Electrochemical Ammonia Synthesis from Different Nitrogen Sources with Validated Analysis

Ammonia is a vital chemical feedstock for agriculture and a promising energy carrier. However, its conventional synthesis via the Haber Bosch process is energy and carbon-intensive, thus the need for sustainable alternatives. Yet, emerging electrochemical approaches to ammonia synthesis often suffer from low yields, competing side reactions such as hydrogen evolution, a high activation barrier, and complex multi-electron/proton pathways. Therefore, active, efficient, and selective electrocatalysts coupled with rigorous analytical methods are needed to overcome these challenges. In this thesis, I address these challenges by rational catalyst design and improved ammonia detection methods to achieve efficient green ammonia production. First ammonia synthesis from diverse nitrogen sources (N2, NO3−, NO2−, and NO) under ambient conditions was reviewed, highlighting recent catalyst advancements, catalyst designs, and system-level developments in detection methods, electrolytes, and reactor designs. The N2 reduction pathway were compared with nitrate, nitrite, and NO reduction pathways for sustainable NH3 production. Next, I develop a proton nuclear magnetic resonance method for ammonia quantification with minimal sample preparation, achieving a low detection limit of 1.5 µg L−1 in both aqueous and non-aqueous systems. This method is used to detect the ammonia produced by our catalyst design. A single-atom Au(III) catalyst for electrochemical N2 reduction in acidic aqueous media was developed, achieving over 50% faradaic efficiency. Control experiments confirm that the high Au3+ oxidation state suppresses the competing hydrogen evolution reaction, thereby enhancing ammonia production. To overcome the limitations of isolated single-atom catalysts, I report the development of a dual-atom catalyst with neighbouring Cu and Co sites that synergistically activate N≡N bonds while inhibiting proton reduction, achieving a high faradaic efficiency of 87%. Finally, given the persistent limitations of direct N2 reduction, consider nitrate as an alternative nitrogen source. I developed a Cu4Fe alloy on a porous Cu electrode that enables nitrate reduction to NH3 with 99.1% faradaic efficiency at a high current density of 3.83 A cm−2, achieving gram-scale NH3 production. Finally, these studies provide insights into catalyst design and ammonia detection strategies, opening the path for efficient and scalable green ammonia production as a sustainable alternative to Haber–Bosch.