Innovations at the Nexus of Food, Energy, and Water Systems: Electrochemical Approaches to Sustainable Dinitrogen Fixation

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In this project funded by the Chemical Catalysis Program of the Chemistry Division, scientists from the University of North Carolina at Chapel Hill (UNC), Yale University, and Rutgers University are collaborating to develop approaches to sustainable electrochemical fixation of nitrogen (N2). Sustainable nitrogen fixation is central to the nexus of challenges in food, energy, and water chemistry. Current global food production is enabled by the use of synthetic fertilizer that is produced by nitrogen fixation processes that generate ammonia (NH3) from nitrogen and hydrogen (H2), but leave a dramatic negative impact on energy and the environment, consuming about 2% of the world's fossil fuel-derived energy supply. In this project, Prof. Alexander Miller (UNC), Profs. James Mayer and Patrick Holland (Yale), and Profs. Alan Goldman and Gal Hochman (Rutgers) are exploring new, sustainable methods for nitrogen fixation. New chemistry will be developed that could enable the development of electrochemical nitrogen fixation processes that do not require consumption of fossil fuels to produce ammonia and nitrates. Sustainability and policy analysis will assess the potential for transformative impact on global agriculture and energy sectors (including consideration of ammonia as a possible liquid transportation fuel). The project will train graduate students and postdoctoral researchers in interdisciplinary problem-based scientific methods and positively impact institutional infrastructure. The topic and the results of the research will be used as a platform to teach non-scientists about the importance of chemical catalysis in industry, agriculture, and modern society in general. The interdisciplinary research team has strengths in catalyst design and synthesis, electrocatalysis, mechanistic studies, and sustainability and policy analysis. The chemical approach to N2 fixation involves transition-metal-electrocatalyzed reductive splitting of N2 into nitrido intermediates. These nitrido intermediates can undergo (a) nitride reduction to NH3 by proton-coupled electron transfer (PCET), or (b) nitride oxidation toward nitric acid. Middle-to-late transition metal complexes of robust and tunable pincer ligands will be an experimental focus, with complementary computational studies to correlate reactivity with molecular properties and guide catalyst development. The cost of potential electrochemical N2 fixation processes will be analyzed, to estimate the dependence on a range of factors such as diversity of electricity sources, intermittency of sustainable energy, and governmental policy.