## 1 Introduction  
NO\({}_{\mathrm{x}}\), one of the primary air pollutants, can cause various effects such as photochemical smog, secondary aerosols, and tropospheric ozone [1; 2; 3; 4; 5], although NOx plays a positive role in biology [6]. Therefore, abatement of NOx is a subject of great concern around the world. Nonthermal plasma (NTP) can destroy NOx in the gas stream with relatively low energy consumption, ease of operation, and compact system. Dielectric barrier discharge (DBD), one of the most promising NTP generation technologies at an atmospheric pressure with highly efficient and eco-friendly advantages, has even paid attention by 'plasma medicine' [7] and particularly distinguished performance in the decomposition of NOx via conventional methods [8; 9; 10].  
Given that NO is the main component of NO\({}_{\text{x}}\) in exhaust gas, the removal of NO is the core problem involved in the denitration field [11; 12; 13]. Recently, substantial research work using DBD reactors were developed for NO abatement [14; 15; 16; 17; 18; 19]. Moreover, in most studies, high electron energy was considered the key factor in controlling plasma processes for NO removal [20; 21]. Therefore, many researchers have paid attention to the investigation of improving the electron energy of DBD reactors to achieve higher destruction and removal efficiency (DRE) of NO [22; 23]. However, high electron energy can lead to the production of new NO\({}_{\text{x}}\) by the oxidation of N generated from N\({}_{2}\) dissociation in the DBD reactor. Therefore, preventing new NO\({}_{\text{x}}\) production and improving the better by-product selectivity gradually becomes a great concern on the NO abatement by DBD technique [24; 25]. Many researchers investigated the role of electron energy in NO abatement and studied several influencing factors such as input power, electrode gaps and dielectric relative permittivity [26; 27; 28; 29; 30]. Nevertheless, limited attention has been given to the relation between electron energy and electrode structure although the latter is considered as one of the most important factors in controlling electron energy [41; 42].  
Numerical simulation, an effective tool in developing the NTP theories and determining the operating parameters, has been developed in recent years [43; 44]. Numerical study of the DBD operation is conventionally focused on plasma modeling approaches, namely, fluid and kinetic plasma description. Particle-in-cell with Monte Carlo collisions (PIC-MCC), a new plasma modeling approach, has been verified to predict different types of discharge and to describe the breakdown stage of discharge or plasma decay stage [45]. These modeling results can provide important information about the qualitative description of the electron energy and the force generation by DBD plasma [46]. These results have illustrated the distribution of electron energy and active particles in the atmospheric air. However, electron energy and its distribution in DBD reactors with different electrode structures for NO abatement were not discussed.  
This study aims to investigate the effect of electron energy and electrode structure on the abatement of NO\({}_{\text{x}}\) and preferable by-product selectivity in two different DBD reactors. Reaction products and chemical reaction mechanism of NO abatement were performed by Fourier transform infrared (FTIR) to provide further analysis information on NO destruction and new NO\({}_{\text{x}}\) production. Then, electron energy, electron energy distribution and partial discharge of two different plasma reactors were investigated in a NO-N\({}_{2}\)-O\({}_{2}\) system using PIC-MCC simulation method. The electrical signals in DBD reactors were also analyzed to explore the discharge effect of electrode structures. Based on experimental and numerical research, the mechanism involved and preferable means of controlling the new NO\({}_{\text{x}}\) production in DBD reactor are also suggested. The results can provide useful information on DBD application for NO abatement.