Professor Andrew A. Gewirth of the University of Illinois at Urbana-Champaign is supported by the Analytical and Surface Chemistry Program in the Division of Chemistry to examine the structure and reactivity associated with two types of electrode processes. The first involves the catalysis of nitrate reduction on bare and bimetallic electrode surfaces. The second examines the structure of solvents and other molecules on bare and monolayer-modified electrode surfaces. Information on molecules adsorbed on electrode surfaces will be obtained with a battery of spectroscopic, microscopic, and electrochemical techniques in combination with theoretical calculations. Fundamental information resulting from these studies will impact all areas of electrochemistry. Improved understanding of the structure and reactivity of electrode surfaces impacts technological processes as diverse and important as remediation, corrosion, deposition, energy storage, and catalysis. The work serves as a vehicle for interdisciplinary research training. Students from underrepresented groups will be mentored, and hands-on science and chemical demonstrations will be performed in local schools.
Electrochemical processes critically underpin technologies of broad societal impact. For example, electrochemistry is intimately associated with batteries which provide much of the portable power for modern life. Electrochemistry is also associated with electrolyzers and fuel cells which may produce and utilize hydrogen from renewable energy sources. Electrochemistry is involved with key industrial processes, such as metallization (wire connectors between transistors) in the microelectronics industry. Electrochemistry is also associated with remediation of pollutants. A key aspect of electrochemistry is the electrode surface since electrochemical events occur at or near this interface with the solution. Consequently, we are interested in understanding the electrode surface, its changes during electrochemical events, the organization of the solvent above it, and its optimization to make these events occur more easily. Under the auspices of this award, we addressed chemical transformations occurring at the electrochemically active solid-liquid interface. We developed new tools to interrogate this interface and then used these tools to study important transformations. The tools to interrogate the electrode surface involve a protocol known as ‘Shell Isolated Nanoparticle Enhanced Raman Spectroscopy’ (SHINERS), a technique which involves coating very small gold particles with especially thin layers of silica to create a substrate which enhances our ability to interrogate electrode surfaces using vibrational spectroscopy. We showed that we could address electrochemistry on hitherto hard-to-interrogate single crystal surfaces, thus showing how differences in atomic arrangements of the same element impact chemistry. In addition to work addressing the structure of water and its changes with applied potential, we also examined how small molecules organized on surfaces, and how nitrate was remediated on copper surfaces. By using the SHINERS technique, we showed that certain surface intermediates moderated and controlled nitrate reactivity on copper electrodes. This work increases the understanding necessary to design more advanced and effective materials both to remediate nitrate and to effect electrochemical transformations more generally. Work also addressed other chemistry on copper electrode surfaces. We examined the effect of certain additives on chemical-mechanical planarization, an important industrial process. We showed that benzotriazole, a common additive used in electrochemical microelectronic fabrication, formed its protective barrier in a similar manner on copper surfaces with different atomic arrangements. We also examined the mode of action of certain surfactant-based additives for copper electrodeposition. The new tools developed to interrogate electrochemical interfaces will continue to provide new insights into important electrochemical processes.
