. The combined approach represents a new toolkit for the discovery and development of new catalytic materials having improved performance.The project participants are involved in educational and outreach activities to engage undergraduate students directly in various aspects of the project including an opportunity for some of the University of Texas - Austin students to spend up to a week at Brookhaven National Laboratory and the University of Pittsburgh.
The research team is conducting density functional theory (DFT) calculations of the entire nanoparticle structure for various combinations of metals - one which adsorbs carbon monoxide and one which adsorbs oxygen dissociatively. The DFT calculations of available reaction mechanisms, together with kinetic modeling and correlations to expected variations in catalyst structures and compositions, identify mechanisms and reactivity descriptors that will be used in subsequent screening-synthesis-characterization-evaluation cycles. Characterizations are being conducted by both in situ and scanning transmission electron microscopy (TEM/STEM) and extended X-ray absorption fine structure (EXAFS). Methods are being developed for combining the DFT calculations with the TEM and EXAFS data to improve the determination of nanoparticle structures at the atomic scale. From a scientific/technical standpoint, the study is advancing the dendrimer-aided approach to catalyst synthesis, with a clearer understanding of the nature of the particles that are produced and their catalytic activity. The study is extending previous work on bi-metallic particles to metal-metal oxide systems, with corresponding extension of computational and characterization efforts. The synthesis, characterization, and modeling tools developed during the course of this study have broad applicability to a wide range of reactions and catalyst formulations, and the software tools will be freely distributed to the catalysis science community.
