Enhancement of NOx production energy efficiency via reaction kinetics optimization utilizing hybrid pulse/RF plasma

Abstract Discharge plasma, grounded in non-equilibrium reaction pathways, offers the theoretical potential for fast and efficient chemical synthesis, particularly in nitrogen fixation via air plasma. However, the efficient generation of target products remains a central challenge in practical applications, due to the presence of numerous complex and unavoidable parasitic reactions within the plasma. In this study, a novel three-electrode structure was employed to control NO x production through hybrid pulse/radio frequency (RF) plasma. Through plasma emission images, it was observed that an RF electric field exceeding 500 V altered the discharge region of the pulsed discharge. The optical emission spectroscopy (OES) results indicated that an RF electric field can effectively increase the N 2 vibrational temperature. Simulation and experimental results shown that the energy efficiency of NO x production first increases and then decreases with increasing RF voltage. On one hand, a suitable RF electric field can sustain the electrons generated by pulsed discharge and provide an appropriate E/N ratio conducive to efficient NO production. On the other hand, an excessively high RF electric field may induce non-self-sustained weak ionization, leading to a loss of control over the optimized reaction pathways. This study proposes a strategy to enhance energy efficiency in plasma chemistry by selectively promoting low-threshold electron-driven reactions over ionization-dominated pathways.