Professors Richard M. Crooks and Graeme Henkelman of the University of Texas at Austin are supported by the Chemical Catalysis Program of the Division of Chemistry to undertake fundamental studies of catalytic materials. The project is aimed at developing a better understanding of nanometer-scale electrocatalysts. The historical approach for developing new catalysts is based on the Edisonian method of using scientific intuition followed by trial-and error-testing. With the advent of very powerful computers, however, it has become possible to imagine designing catalysts using sophisticated calculations. Accordingly, the main scientific goal of the present research project is to experimentally test the validity of this approach to catalyst design. To accomplish this goal, individual, well-defined nanoparticles are first synthesized, structurally characterized and their electrocatalytic properties evaluated. This initiates an experimental-theoretical iterative relationship intended to refine theoretical tools to the point that they will eventually be sufficiently sophisticated to be used to design more effective electrocatalysts from first principles. Electrocatalysts are important for converting chemical fuels, like hydrogen, into energy, and also for the opposite family of reactions in which energy is converted to and stored in the form of fuels. With rising concerns over the security and sustainability of the nation's energy future, and the scarcity of several key catalytic materials, it is more important than ever to efficiently design more accessible and effective electrocatalysts. During the course of conducting this research, students are provided with the technical knowledge necessary to contribute toward a clean-energy future and the communication skills necessary to convey the importance of energy-related science to citizens and the nation's political leadership.
The central objective of this project is to synthesize, characterize, and evaluate the electrocatalytic performance of individual nanoparticles (NPs), and then correlate their properties to those calculated using first-principles theory. To address this objective, three specific aims are identified. Specific aim 1 commences with the discovery of methods for controlling the electrosynthesis of single platinum NPs (PtNPs) onto the tips of individual, nanometer-scale carbon electrodes. Detailed surface structural characterization of these materials is determined using electron microscopy, nanobeam diffraction, and scanning tunneling microscopy. This structural information is used to predict, using first-principles theory, the electrocatalytic efficiency of these materials for carbon monoxide (CO) and formic acid oxidation. CO oxidation is selected for study because it is one of the simplest electrochemical reactions reported in literature in which clear effects of NP structure on electrocatalytic activities have been observed. It also often forms as an intermediate or by-product in electrocatalytic oxidation reactions of organic fuels. The theoretical approach involves defining particular descriptors for these reactions. Initially, these descriptors will be determined by postulating reaction mechanisms and then calculating binding energies of reaction intermediates. The resulting theoretical predictions are then experimentally tested. Specific aim 2 advances the foregoing methodology by expanding the library of achievable surface structures, which in turn provides a more rigorous test of theory. Finally, in specific aim 3, the scope of the project expands further to include other single-NP systems, including gold NPs and single-atom alloyed NPs. In this part of the project, theory guides the choice of electrocatalytic reactions and the combinations of materials tested. The goal of this aim is to demonstrate the scope of the methodology and to further challenge the predictive reliability of theory.
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.
