Collaborative Research: Structure Sensitive Surface Chemistry - Small Molecule Activation and Spillover

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In this collaborative research project funded by the Chemical Structure Dynamics and Mechanisms (CSDM-A) program of the National Science Foundation’s Chemistry Division, Professors Andrew Gellman (Carnegie Mellon University) and Charles Sykes (Tufts University) are studying the influence of the atomistic structure of metal surfaces on the rates of catalytically relevant surface reactions. It is well known that the rates and selectivities of chemical reactions occurring on metal surfaces are determined by catalyst surface structure. Ideally, the design of catalysts would identify surface structures that optimize the yield of desired products. However, it is experimentally challenging to map reactivity comprehensively across the many possible structures of a metal surface. Gellman and Sykes have developed a complementary set of tools to measure surface reaction kinetics and to image atomistic surface structure across hundreds of different surface orientations concurrently. These methods will be used to generate datasets that will be used by catalyst developers to design new and improved catalytic materials. Students working on this project are gaining valuable skills in the fields of surface chemistry, x-ray spectroscopy and scanning probe microscopy.Gellman and Sykes are using spherically curved Cu and Ag single crystals that expose hundreds of different Cu(hkl) and Ag(hkl) surfaces as sample libraries for the study of surface structure and reactivity. Gellman is using spatially resolved x-ray photoemission spectroscopy to measure the rates of isothermal adsorption and activation of small molecules such as O2, CO2 and CH3CH2OH on hundreds of different Cu(hkl) and Ag(hkl) surfaces in order to identify the most active surface orientations and the trends correlating reactivity with surface structure. Sykes is studying the structures of these surfaces before and after adsorption using scanning tunneling microscopy. In addition, Gellman and Sykes are conducting similar measurements on surfaces modified by isolated atoms of metals such as Ni, Pd, and Pt to create single atom alloy catalysts with well-defined surface structures. This work will inform efforts to develop predictive theoretical models for understanding structure sensitive catalytic surface chemistry. This project also tests our current understanding of the mechanism of spillover in catalysis. Ultimately, this project is expected to advance our collective understanding of catalysis science and our ability to design new or improve catalytic materials.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.