Advanced Reactor Design for Ammonia Production from Electrochemical Nitrogen and Nitrate Reduction

Motivated by the increasing demand for flexible and sustainable routes of ammonia (NH₃) production, the electrochemical nitrogen (N₂) and nitrate reduction reaction (NRR and NO3RR) have attracted intense research interest in the past few years. NRR allows for distributed and on-site generation of NH₃ with water as the proton source, thereby reducing the transportation and storage costs of NH₃ and H₂. Besides N₂ which is highly abundant in the atmosphere, nitrate-N exists widely in agricultural and industrial wastewaters. NO3RR offers a promising strategy of simultaneously removing the harmful nitrate-N and generating NH₃ as a useful product from those waste streams.

While research activities on both NRR and NO3RR are blooming with substantial progress, some major challenges remain unresolved so far. Due to the wide existence of reactive N-containing species, the source of NH₃ in NRR measurements is sometimes elusive and requires rigorous examination by control experiments with costly ¹⁵N₂. On the other hand, while the electro-reduction of nitrate is much more facile, additional costs arising from the enrichment and purification of nitrate in contaminated waste resources have challenged the practical feasibility of NO3RR both technically and economically.

In this talk, we will present our latest research progress as part of the solutions to these challenges in state-of-the-art NRR and NO3RR studies, from the perspective of reactor design. An improved ¹⁵N₂ circulation system, which allows for more accurate and economized quantitative assessment of NH₃ origins, was suggested herein. For NO3RR, we developed a compact reactor system for rapid and efficient NH₃ production from real nitrate-containing waste sources, accompanied by the concurrent separation and enrichment of the produced NH₃ to yield pure ammonium compounds. Our work highlights the importance of advanced reactor design in N-related electrochemistry research, which will facilitate the transformation of the current N-centric chemical industries towards a sustainable future.