# Pentane Depletion by a Surface DBD and Catalysis Processing
## 2 Experimental Setup  
The configuration adopted in our experiments, the simplest version of the SDBD used in plasma aerodynamics applications, is called a plasma actuator. It consists of two conducting electrodes attached to the opposite sides of a flat dielectric panel, as seen in the asymmetrical arrangement sketched in Figure 1.  
The lower electrode is covered with an insulating material, whereas the upper one remains fully exposed to the air. In this way, the plasma generation region is confined above the dielectric plate. For the dielectric barrier, we used a vetronite sheet, with the possibility to change its thickness (1.5-3.0 mm). More specifically, we used a 1.5 mm thick dielectric barrier in vetronite and a pair of 12 cm long conductive electrodes leaning on the two faces of the barrier. Upon the application of a sufficiently high voltage (HV), the air portion in proximity to the device gets weakly ionized, thus creating a thin plasma layer above the insulating plate, as illustrated in Figure 1. The SDBD plasma actuator generates a non-thermal self-limiting plasma, in which the accumulation of charged particles on the dielectric surface opposes the applied electric field. Consequently, AC or pulsed high voltages are required to have a temporally prolonged discharge operation; otherwise, only a transient air ionization occurs at the voltage ignition. In the present configuration, the exposed electrode is grounded, whereas the covered one is fed by a high-voltage power supply line. This consists of a DC-voltage supplier and  
Figure 1: Plasma device scheme: The two electrodes, consisting of deposed copper (35 μm thick, 4 μm wide, and 12 cm long), are attached to a dielectric material and are laterally shifted from each other by about 0.5 cm (typical asymmetry in SDBD). The lower electrode, fed at a high voltage (HV), is covered with an insulating material, whereas the upper one, fed to the ground, is exposed to air. The HV probe measures the applied potential. a signal generator feeding the primary windings of an HV transformer, whose secondary windings are connected to the electrode. We set the reference DC supply voltage (VDC) within the range of 7-14 V. The whole system behaves similarly to a resonant circuit, so the sinusoidal voltage frequency slightly depends on the DC-supply voltage. In this asymmetric configuration, due to the partial overlapping of the electrodes by about a centimeter, a so-called ionic wind is generated, which is a directional flow from the exposed electrode to the buried one. The SDBD is located in the reactor, a parallelepiped with the size of 1.8 \(\times\) 20 \(\times\) 18 cm\({}^{3}\) made by Delrin and with a cover in Plexiglas (box used for the experiments that has not been attacked by the used VOC or its decomposition products), inside which VOC depletion takes place. The volume of the free space used for the air treatment is about 0.5 L. The experiments were performed in static conditions, as described below. The VOC used in this experiment is pentane (C\({}_{5}\)H\({}_{12}\)), employed at variable concentrations between 300 ppm and 1200 ppm. The VOC contamination setup is shown in Figure 2. The black bold lines represent the tube connections through the whole system. In the diagram, \"Pure air\" represents a gas cylinder from Sapio S.R.L. containing 79% N\({}_{2}\) and 21% O\({}_{2}\), which means that the concentration of CO\({}_{2}\) (0.5 ppm), CO (0.5 ppm), hydrocarbons (0.1 ppm), water (3 ppm), and other pollutants is negligible. The red crosses represent ball valves. The liquid pentane is placed in a bubbler bottle (denoted as Liquid VOC in Figure 2) and is allowed to circulate through the flow meter by the action of the air pressure. We used two gas flow meters and one liquid flow meter, all produced by the Bronkhorst factory. The controlled evaporator and mixer (CEM) allow the liquid coming from the liquid flow meter to evaporate and mix with a line of pure air that comes from gas flow meter 1, thus producing the first dilution of pentane.