Electrochemical reactive separations enable electrified nitrogen manufacturing and remediation

Abstract

Inorganic nitrogen species exhibit a wide spectrum of oxidation states and societal uses. Due to its control of oxidation states, electrochemistry is well-suited to the challenge of balancing the nitrogen cycle, which humans have drastically altered via chemical manufacturing, agriculture, and wastewater treatment. The wide variety of feedstocks that contain nitrogen species evinces a need for reactive electrochemical separations that integrate electrocatalysis to generate various species and electrochemical separations to purify them. We detail recent progress and cross-cutting insights in electrocatalysis with a focus on converting abundant reactants such as dinitrogen, ammonia, and nitrate; electrochemical separations that leverage electrochemical potential as a driving force along with various separation mechanisms (e.g., charge, volatility); and electrochemical reactive separations that leverage innovations in reactor architectures and key components. Currently, dinitrogen is reduced to ammonia, which is then oxidized to other nitrogen pathways. Electrocatalytic pathways that use reactants other than ammonia and that isolate unstable intermediates present challenging but impactful opportunities for innovation. As we consider lower-quality feedstocks that integrate environmental remediation and chemical manufacturing, selective membranes, electrodes, adsorbents, and processes will be required. For novel processes, molecular catalysts have been underutilized for treating low-grade feedstocks but can be applied in catalytic membranes or reactor architectures that extract reactants and facilitate catalysis in engineered microenvironments. Overall, opportunities abound for electrochemists and electrochemical engineers to apply their skill sets towards the critical challenge of creating circular nitrogen economies that sustain human health and environmental quality.