The electrochemical nitrogen reduction reaction (eNRR) offers an attractive, sustainable alternative to the energy-intensive Haber–Bosch process for ammonia synthesis. While catalyst design remains crucial, recent reports have highlighted the critical role of electrolyte physicochemical properties in boosting performance. Key factors include N2 solubility, the fraction of available free water, and pH. This work unveils a powerful strategy to enhance performance by rationally tuning the electrolyte environment using water-in-salt electrolytes (WISEs). The physicochemical properties of different salts and concentrations were systematically investigated: LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) at 12 m and 15 m (m = mol kg–1), alongside ultra-high-concentration CH3COOK (potassium acetate) at 28 m. Our comprehensive experimental results, corroborated by theoretical calculations, demonstrate that both the nature and concentration of the electrolyte directly govern solubility and the availability of water in the system, which consequently influences the pH. To validate these findings, a catalyst already described for eNRR, silver nanoparticles (Ag NPs) encapsulated by a zeolitic imidazolate framework (ZIF-8), giving Ag@ZIF-8, was synthesized, characterized, and tested across different WISEs for the eNRR. The best performance was achieved under the ultra-high salt concentration of 28 m CH3COOK. This optimized environment resulted in a Faradaic efficiency (FE) of 46.4% at 0.0 vs RHE and an ammonia yield rate of 2993.53 μg mgAg–1 h–1. The results obtained are consistent with the predicted tailored physicochemical properties of the WISEs. This study offers an alternative strategy to enhance ammonia electrosynthesis by tuning electrolytic conditions, demonstrating its relevance in advancing sustainable nitrogen fixation technologies.
Ferrer et al. (Tue,) studied this question.