## 1 Introduction  
SF\({}_{6}\) gas has been widely used in gas insulated switch-gear (GIS) because of its excellent insulation and arc extinguishing performance but long-term operation experience shows that different degrees of partial discharge (PD) will occur in GIS equipment due to inherent defects or some new insulation problems [1; 2; 3; 4]. With the increase of running time, these defects develop further, which may eventually lead to serious insulation problems of GIS equipment, resulting in irreparable losses. The energy produced by the discharge causes SF\({}_{6}\) to decompose into SF\({}_{4}\), SF\({}_{3}\), SF\({}_{2}\) and other low-fluorine sulfides when the discharge continues. Some of the low-fluorine sulfides react with trace amounts of water and oxygen in GIS equipment to form SO\({}_{2}\)F\({}_{2}\), SOF\({}_{2}\), H\({}_{2}\)S and SO\({}_{2}\)[5; 6]. Many scholars have shown that by detecting the content of these characteristic decomposition products, the severity of insulation defects in GIS can be judged to a certain extent, and insulation accidents can be prevented. Therefore, the detection of SF\({}_{6}\) decomposition component content has important research significance and application value. Graphene, a typical two-dimensional carbon nanomaterial composed of sp\({}^{2}\) hybrid orbital carbon atoms, was first discovered in 2004. Due to its excellent mechanical, electrical, optical and thermal properties, it has led extensive research in many fields such as electronics, energy, biological and chemical sensors [7; 8; 9]. In 2007, graphene was first used as a sensing material and showed selectivity for typical small molecule gases [10]. Since then, its excellent sensing performance has attracted a lot of attention. The micro gas sensor made of graphene has the advantages of low operating temperature,high sensitivity and small size. In recent years, some scholars have made great progress in this field, using graphene as a sensitive material to detect H\({}_{2}\), NH\({}_{3}\), NO\({}_{2}\) and other gases. This provides a new idea for the detection of SF\({}_{6}\) decomposition products. Gas sensors based on intrinsic graphene have less response to various SF\({}_{6}\) decomposition products and poor recovery and selectivity. In order to improve the gas sensitivity of graphene, the preparation of graphene-based composites can significantly improve the gas sensitivity of SF\({}_{6}\) decomposition products, including sensitivity, response speed and recovery characteristics [11]. Nowadays, theoretical evaluation of 2D materials based on ab initial study has been widely developed. The gas sensing properties evaluated by first-principles method was an effective way to exploit high selectivity new gas sensing materials or new modified method to the surface of materials, especially for 2D graphene like materials [12; 13]. To obtain the 2D material with global minimum total energy or to get the adsorption structure with the global minimum total energy rather than the local minimum, several initial structures should be considered and several optimized structures were obtained. By comparing the final total energy or other physical properties, the final structure of materials or adsorption structure can be obtained [14; 15]. It has been proved that single-layer graphene without any defects has very week chemical interactions with most of the gas molecules [16]. To enhance the interactions between the adsorbed gas molecule and the surface of graphene, introducing transition metal or noble metal was proved to be an effective way by theoretical evaluation. Doping Fe atom or Pt atom can obviously enhance the chemical interactions between single and double layered graphene with CO, NO, SO\({}_{2}\) and HCN [17]. Especially for Pt atom or nanoclusters, they can bring many active sites on the surface of graphene as well as provide many adsorption sites for gas molecules.