Collaborative Proposal: NSF-DFG Echem: Understanding the Mechanism of Urea Oxidation on Nickel-Based Electrocatalysts

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Urea – a common high-nitrogen chemical waste product of mammalian metabolism, and a major component of fertilizer – poses significant threat to water resources from agricultural run-off and municipal wastewater. A promising means for removing excess urea is to oxidize it electrochemically to produce produce harmless compounds. Urea removal processes can also be used to generate electricity and to produce hydrogen for fuel cells. Electrochemical urea removal therefore exhibits strong potential as a transformative technology by converting a harmful waste product to the benefit of society, industry, and the environment. The project brings together researchers from the United States and Germany to apply a synergistic blend of experimental and theoretical methods to the study of electrochemical urea removal from water. In particular, the project seeks fundamental understanding of catalytic urea oxidation that is needed to develop feasible urea removal technologies. Effective urea removal systems are key to a large number of technological applications including municipal and agricultural wastewater treatment, remediation of fertilizer run-off, ammonia synthesis, hydrogen production, and electricity generation. Other benefits from this project will include workforce development and educational outreach to underrepresented grade-school students. These efforts will promote increased diversity in STEM fields, a student exchange program between Germany and the US, and improved scientific literacy of the general public.The goal of this research project is to develop comprehensive knowledge of electrochemical urea removal over nickel-based catalysts, based on experimental and theoretical research spanning molecular and device levels. Electrochemical urea removal will be studied by density functional theory calculations, vibrationally and electronically resonant sum frequency spectroscopy, and electrochemical measurements of reaction rate and product distributions. Particular attention will be paid to the active form of the nickel oxide electrode as it exists in different phases and oxidation states depending on electrode potential and history, such as aging and preparation method. This combined electrochemical, spectroscopic, and computational approach provides insight related to catalyst structural changes and how they affect the urea reaction mechanism, reactivity, and effectiveness of nickel, nickel-iron, and nickel-chromium catalysts. The outcomes of this research will greatly advance the scientific understanding of electrochemical urea removal -- about which little is known -- and establish a foundation in the wider field of electrocatalysis regarding electrochemical reactions on oxide surfaces and on surfaces that undergo a change in oxidation state as part of the overall reaction mechanism. Successful completion of this research will benefit society through sustainable methods for treating wastewater and agricultural run-off that will reduce demand on water supply systems and enhance the biodiversity of marine ecosystems.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.