# Chlorobenzene Removal Using DBD Coupled with CuO/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) Catalyst
## 2 Experimental Section
### Experimental Setup  
The experimental setup consisted of three parts: mixed gas generator, DBD reactor, and outlet gas detector (Figure 1). Chlorobenzene gas flow was obtained by feeding dry N\({}_{2}\) gas to a chlorobenzene bubbling bottle. The temperature of the bottle was maintained at 25 \({}^{\circ}\)C by a water bath. The chlorobenzene flow and O\({}_{2}\) gas flow were mixed in a mixing chamber before they were provided into the DBD reactor. The mass flow controllers were used to obtain the gas contained 200 ppm chlorobenzene with different gas flow rates (1-5 L-min\({}^{-1}\)). The DBD reactor (Figure 2) used in this experiment consisted of two coaxial cylinders. The inner quartz glass cylinder, filled with graphite powder with an outer diameter of 20 mm and a thickness of 1.5 mm, served as the inner electrode and ground electrode of the reactor. The outer quartz glass tube, surrounded by the copper foil with an inner diameter of 26 mm and a thickness of 1.5 mm, served as the outer electrode and the high-voltage electrode of the reactor. The copper wire with a diameter of 2 mm was used to connect the high-voltage alternating current (AC) power supply and attach the copper foil tightly to the quartz glass tube. The length of copper foil is 40 mm, creating a coaxial cylinder discharge zone 0.5 g CuO/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst (or \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) powder) was packed in the catalyst zone with an outer diameter of 26 mm, an inner diameter of 20 mm, and a height of 2 mm. The reactor was powered by an AC power with a frequency of 10-20 kHz and a voltage of 3.6-6 kV. The discharge parameters and Lissajous figure of the experiment were obtained by a 200 MHz digital phosphor oscilloscope (Tektronix, TDS2024B, Beaverton, OR, USA) using a 1000:1 high-voltage probe (Tektronix P6015A, Beaverton, OR, USA) and 0.47 uF equivalent capacitor. The specific energy density (SED; J\(\cdot\)L\({}^{-1}\)) of plasma is defined as the energy obtained per volume of gas:  
\[\text{SED}=\frac{\text{P}}{\text{Q}}\times 60 \tag{1}\]  
where P (W) is the discharge power of the DBD reactor, and Q (L min\({}^{-1}\)) is the gas flow rate. Figure 1: Schematic diagram of the experimental setup (outlet). Figure 2: Schematic diagram of the DBD reactor. In this experiment, the composition of mixed gas before and after discharge was analyzed online by a gas chromatograph (GC9790, FULI Instruments, Wenling City, Zhejiang, China) for chlorobenzene and a gas chromatograph (GC930, Haixin Instruments, Shanghai, China) for CO and CO2. The removal efficiency, CO, CO2, and COx selectivity of chlorobenzene were defined as:  
\[\eta(\%)=\frac{\left[\text{CB}\right]_{\text{in}}-\left[\text{CB}\right]_{ \text{out}}}{\left[\text{CB}\right]_{\text{in}}}\times 100\% \tag{2}\]  
\[\text{CO selectivity}(\%)=\frac{\left[\text{CO}\right]}{\left(\left[\text{CB} \right]_{\text{in}}-\left[\text{CB}\right]_{\text{out}}\right)\times 6}\times 100\% \tag{3}\]  
\[\text{CO}_{2}\text{ selectivity}(\%)=\frac{\left[\text{CO}_{2}\right]}{\left( \left[\text{CB}\right]_{\text{in}}-\left[\text{CB}\right]_{\text{out}}\right) \times 6}\times 100\% \tag{4}\]  
\[\text{CO}_{\text{x selectivity}}(\%)=\frac{\left[\text{CO}_{2}\right]+\left[ \text{CO}\right]}{\left(\left[\text{CB}\right]_{\text{in}}-\left[\text{CB} \right]_{\text{out}}\right)\times 6}\times 100\% \tag{5}\]  
where \(\left[\text{CB}\right]_{\text{in}}\) and \(\left[\text{CB}\right]_{\text{out}}\) are the inlet and outlet concentrations of chlorobenzene (ppm), and \(\left[\text{CO}\right]\) and \(\left[\text{CO}_{2}\right]\) are the outlet volumetric concentrations of CO and CO2 (ppm). The O3 concentration of outlet gas was determined by the iodometric method. The collected gas was pumped into a gas scrubber filled with potassium iodide solution with a speed of 500 mL/min for 10 min. Then 1-2 mL of dilute sulfuric acid was used to adjust the pH of absorption solution below 2.