CAREER: Understanding Bifunctionality in Organic Electro-oxidation Catalysis

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Renewable electrical energy from sources such as wind farms, photovolataic devices, and hydroelectric power can be used to carry out a wide range of chemical reactions important for fuel cells, wastewater treatment, sensors, and chemical manufacturing. Currently, the energy for those reactions is derived primarily from fossil fuels, but renewable electricity offers opportunities to secure our nation's energy future while dramatically decreasing environmental impacts. The project will develop and apply new analytical tools to understand the molecular-level processes needed to make electrochemical reactions efficient. Focus will be placed on understanding ways to use electricity and the oxygen in water to directly convert methanol into commodity chemicals such as formic acid and formaldehyde. The same tools can be applied to the design of methanol fuel cells for energy generation. Insights from the methanol studies will provide a framework for applying electrochemical catalysis to a wide range of organic molecules. The research will be integrated with educational and outreach activities, including an "Energy Academy" program with a regional high-school. Organic electro-oxidation reactions are critical to applications in wastewater treatment, sensing, distributed-scale chemical synthesis, and a multitude of direct-organic fuel cells. Many of these technologies can be built around an interconnected network of single-carbon molecule chemistries involving oxidation of methanol, formaldehyde, formic acid and carbon monoxide. A role for "bifunctional" catalysis - in which one catalyst component selectively activates the organic and the other selectively activates water to form reactive oxygen species - has been widely promoted in the electro-oxidation literature, as well as other areas of catalysis. This project seeks to classify and rationalize the operative mechanisms (bifunctional or otherwise) of two-component electro-oxidation catalysts, and to demonstrate design principles for controlling partial or total oxidation of small organic molecules. An analytical platform, recently developed by the principal investigator, will be used to perform kinetic measurements on well-defined bimetallic nanostructures during rapid bulk electrolysis in flow. The system also forms the basis for the first true liquid electrochemical implementation of steady-state isotope-transient kinetic analysis, permitting direct measurement of product-specific active-site coverages (observed via surface isotope exchange during an otherwise-steady-state reaction) using online electrochemical mass spectrometry. Further insight will be leveraged from top-atomic layer surface analysis by low-energy ion scattering and other auxiliary characterization methods including in-situ infrared spectroscopy and electron microscopy of materials in order to understand the mechanistic pathways governing bifunctional oxidation, and use that knowledge to design new catalytic materials. Critical questions to be answered relate to the determination of the nature of the active sites (e.g. whether carbon-oxygen coupling steps happen at interfaces as opposed to spillover phenomena), their distribution, and their resulting interactions (e.g. how altering one functional component may inadvertently influence the other), with the ultimate goal to rationally control the activity, selectivity, and stability of the electrocatalysts.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.