Insights into plasma-catalytic nitrogen fixation from catalyst microanalysis and chemical kinetics modelling

Current industrial nitrogen fixation technology is unsustainable and has adverse environmental effects due to its reliance on fossil fuels. Using electricity-driven non-thermal plasma catalysis to fix nitrogen into NO3− is a promising solution, but the underlying mechanisms remain largely unknown. This study integrates a structured catalyst into a plasma column with a water-electrode bubble reactor that can fix nitrogen at ambient pressure and temperature with a 93% selectivity to NO3− with excellent catalytic stability. Characterizations of the catalyst and in situ plasma diagnostics indicate that the enhanced production of nitrate ions is due to abundant chemisorbed oxidized nitrogens species originating from NO and NO2 produced by the air plasma. The plasma chemistry model combined with DFT simulations demonstrates the role of structured TiO2 supported by 5% graphene oxide (GO) to improve NOx surface association while minimizing NOx backwards dissociation. The modelling results suggest the critical role of NO3(ad) in enhancing NOx production predominantly in the form of N2O5 molecule in the gas phase, resulting in efficient NO3−(aq) production as a final product in water. The study offers novel findings on plasma-catalyzed nitrogen fixation, advancing its potential for clean energy and eco-friendly chemical production through plasma-based power-to-chemical processes.