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

Ultrafast N-2 fixation reactions are quite challenging. Currently used methods for N-2 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 N-2 fixation under ambient conditions without catalysts, this method is called laser bubbling in liquids (LBL), and it directly activates N-2 in water (H2O) and efficiently converts N-2 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 N-2 activation and fixation to generate NH3 and NOx 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 N-2 to NH3 and NO3-, facilitating new prospects for chemical N-2 fixation.