SusChEM: Energies of Adsorbed Catalytic Intermediates on Transition Metal Surfaces

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In this project, funded by the Chemical Catalysis Program, Charles T. Campbell of the University of Washington is developing better catalysts for use in the production of bulk chemicals, fertilizers and fuels, for pollution cleanup, and for the combustion of fuels. The work involves the controlled adsorption of small groups of atoms that are often encountered in fuel cells or environmental applications to metal surfaces that are commonly used as catalysts, such as copper, nickel and platinum. When these small clusters of atoms, usually containing only carbon, hydrogen and oxygen, adsorb to a metal surface, a chemical bond is formed. The investigators are measuring the strength of these chemical bonds using a well-known technique known as calorimetry. The experimental measurements are stored in a database that is being made available to computational scientists who will perform simulations of chemical reactions that could potentially be occurring on these surfaces or in other settings. The work is, thus, having a broad impact through the creation of a publicly available resource that other scientists can take advantage of and use. It is having a further broad impact by providing the basic understanding needed to design better catalysts in order to carry out industrially important chemical reactions with higher energy efficiency and less pollution. This work is aiding the design of better batteries and fuel cells that can be integrated into solar and wind energy systems.This project is focused on calorimetric measurements of the energies of well-defined catalytic reaction intermediates (specifically -OH, -OCH3, -OOCH, -CH3 and -CH) adsorbed on single-crystal Ni, Cu and Pt surfaces. These represent five of the most common adsorbate classes evoked in catalytic reaction mechanisms, and when combined, they provide the energetics of many elementary steps that occur during energy-related and environmental catalysis. This, in turn, elucidates the energetic basis for reaction mechanisms and structure-reactivity correlations in catalysis. Campbell is collaborating with Jens Nørskov of Stanford University to combine these measurements with prior literature to create a benchmark database of reliable adsorption energies. This database will help theoreticians develop computational methods for calculating the energetics of reactions at surfaces with improved energy accuracy. While density functional theory (DFT) with periodic boundary conditions has been extremely successful in catalysis research, the method is still plagued by rather large errors in the relative energies of the adsorbed intermediates. The construction of this database is facilitating ongoing efforts in the theoretical and computational chemistry community to improve the energy accuracy of these fast computational methods. It is also aiding other researchers who seek to understand more fully the energetic basis for reaction mechanisms and structure-activity correlations in transition metal catalysis.