ABSTRACT

Nitrate (NO3?) is among the most ubiquitous groundwater pollutants in the world and a serious threat to human and ecosystem health. Thus, there is a compelling need to manage nitrate waste across industry, food, and water systems. The electrocatalytic nitrate reduction reaction (NO3RR) is a promising approach to convert nitrate into valuable ammonia (NH3); however, critical scientific questions and challenges surrounding NO3RR limit its practical use. The proposed research focuses on computationally addressing multiple scientific questions to better understand NO3RR to ammonia on single atom alloy catalysts. This project integrates the research with an educational outreach plan in collaboration with the Museum of Natural History at the University of Michigan and the Washtenaw Community College to promote STEM education and catalysis training.

The proposed research focuses on addressing two scientific objectives to enhance NO3RR to ammonia. Prior results showed that the maximum NO3RR activity and selectivity on transition metal electrocatalysts is hindered by linear energy scaling relations (LSRs) between adsorbates. The 1st scientific objective aims to answer mechanistic questions of NO3RR by single-atom alloy (SAAs) electrocatalysts, with the goal to break these LSRs. SAAs are a promising class of catalysts in which small amounts of isolated metal atoms are present in the surface layer of a metal host. Yet SAAs have hardly been explored for NO3RR. Using state-of-the-art Grand Canonical Density Functional Theory, we will test the hypotheses that 1) judiciously selected SAAs will break LSRs that limit NO3RR activity on pure metals, and 2) quench N-N coupling to favor NH3 selectivity. The second scientific objective aims to elucidate how geometry and electronic structure of SAAs link to NO3RR activity and selectivity. These insights will help design SAA catalysts that break LSRs for NO3RR. The expected outcomes of this research are new mechanistic understanding of SAAs and their ability to break LSRs for NO3RR, design rules for SAAs that link their properties to reactivity, and general insights into the role of solvent and applied electrochemical potential on NO3RR. The proposed educational activities are: (i) Creating a ?Research Station? museum exhibit that will teach the public about catalysis and the nitrate problem; (ii) Engaging middle school students through a summer science research program; (iii) Teaching and practicing science communication through a Science Communication Fellows Program; and (iv) Serving as summer research mentors to first-generation Community College students. The proposed integrated research and educational activities will support multidisciplinary research training, enhance STEM equity, diversity and inclusion, and increase USA economic competitiveness.

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.

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