Enhancing nitrogen-to-ammonia electrofixation via N₂ expulsion by squeezing water molecular network with kosmotropic chemistry

Electrochemical nitrogen reduction reaction (NRR) promises green ammonia synthesis under ambient conditions using water as an abundant proton source. However, the hydrogen evolution reaction (HER) is kinetically favorable and strongly competes with NRR. Additionally, the effects of local chemical microenvironment involving the electrocatalyst, N₂ reactant, and water molecular network on NRR remain unclear. Herein, we boost electrochemical NRR by functionalizing nanoelectrocatalyst surfaces with kosmotropic chemistry to manipulate water microenvironment near the catalytic sites. Systematic comparisons across five different surface chemistries show that a stronger kosmotropic character is crucial for driving NRR and supressing HER, achieving > 20-fold performance enhancement compared to chaotropic counterparts and surpassing conventional materials and surface approaches. Experimental and simulation studies corroborate the critical role of kosmotropic surface chemistry in thermodynamically trapping water molecules in a reinforced hydrogen bonding network. This phenomenon expels N₂ molecules from the water network, promoting their interactions with the electrocatalyst for enhanced NRR. Our work highlights kosmotropic surface chemistry as an efficient molecular tool for potential integration with emerging NRR electrocatalysts to jointly amplify electrochemical nitrogen-to-ammonia conversion. These insights offer enormous opportunities to chemically modulate catalytic pathways for sustainable energy and chemical applications, especially those involving water as a reactant or reaction medium.