Title: Electrochemical Conversion of Carbon Dioxide and Nitrogen to High-Value Products Using Engineered Metal-Ligand Interfaces
Plants do a wonderful job of converting gases like carbon dioxide and nitrogen into products like cellulose and nutrients. The reactions are driven by sunlight and provide a critical balance to life - including oxygen in the atmosphere and our food supply. In the last century, man is responsible for significant changes in the balance; atmospheric carbon dioxide levels have risen by about 30% and more than 50% of the world population now relies on man-made fertilizers for food. Unfortunately, there are no commercial processes that can duplicate the ability of nature to use sunlight, atmospheric gases and water to make fuels, plastics or fertilizers. However, this remains a grand challenge for science and technology and efforts to achieve some measure of success still require funding. This GOALI award is made to a team comprised of Professors John Flake and Ye Xu and Dr. Joe Sauer of Louisiana State University and A&M College and Dr. Anne Sauer of Albemarle Corporation. The aim of this work is to mimic nature and design new catalysts that can produce valuable products from these basic feedstocks. Catalyst surfaces and interfaces will be created using highly active metal clusters and functional ligand molecules that promote the selective formation of one particular product over another. The energy to power the reaction is ideally provided solely by electricity from solar or wind energy (no fossil fuels). The research will shed light on the fundamental behavior of electrocatalysts and the team of academic and industry investigators will work to commercialize "green" processes to make chemicals, fertilizers and fuels using purely renewable resources.
The overarching goals of this project are to: (1) build a fundamental framework for understanding the behavior of ligand-functionalized metal nanoclusters as electrocatalysts and (2) leverage this understanding to create electrocatalysts by design. The team will explore the roles of metal type, nanocluster size, ligand chemistry and their behavior in electrolytic reactions using a combined theoretical and experimental approach. While there has been a renewed interest in electrochemical CO2 reduction in recent years (including for solar fuels), the reaction pathways and selectivity-controlling mechanisms are not well understood. Likewise, the mechanisms involved in N2 reduction are also poorly understood. The investigators will explore reduction pathways as a function of nanocluster size/type (Au, Ag, Cu, Ni, Fe) and ligand chemistry (e.g. thiols, sulfides, amides, amines, imines and other sulfo- or amino-functional groups) using voltammetry, surface analyses and other product characterization tools. The work will include a special in-operando spectroscopic study of electrocatalytic reactions using synchrotron-source XANES (X-ray Absorption Near Edge Spectroscopy) analysis to probe reactions as they occur. These experimental results will be complemented by density functional theory (DFT) based modeling techniques to generate an in-depth understanding of the nature of the active electrode interface, the key steps in the electrochemical reduction of CO2 and N2, and the cooperative effects between the electrode and the ligand. The versatility and accuracy of modern DFT methods will be leveraged to identify the fundamental factors that systematically control the efficiency and selectivity of the reactions, and subsequently to predict the performance of new electrode/ligand combinations. Results from this work will yield new insights into reactions mechanisms, a framework for predicting and controlling selectivity, and new electrocatalysts to produce fuels, fertilizers, and chemicals.
