Mechanochemical ammonia synthesis enhanced by silicon nitride as a defect-inducing physical promoter

By enabling ammonia synthesis under near ambient conditions, mechanochemistry provides a paradigm shift, a new decentralized production method that avoids the high temperature (above 400 °C) and high pressure (above 200 bar) requirements of the centralized Haber-Bosch process. Leveraging the principles of mechanochemistry and its dynamic reaction environment, we hypothesize that inducing high-density defects on iron (Fe) catalyst can amplify catalytic activity by increasing initial state and adsorption capacity. In this study, we introduce a novel mechanochemical ammonia synthesis method utilizing silicon nitride (Si3N4) as a defect-inducing physical promoter. The physical properties of Si3N4 make it an ideal candidate to more efficiently generate active surfaces on Fe catalyst via mechanochemical actions. The Fe catalyst with Si3N4 (3.0 at%) promoter achieves an ammonia concentration 5.6-fold higher than unpromoted Fe, while maintaining substantial stability. This research not only establishes a promising pathway for low-energy ammonia production but also provides insights into dynamic defect engineering strategies for catalytic systems.