Plasma-coupled electrochemical ammonia synthesis from air and water under ambient conditions

Decentralized, sustainable ammonia production could have an immense global impact. Here we describe an electrolytic approach to synthesizing ammonia directly from air and water under ambient conditions, which could be developed and optimized toward this goal. The system integrates a gliding arc discharge plasma reactor for generating ${\mathrm{NO}}_x$ from air with a membrane electrode assembly reactor for the electrochemical reduction of ${\mathrm{NO}}_x^{-}$ to ammonia, enhancing both the efficiency and scalability of the process. Furthermore, the plasma-generated ${\mathrm{NO}}_x$ feedstock can be substituted with ${\mathrm{NO}}_x$ derived from industrial waste, further extending the potential of this system. In this Protocol, we describe the fundamental principles of this plasma-electrochemical nitrogen reduction reaction (PE-N₂RR) system and provide advice for experimental standardization, operational mechanisms and data analysis methods. The procedure starts with the synthesis of the catalyst-a La_1.5Sr_0.5Ni_0.5Fe_0.5O₄ perovskite oxide-at either laboratory or industrial scale. This catalyst is sufficiently stable to enable the ${\mathrm{NO}}_x^{-}$ RR to continuously work under strongly acidic conditions. We highlight the key operating parameters that are necessary for plasma-based ${\mathrm{NO}}_x$ production and electrochemical ${\mathrm{NO}}_x^{-}$ reduction reaction systems. This information and framework can be used to optimize and streamline the entire PE-N₂RR system. A moderate level of expertise in electrochemistry, plasma systems and catalyst synthesis is recommended to ensure successful execution. The setup of the entire PE-N₂RR system, from catalyst synthesis to the configuration of plasma and electrochemical, is estimated to take 72 h. The full reaction operation test requires 200 h, whereas in situ electrochemical characterizations take 3 h.