## 3 Results and Discussions
### Electrochemical Measurements  
The electrochemical study conducted on graphite supports modified with compositions containing \(\alpha\)-MnO\({}_{2}\) led to the identification of the modified electrode with the highest electric double-layer capacitance.  
The capacitive current density (i\({}_{\text{dl}}\)) was calculated using Equation (4) and the value of the electric double-layer capacitance (C\({}_{\text{dl}}\)), defined as the capacitance resulting from stored charge in the double-layer region at the electrode/electrolyte solution interface [61], was the absolute value of the slope obtained for the linear dependence between i\({}_{\text{dl}}\) and the scan rate [62; 63].  
\[\text{i}_{\text{dl}}=(\text{i}_{\text{a}}+\text{i}_{\text{c}})/2 \tag{4}\]  
where i\({}_{\text{dl}}\) (A cm\({}^{-2}\)) is the capacitive current density; i\({}_{\text{a}}\) (A cm\({}^{-2}\)) and i\({}_{\text{c}}\) (A cm\({}^{-2}\)) are the absolute values of the anodic and cathodic current densities, for a given scan rate, at a potential value where only double-layer adsorption and desorption features are present [64; 65; 66].  
Figure 9a,b show the graphical representations of the dependence between the capacitive current density and the scan rate for the electrodes considered in the study, based on cyclic voltammograms recorded in 0.1 mol L\({}^{-1}\) KCl electrolyte solution. The C\({}_{\text{dl}}\), R\({}^{2}\), roughness factor (R\({}_{\text{f}}\)) and electrochemically active surface area (EASA) values obtained for all samples are displayed in Table 3.  
Figure 8: Thermal gravimetric analysis (left) and DTA (right) curves for the powder MnO\({}_{2}\) type \(\alpha\)-MnO\({}_{2}\) synthesized using the hydrothermal method.  
The highest C\({}_{\text{dl}}\) value was determined for G\({}_{\text{MnO2-v-EDH}}\), in which case the slope of the linear dependence between i\({}_{\text{dl}}\) and \(v\) was equal to 3.444 mF cm\({}^{-2}\). The C\({}_{\text{dl}}\) value can also be expressed in mF by taking into account the geometrical surface of the working electrode, and for the mentioned sample it is 0.964 mF. The linear increase in i\({}_{\text{dl}}\) with the scan rate indicates the charging and discharging of the Helmholtz double-layer [67] and that the composition applied on the surface of the graphite support acted as a simple capacitor in the scanned potential range [68].  
A similar C\({}_{\text{dl}}\), of 3.41 mF cm\({}^{-2}\), was obtained for G\({}_{\text{MnO2-v-DMF}}\), but in this case the R\({}^{2}\) value was quite small (0.9584).  
To estimate the roughness factor, defined as the ratio between the real and geometric surface areas, the C\({}_{\text{dl}}\) values of the studied electrodes were divided by 60 uF cm\({}^{-2}\), which is usually considered as the specific capacitance of a smooth oxide surface [69]. The EASA was  
Figure 9: (a) The plot of the dependence between i\({}_{\text{dl}}\) and \(v\) for the bare electrode and for the electrodes modified using suspensions in ethanol. (b) The plot of the dependence between i\({}_{\text{dl}}\) and \(v\) for the electrodes modified using suspensions in DMF.  
estimated by expressing the C\({}_{\text{dl}}\) value in mF and dividing it by the specific capacitance [62]. The highest R\({}_{\text{f}}\) and EASA values were calculated for G\({}_{\text{MnO2-V-EOH}}\).  
Since the electrochemical characterization of the modified electrodes is in terms of their electric double-layer capacitance, and a parameter of importance in the field of supercapacitors [70] revealed that the highest value belonged to G\({}_{\text{MnO2-V-EOH}}\), it can be concluded that out of the investigated samples this electrode is the most likely to find application in the respective domain. However, for a conductive support modified with the synthesized \(\alpha\)-MnO\({}_{2}\) nanowires in a mixture with Vulcan carbon to actually be used in supercapacitors, further studies are required that include the testing of different deposition methods and amounts of materials.