Catalyst-Free Activation and Fixation of Nitrogen by Laser-Induced Conversion

Ultrafast N₂ fixation reactions are quite challenging. Currently used methods for N₂ fixation are limited, and strong dinitrogen bonds usually need to be activated via extreme temperature or pressure or by the use of an energy-consuming process with sophisticated catalysts. Herein, we report a novel laser-based chemical method for N₂ fixation under ambient conditions without catalysts, this method is called laser bubbling in liquids (LBL), and it directly activates N₂ in water (H₂O) and efficiently converts N₂ into valuable NH₃ (max: 4.2 mmol h^-1) and NO₃^- (0.17 mmol h^-1). Remarkably, the highest yields of NH₃ and NO₃^- are 4 orders of magnitude greater than the best values for electrocatalysis reported to date. Notably, we further validate the experimental mechanism by using optical emission spectroscopy to detect the production of intermediate plasma and by employing isotope tracing. We also establish that an extremely high-temperature environment far from thermodynamic equilibrium inside a laser-induced bubble and the kinetic process of rapid quenching of bubbles is crucial for N₂ activation and fixation to generate NH₃ and NO via LBL. Based on these results, it is shown that LBL is a simple, safe, efficient, green, and sustainable technology that enables the rapid conversion of the renewable feedstocks H₂O and N₂ to NH₃ and NO₃^-, facilitating new prospects for chemical N₂ fixation.