Nitrogen Electrocatalysis: Electrolyte Engineering Strategies to Boost Faradaic Efficiency

• Published in: ChemSusChem Vol. 16; no. 20; pp. e202300465 - n/a
• Main Authors: Thapa, Loknath, Retna Raj, C.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 20.10.2023
• Subjects: Ambient temperature; Ammonia; ammonia synthesis; Aqueous electrolytes; Aqueous solutions; Chemical reduction; Chemical synthesis; Electrochemical activation; electrochemistry; electrolyte engineering; Electrolytes; Electron transfer; Hydrogen evolution reactions; Ionic liquids; Lithium; lithium-mediated; Nitrogen; nitrogen fixation; Performance enhancement; Protons; Solubility; Water activity; Electrochemistry; Nitrogen fixation, Lithium-mediated; Electrolyte engineering; Ammonia synthesis
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300465

The electrochemical activation of dinitrogen at ambient temperature and pressure for the synthesis of ammonia has drawn increasing attention. The faradaic efficiency (FE) as well as ammonia yield in the electrochemical synthesis is far from reaching the requirement of industrial‐scale production. In aqueous electrolytes, the competing electron‐consuming hydrogen evolution reaction (HER) and poor solubility of nitrogen are the two major bottlenecks. As the electrochemical reduction of nitrogen involves proton‐coupled electron transfer reaction, rationally engineered electrolytes are required to boost FE and ammonia yield. In this Review, we comprehensively summarize various electrolyte engineering strategies to boost the FE in aqueous and non‐aqueous medium and suggest possible approaches to further improve the performance. In aqueous medium, the performance can be improved by altering the electrolyte pH, transport velocity of protons, and water activity. Other strategies involve the use of hybrid and water‐in‐salt electrolytes, ionic liquids, and non‐aqueous electrolytes. Existing aqueous electrolytes are not ideal for industrial‐scale production. Suppression of HER and enhanced nitrogen solubility have been observed with hybrid and non‐aqueous electrolytes. The engineered electrolytes are very promising though the electrochemical activation has several challenges. The outcome of lithium‐mediated nitrogen reduction reaction with engineered non‐aqueous electrolyte is highly encouraging. Engineering to break N≡N bond: N2 electrocatalysis with engineered electrolyte is reviewed. Variation of pH, diffusion of reactive species, and water activity of the electrolytes, solid‐electrolyte interface engineering, among others, boost faradaic efficiency. The Li‐mediated reduction with engineered electrolyte is promising. Challenges for industrial‐scale production of ammonia and recommendation for future studies are provided.