# Ozone Generation by Surface Dielectric Barrier Discharge
## 1 Introduction  
As one of the strongest oxidants, ozone is widely used for sterilization, water treatment, food processing, and storage, in agriculture, textiles, and other branches of industry [1; 2; 3; 4; 5]. Of the many methods, the dielectric barrier discharge (DBD) has proven to be one of the most effective for ozone production and is commonly used at both commercial and industrial scales [6; 7]. Although the vast majority of related research has studied ozone generation in the volumetric DBD (VDBD) geometry [8; 9; 10; 11; 12], there are also some attempts to use surface DBD (SDBD) discharge for ozone production. [PERSON] et al. [13] compared the performance of small-scale VDBD and SDBD ozone generators in the planar configuration. They found that SDBD is capable of generating higher ozone density than a VDBD generator. A similar comparison was made by [PERSON] et al. [14], who studied cylindrical ozone generators. They noted that SDBD generators have the advantage of higher energy efficiency compared to VDBD generators. [PERSON] and [PERSON] [15] studied the sterilization process using a cylindrical SDBD plasma torch. They found that the nitrogen oxides generated in the discharge were the main species contributing to the sterilization process. [PERSON] et al. [16] and [PERSON] et al. [17; 18] studied the ozone flow generated by the fan-shaped SDBD reactor. They found that the fan-shaped electrode improves ozone distribution and the decontamination process compared to the traditional comb-shaped design. [PERSON] et al. [19] studied the influence of the applied voltage and its frequency on ozone production with an SDBD reactor with the radial electrode configuration. They found that ozone production generally increases with the average discharge power. [PERSON] et al. [20] studied ozone production with a planar multi-electrode SDBD reactor fed with pure oxygen. They found that they could significantly increase the ozone production yield by improving the uniformity of the feed gas in the reaction chamber. [PERSON] al. [21] studied the influence of the feed gas (oxygen) concentration and humidity on ozone production using a symmetric SDBD reactor. They found the optimal gas feed rate to maximize the ozone production yield. They also confirmed the negative influence of humidity on ozone production. However, in recent years, SDBD has been finding more and more applications outside ozone generation, such as thrust generation [22; 23; 24; 25; 26; 27], EHD (electrohydrodynamic) airflow generation [28; 29; 30] and flow modification [31; 32; 33], as well as air and water purification [34; 35; 36; 37; 38]. Yet, the toxicity of the ozone generated by the SDBD discharge may be an obstacle to the implementation of SDBD in some applications, especially if the discharge is to work in an enclosed room where people are present [39]. To the best of our knowledge, so far, only [PERSON] et al. [40] have studied the process of ozone generation as a potential obstacle to controlling the detachment of the boundary layer from the surface of vehicles using SDBD actuators. They concluded that even though the amount of ozone generated in the SDBD discharge is lower than in the case of VDBD, in order to introduce this technology to the automotive industry, the amount of generated ozone would still have to be significantly reduced. The aim of this work was to determine whether SDBD generators (in the form of flow actuators, ionizers and precipitators) can be safely used in close proximity to people (especially indoors). In this paper, we experimentally studied the performance of the three types of SDBD generators (varying in the geometry of the high-voltage electrode) in terms of the amount of ozone they produce. We extensively studied the electrical characteristics of the discharge by measuring the discharge current and the dissipated power. We used a time-resolved imaging technique to investigate the morphology of the discharge plasma.