Laser-Induced Nitrogen Fixation

Industrial ammonia production is currently performed at 400–500 °C and 100–200 bar with fossil–fuel–involved power and hydrogen feedstock by the Haber-Bosch method, which enabled the growth of humanity beyond previous limits but demands larger infrastructure, capital investments and causes substantial emissions of carbon dioxide. For distributed ammonia production and decarbonization of this process by exploiting renewable energy sources, alternative methods, such as the electrochemical approach or using plasma on a small–scale, have been explored. Nonetheless, they still lack yield and efficiency to be industrially relevant. Here, we demonstrate a new approach of nitrogen fixation to synthesize ammonia at ambient conditions via laser–induced multiphoton dissociation of lithium oxide. Lithium oxide is dissociated under non–equilibrium multiphoton absorption and high temperatures under focused infrared light, and the generated zero–valent metal spontaneously fixes nitrogen and forms a lithium nitride, which upon subsequent hydrolysis generates ammonia. The highest ammonia yield rate of 30.9 micromoles per second per square centimeter is achieved at 25 °C and 1.0 bar nitrogen. This is two orders of magnitude higher than state–of–the–art ammonia synthesis at ambient conditions. The focused infrared light here is produced by a commercial simple CO2 laser, serving as a demonstration of potentially solar pumped lasers for nitrogen fixation and other high excitation chemistry. We anticipate such solar-laser-involved technology will bring unprecedented opportunities to realize not only local ammonia production but also other new chemistry.