Subsurface Hydrogen in a Alloy Hydrogenation Catalysis

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Catalysts, substances that increase reaction rates without themselves being consumed, are responsible for the production of many of the chemicals and materials on which society relies. Alloys are often more effective catalysts than the pure elements from which they are derived because their properties can be tuned by varying their elemental composition. However, this tuning poses a challenging research problem because it can require the preparation and testing of hundreds of different compositions to find the optimal catalyst. With funding from the Chemical Catalysis Program, Dr. Andrew Gellman at Carnegie Mellon University is developing and applying methods for the acceleration of such research by measuring catalytic reactions over many alloy compositions concurrently. These data are providing a comprehensive understanding of the influence of alloy composition on catalytic reaction rates and selectivities. In addition, these data are being used to develop machine learning models to predict the catalytic properties of new alloys and identify likely candidates for further testing and study. Dr. Gellman is actively involved in undergraduate research as a means of encouraging young students, especially women, to pursue advanced STEM degrees and careers.With funding from the Chemical Catalysis Program of the Division of Chemistry, Dr. Andrew Gellman of Carnegie Mellon University is integrating the use of surface analysis tools, catalytic reaction kinetics, and microkinetic modelling to study catalytic surface chemistry. His tools for concurrent measurement of catalytic reaction kinetics at 100 different alloy compositions across a Composition Spread Alloy film (CSFAF) provide comprehensive datasets to serve as the basis for understanding composition dependent trends in alloy catalysis. Dr Gellman’s work is enabling development of data rich approaches to catalysis modeling. His work allows experimental demonstration of correlations between fundamental reaction parameters such as activation barriers and catalyst characteristics such as d-band energies; correlations that previously have been accessible only through electronic structure theory. This methodology is being applied to ethylene (C2H4) and acetylene (C2H2) hydrogenation reactions. Existing work on hydrogenation reactions on Pd and Ni surfaces has suggested that subsurface hydrogen can play a role in the mechanism and influence surface reaction kinetics. Using a recently developed kinetic framework that includes subsurface hydrogen in the mechanism, Dr. Gellman is determining its role in C2H4 and C2H2 hydrogenation on Pd and Pt alloys.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.