Challenges and Advancements in Sustainable Ammonia Production via Electrochemical Nitrogen and Nitrate Reduction

Ammonia (NH3) is a cornerstone of modern society, serving as the basis for all nitrogen fertilizers, which sustain nearly half of the world’s population. Furthermore, thanks to its high energy density (4.32 kWh L⁻¹ for liquid NH3) and ease of liquefaction, ammonia is emerging as a potential renewable energy carrier and fuel for decarbonization efforts. However, current NH3 production relies heavily on the Haber-Bosch process (HBP), which is highly energy-intensive, consuming 1–2% of global fossil fuels and accounting for approximately 2% of worldwide CO2 emissions. This underscores the urgent need for sustainable and decentralized NH3 synthesis technologies. Electrochemical nitrogen and nitrate reduction reactions (E-NRR and E-NO3RR) have garnered significant attention as greener alternatives to the HBP. These processes allow for renewable electricity utilization and on-site, on-demand ammonia production. Additionally, nitrate (NO3⁻), a widespread pollutant in groundwater due to its high solubility, can be converted into valuable NH3 via E-NO3RR. However, both E-NRR and E-NO3RR face challenges and low production rates, insufficient Faradaic efficiencies and high overpotentials represent an intriguing challenge. The main components contributing to the overall system performance are the catalyst, the electrolyte and the reactor and thus their full comprehension is crucial to boost E-NRR and E-NO3RR technologies. Despite advancements, reproducibility issues and scaling challenges persist. In conclusion, E-NRR and E-NO3RR offer promising pathways for sustainable ammonia production, with significant potential for scalability and integration with renewable energy. Continued research into advanced catalysts and electrolyte formulations is essential to overcoming current limitations and achieving the full potential of these technologies.