## 3 Results and Discussion
From Figure 4a, we can see that the size of nano-particles is not uniform and the Staghorn coral-like structure appears quite dense. A dense structure such as that of Sample B might limit the access of electrolyte molecules if the materials are used as an electrode in electrochemical supercapacitors. Figure 2: XRD of MnO\({}_{2}\) synthesized at different conditions: Sample A: after grinding; Sample D: acid treated for 40 h at 25 \({}^{\circ}\)C; Sample E: reacted at 80 \({}^{\circ}\)C for 3 h. (* \(\alpha\)-MnO\({}_{2}\)). Further development of these microstructures was realized by treating Sample A in acid at 25 \({}^{\circ}\)C for a slightly longer time, i.e., 20 h, to form Sample C. The packed nano-particles elongated in one direction and the Staghorn coral-shaped microstructure developed a hollow structure, as shown in Figure 3b. For Sample D, the reaction time was increased to 40 h, and its morphology is present in Figure 3c. Nano-rods of uniform size are packed together to form a hollow Staghorn coral-shaped microstructure. As we can see in the high magnification image in Figure 4b for Sample D, the rod-like particles are expanded in one direction at the expense of other directions compared to Sample B and C. From Table 1, we can infer that Sample D has a reduced BET surface area, compared to Sample B, possibly due to the elongation of one dimension to form nanorods. Nevertheless, by comparing \begin{table}
\begin{tabular}{c c c} \hline \hline
**Samples** & **BET Surface Area (m\({}^{2}\)/g)** & **Average Pore Diameter @Max. Volume (nm)** & **Total Pore Volume (mL/g)** \\ \hline Sample B & 220 & \(\sim\)13 & 0.7 \\ Sample C & 200 & 10-30 & 0.7 \\ Sample D & 190 & 10-30 & 0.8 \\ Sample E & 160 & N/A & 0.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: BET surface areas, average pore diameters, and total pore volumes for each studied sample. Figure 4: High resolution SEM images of samples treated at various conditions: (**a**) 15 h at 25 \({}^{\circ}\)C (Sample B); (**b**) 40 h at 25 \({}^{\circ}\)C (Sample D). Figure 3: SEM images of fours samples treated at various conditions: (**a**) 15 h at 25 \({}^{\circ}\)C (Sample B); (**b**) 20 h at 25 \({}^{\circ}\)C (Sample C); (**c**) 40 h at 25 \({}^{\circ}\)C (Sample D); and (**d**) 3 h at 80 \({}^{\circ}\)C. (Sample E). Figure 4a,b, we can see that Sample D preserves the same surface features on nano-sized building blocks as Sample B. We believe that such a surface feature and the hollow microstructure of Sample D provide more active sites to the electrochemical system, benefiting electrochemical reactions. The temperature effect on the shape and morphology of the synthesized materials was examined by SEM for Sample E (refer to Figure 1 for sample notation), as shown in Figure 3d. Instead of a Staghorn coral shape, a bird's nest-shaped microstructure was developed in this process. The nano-sized building block turns to nanofibres rather than nanorods that are seen in Sample D. This implies that Sample E is under an accelerated growth process compared with the samples produced at 25 \({}^{\circ}\)C. The BET surface area of Sample E is the smallest among all the samples, as we can see in Table 1. The reduction of BET surface areas could be attributed to the further elongation of nano-sized building blocks to form the nanofibres when Sample E is generated. Figure 1 illustrates the morphologies of \(\alpha\)-MnO\({}_{2}\) developed at different synthetic conditions for Samples B, C, D, and E. It demonstrates that, at 25 \({}^{\circ}\)C, Sample A gradually developed into different shapes as the reaction time proceeded. The process in the solution phase provides the mechanism by which the growth rate is controlled; consequently, the nanostructured substance, such as nanorods, can be developed with detailed surface features. Such a nanostructure can be further assembled into sophisticated micro-buildings, such as the Staghorn coral-like microstructure, while the fine features on the surface are kept.