Plasma-catalytic Purification of NO over N-TiO2 in a Dielectric Barrier Discharge Reactor

Abstract

In order to improve the purification efficiency of a vehicle-mounted purification reactor, photocatalysis and plasma technology were combined to study the purification effect of NO (nitric oxide) emitted by the two technologies through the dielectric barrier discharge (DBD) plasma system. Based on the single factor variable method, the relationship between the effect of purifying NO and the influencing factors (input energy, humidity, gas flow, ozone) was obtained. The test results show that under the better conditions (input voltage was 20KV and frequency was 200Hz, humidity was 5000ppm, gas flow was 100mL/min), under the synergistic effect of plasma and N-TiO₂ (concentration of nitrogen in N-TiO₂ was 5 at.%), NO purification is the best, with an efficiency of around 94.25%. Because of  the action of the DBD electric field, more narrowed band gaps (such as 3.08 eV) are more likely to produce active species (•OH and O₂•?) that form on the N-TiO₂ surface. Changes will significantly affect the effect of NO purification. For example, With the increase of input power, NO removal efficiency also increases greatly,and a certain humidity causes the synergistic effect of purifying NO to increase first and then decrease. This is mainly because the free electrons and active substances under the action of the DBD electric field increase with the increase of external input energy. More water molecules easily form negative ions with free electrons, thereby reducing the number of free electrons in the discharge space. In addition, in a certain flow rate range, due to the decrease in the chance of contact between the contaminant and the active material, When the flow rate increases gradually, the purification rate of the contaminant will gradually decrease. The outgrowth of the DBD electric field, ozone, always plays a role as a promoter in the purification of NO.