## 3 Results and Discussion  
The scheme adopted to design and develop the printed MWCNTs/AC/BNNTs ternary composite material is well described in the experimental section and also is shown in Figure 1. An optical image of the printed MWCNTs/AC/BNNTs ternary composite material is illustrated in Figure 2. The film was printed on the 316-SS sheet with the aid of 3D DIW technique by applying the suitable printing conditions (discussed in detail in experimental section). Furthermore, the FE-SEM microstructural characterizations of the MWCNTs/AC/BNNTs ternary composite material at various magnifications are illustrated in Figure 3.  
Figure 2: Optical image of the printed MWCNTs/AC/BNNTs ternary composite material. We can observe spherical and tubular-like structures of the claimed MWCNTs/AC/BNNTs ternary composite material. The tubular-like structures are associated with MWCNTs and BNNTs, while the spherical morphology in the FESEM images indicates the presence of AC. The multicomponent design was beneficial to develop the high-performance MWCNTs/AC/BNNTs composite electrode material, where each component contributed individually as well as working as a multicomponent system with enhanced synergistic interaction during the electrochemical reaction. The presence of the tubular-like structures of MWCNTs and BNNTs were beneficial enough to reduce the agglomeration phenomena of the AC spherical particles and to achieve high electrochemical performance of the MWCNTs/AC/BNNTs composite electrode material. The crystallinity level of the possible phases of MWCNTs/AC/BNNTs composite material was investigated through an XRD analysis (Figure 4a). The peaks appearing at the 20 position of 25.48\({}^{\circ}\) and 42.49\({}^{\circ}\) represent crystal planes (002) and (100) of the typical graphitic carbon structure [21,22]. In addition, the BNNT crystal planes (002) and (101) also appear at the same 20 positions of 25.48\({}^{\circ}\) and 42.49\({}^{\circ}\), respectively [23,24]. Thus, the highly crystalline structure of the as-synthesized MWCNTs/AC/BNNTs ternary composite material is verified by the XRD analysis. Raman spectroscopy is an important tool to analyze the crystalline quality index of carbon-based materials such as MWCNTs. The two typical bands, i.e., the \"D\" and \"G\" bands, have appeared in the typical Raman spectra (Figure 4b) of the MWCNTs/AC/BNNTs ternary composite material. The respective bands have appeared at the Raman shift (cm\({}^{-1}\)) positions of 1334 and 1563.84, respectively, and indicate the presence of incompletely graphitized carbon atoms. The high intensity of the G-band peak in comparison to the D-band peak clearly indicates a high crystallinity level of the as-synthesized MWCNTs-based composite electrode material. The ratio between I\({}_{\text{D}}\)/I\({}_{\text{G}}\) was estimated to be 0.85. Furthermore, the BET surface area and pore size of AC, MWCNT and BNNT was analyzed by the nitrogen adsorption-desorption isotherm method with the help of Brunauer-Emmett-Teller (BET) technique and detailed results are presented in (Figure 4c-e) and Table 1. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **BET Surface Area (m\({}^{2}\) g\({}^{-1}\))** & **Size of Pore (Å)** & **Pore Volume (cm\({}^{3}\) g)** \\ \hline Multiwalled carbon & 62.0763 & 201.7726 & 0.313132 \\ nanotubes & 271.7288 & 365.4881 & 2.482841 \\ Boron nitride nanotubes & 54.6504 & 202.8095 & 0.277091 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physical properties of activated carbon, multiwalled carbon nanotubes and boron nitride nanotubes. Figure 3: (a,b) FE-SEM images of the MWCNTs/AC/BNNTs ternary composite material at different magnifications.