Fast-modulated surface-confined plasma for catalytic nitrogen fixation and energy intensification*

Nitrogen fixation is critical for plants for the biosynthesis of protein and nucleic acid. Most of our atmosphere is nitrogen, yet plants cannot directly absorb it from the air, and natural nitrogen fixation is insufficient to meet the demands. This study explored plasma-assisted nitrogen fixation using an AC-driven, surface-confined, fast-modulated pyramid electrode dielectric barrier discharge (DBD) at room temperature and pressure. The results were compared with a conventional flat electrode DBD, and it was found that the pyramid electrode plasma could excite more nitrogen molecules than the flat electrode DBD plasma, resulting in greater nitrogen fixation ability. The pyramid electrode plasma source achieved up to 50% more nitrogen fixations at lower input energy due to micro-discharges formed on the sharp edges of the electrodes. To further enhance NOX production in the plasma, metal oxide catalysts based on TiO2 were coated over the dielectric layer of the reactor. The results showed that nitrogen activation was more effective in surface-confined plasma sources because the micro-discharges formed on the sharp edges of the electrodes facilitated NOX synthesis, which was further enhanced by the metal oxide catalysts. The energy-efficient and sustainable NOX synthesis described in this study offers a new perspective for ongoing research on green nitrogen fixation techniques.