Enhancement of NOx Production Energy Efficiency via Reaction Kinetics Optimization Utilizing Hybrid Pulse/RF Plasma

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 NOx production through hybrid pulse/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 OES results indicated that an RF electric field can effectively increase the N2 vibrational temperature. Simulation and experimental results shown that the energy efficiency of NOx 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.