Sustainable NOx production from air in pulsed plasma: elucidating the chemistry behind the low energy consumption

Abstract

N-Based fertilisers are paramount to support our still-growing world population. Current industrial N₂ fixation is heavily fossil fuel-dependent, therefore, a lot of work is put into the development of fossil-free pathways. Plasma technology offers a fossil-free and flexible method for N₂ fixation that is compatible with renewable energy sources. We present here a pulsed plasma jet for direct NO_x production from air. The pulsed power allows for a record-low energy consumption (EC) of 0.42 MJ (mol N)⁻¹. This is the lowest reported EC in plasma-based N₂ fixation at atmospheric pressure thus far. We compare our experimental data with plasma chemistry modelling, and obtain very good agreement. Hence, we can use our model to explain the underlying mechanisms responsible for this low EC. The pulsed power and the corresponding pulsed gas temperature are the reason for the very low EC: they provide a strong vibrational–translational non-equilibrium and promote the non-thermal Zeldovich mechanism. This insight is important for the development of the next generation of plasma sources for energy-efficient NO_x production.