# Porous Doped Carbons from Anthracite for High-Performance Supercapacitors
## 3 Results and Discussion  
### Effect of Thermal Treatment upon Supercapactor Performance  
In order to investigate the impact of thermal treatment upon the textural properties of the porous carbons, the N\({}_{2}\) adsorption/desorption isotherm profiles are measured. As seen from Figure 1, the isotherms are typical of type I, demonstrating that the porosity mainly originates from micropores, which is beneficial for ion storage during the charge/discharge process [20]. In the whole pressure region, the largest nitrogen adsorption volume of KAC-800 verifies its highest SSA. Detailed information on the textural properties of all samples is compiled in Table 1. The KAC-800 sample shows a high SSA of 2814 m\({}^{2}\) g\({}^{-1}\) with a pore volume of 1.531 cm\({}^{3}\) g\({}^{-1}\), which is higher than KAC-700 and KAC-900. The specific surface area contributed by the micropore filling is 1568 m\({}^{2}\) g\({}^{-1}\) for KAC-700, 1935 m\({}^{2}\) g\({}^{-1}\) for KAC-800, and 1658 m\({}^{2}\) g\({}^{-1}\) for KAC-900. The corresponding PSD is delineated in Figure S1. It can be seen that the PSD curves of samples mainly reveal the existence of micropores and small mesopores with a size of 1-4 nm. The average pore size (d\({}_{\text{M}}\)) is made larger with the increase in the activation temperature. As has been evidenced, the coexistence of micro/meso-scale pores is critically vital for attaining the rapid ion transportation and high-power characteristics of supercapacitors [21; 22]. It is obvious that structural signatures of porous carbons heavily hinge upon the activation temperature. The textural evolution here unveils that the activation temperature can function as an effective rudder to fine-tune the material structure and thus exert the striking ramifications upon the supercapacitor performance of the porous carbon electrodes. Supercapacitive performances of the samples firstly came under evaluation in a three-electrode system by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) in 6 M KOH (Figure 2). The CV curves of all samples (Figure 2a) present rectangular-like shapes with signally broadened redox peaks, illuminating that the overall capacitance originates from a good combination of double-layer capacitance and pseudocapacitance contributed from nitrogen functional groups [16]. Moreover, the largest CV area of the KAC-800 may be associated with the greatest SSA of the sample activated at 800 \({}^{\circ}\)C, which can provide plenty of the electron/ion-active interfaces [23]. The exact specific capacitances quantified from GCD tests are displayed in Figure 2b. Notably, the KAC-800 electrode always delivers the highest capacitance at different current densities spanning between 0.5 and 20 A g\({}^{-1}\), with the specific capacitances of 325 and 216 F g\({}^{-1}\) being accomplished at 0.5 and 20 A g\({}^{-1}\), respectively. Moreover, it is clear that the specific capacitances for all samples encounter a gradual decrease with the rise in the current density because of the remarkable gain in the diffusion limitation inside pore channels [24]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Samples** & \begin{tabular}{c} **S\({}_{\text{BET}}\)** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **V\({}_{\text{T}}\)** \\ **(cm\({}^{3}\) g\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **d\({}_{\text{M}}\)** \\ **(nm)** \\ \end{tabular} \\ \hline KAC-700 & 2041 & 1.095 & 2.145 \\ KAC-800 & 2814 & 1.531 & 2.177 \\ KAC-900 & 2337 & 1.319 & 2.223 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Textural properties of samples (calculated total surface area \(S_{\text{BET}}\), total pore volume \(V_{\text{T}}\), and average pore diameter \(d_{\text{M}}\)). Figure 1: N\({}_{2}\) adsorption-desorption isotherms of samples. Figure 3a portrays the CV profiles of KAC-800 under varying scan rates.