## 1 Introduction  
The research on carbon-doped materials has received more and more attention from academia. Especially, the interaction between conductive polymers, such as polyaniline (PANI) and carbon nanomaterials, such as multi-walled carbon nanotubes (MWCNTs) and carbon quantum dots (CQDs), has been researched hotspots since its discovery [1]. Due to the unique physical and chemical properties and their being easy to synthesize and obtain, MWCNTs are broadly applied for the preparation of various composite materials [2, 3]. The electrical conductivity, thermal stability and mechanical strength of the composite, which included nanotubes and conjugated polymers, has been improved since plenty of work has been devoted to the development of see-through materials [4]. Especially after the combination of MWCNTs and conductive polymer PANI and other carbon nanomaterials, it can be used in supercapacitors [5] and effective adsorbents [6].  
The rapid development of new supercapacitor has been widely favored with energy storage devices, which contains many advantages such as large charge and discharge current, high power density and long cycle life [6]. The electrochemical performance of supercapacitors mainly depends on the electrode materials [7; 8], which are required to have a large specific surface area, excellent conductivity, rich pore size distribution and a stable structural system [9; 10]. With the high specific surface area of carbon nanotubes (CNTs), relatively high electrical conductivity and significant chemical stability [11; 12], it provides the possibility to prepare excellent electrochemically active materials [7]. However, the energy storage performance of CNTs is reduced dramatically by the defects of agglomeration resulting in bending and winding. Therefore, MWCNTs have been preliminarily functionalized. The bonds on the walls of MWCNTs are broken [13] and the specific surface area is increased with more active sites and better interface binding energy [14]. Therefore, the interaction between the surface and the conductive polymer modified layer is enhanced [2]. Among various conductive polymers, PANI has the advantages of easy preparation, low cost, reversibility [15; 16; 17] and good redox properties [17; 18; 19; 20]. In addition, PANI is an ideal choice for preparing composite materials with good electrical and optical properties [1; 21; 22], as well as good environmental stability [23; 24]. Nevertheless, the internal resistance and the volume expansion changes greatly in the process of using PANI, which makes the molecular chain of PANI breakdown and the performance of cycle stability insufficient [17; 25]. In view of this, the performance of composite materials shows better performance than single components, based on the excellent synergistic effect of the combination of CNTs and PANI [1; 26]. Similarly, with CNTs, the new type of carbon nanomaterial CQDs also have a large specific surface area [27] and good electrical conductivity [28]. In addition, it provides more space for electron transport and storage compared with CNTs.  
In this experiment, FMWCNTs @ CQDs @ PANI, a new type of carbon matrix composite material, was compounded by PANI, FMWCNT and CQDs with in-situ polymerization and the hydrothermal method. After successful preparation, the composite material was fabricated into an electrode material, and its electrochemical performance was characterized.