Influence of Water Cooling for Outer Electrode on the Discharge Characteristics of an Atmospheric Coaxial DBD Reactor

Dielectric barrier discharge (DBD) has attracted increasing attention for the applications in the gas phase plasma chemical reactions. The utilization of electrode cooling has been proved to enhance the performance of plasma chemical reactions in the coaxial DBD reactor. However, the universal understanding on how the electrode cooling improves the plasma reaction is very limited. Here, we investigated the discharge characteristics in the N2 DBD with and without water cooling for outer electrode. The influence of water cooling on the discharge characteristics of the N2 DBD was examined by the diagnostics of electrical, optical, and temperature characters. The results showed that at the same initial applied voltage, the N2 DBD with water cooling exhibited a more stable discharge with higher intensity in comparison with that without water cooling, which was reflected by the smaller decrease and higher level in applied voltage, number of current pulses, transferred charge, relative intensity of the main reactive species, and energy efficiency as a function of discharge time. From the temperature measurement, the temperature of the DBD reactor was maintained in the lower and more stable level in the presence of water cooling, indicating that more energy was injected into the plasma reactions rather than wasted as heat dissipation to the environment, which led to the higher energy efficiency in the N2 DBD with water cooling. Overall, this work provides essential references for the development and optimization of the DBD reactors in practical applications (e.g., chemical synthesis using plasma processes).