###### Abstract  
Hydrothermally obtained \(\alpha\)-MnO\({}_{2}\) nanowire characterizations confirm the tetragonal crystalline structure that is several micrometers long and 20-30 nm in diameter with narrow distributions in their dimensions. The absorption calculated from diffuse reflectance of \(\alpha\)-MnO\({}_{2}\) occurred in the visible region ranging from 400 to 550 nm. The calculated band gap with Quantum Espresso using HSE approximation is -2.4 eV for the ferromagnetic case, with a slightly larger gap of 2.7 eV for the antiferromagnetic case, which is blue-shifted as compared to the experimental. The current work also illustrates the transformations that occur in the material under heat treatment during TGA analysis, with the underlying mechanism. Electrochemical studies on graphite supports modified with \(\alpha\)-MnO\({}_{2}\) compositions revealed the modified electrode with the highest electric double-layer capacitance of 3.444 mF cm\({}^{-2}\). The degradation rate of an organic dye--broadamine B (RhB)--over the compound in an acidic medium was used to examine the catalytic and photocatalytic activities of \(\alpha\)-MnO\({}_{2}\). The peak shape changes in the time-dependent visible spectra of RhB during the photocatalytic reaction were more complex and progressive. In two hours, RhB degradation reached 97% under sun irradiation and 74% in the dark. cap  
charge accumulation, and pseudocapacitors, in which the electrical charges are mainly stored by fast and reversible redox reactions [3; 4]. EDLC can provide ultrahigh power and excellent cycle life because of the fast and non-degradation process between active electrode materials and electrolytes. However, the energy stored in EDLCs is limited by the finite electrical charge separation at the electrode materials/electrolyte interface and the availability of electrode surface area. Because of the Faradaic process underpinning the energy stored in a pseudocapacitor, it has increased energy density but at the cost of power density and cycle life compared to EDLCs [5]. The combination of their properties and their simple structure, high power density, fast charging, and pollution-free effect makes supercapacitors a new generation of green energy storage devices with higher output power and longer life than lithium-ion batteries [6; 7]. The typical electrode materials used for pseudocapacitors are transition metal oxides/hydroxides. The different transition metal oxides with pseudo-capacitive behaviors include iron-based supercapacitors [8] and RuO\({}_{2}\)-based ones, which generally have several redox states or structures and contribute to charge storage by fast Faraday charge transfer between the different redox states [9]. MnO\({}_{2}\) stands out as one of the most promising electrode materials because of its natural abundance, low cost and toxicity, environmental friendliness, and high theoretical specific capacitance (of 1370 F/g), and because it presents various oxidation states that benefit from efficient redox charge transfer to satisfy the needs of energy storage with a long-life cycle [10]. When formed in single-phase, tetragonal MnO\({}_{2}\) can incorporate different cations, as well as water molecules inside the \"tunnels\" or \"channels\" between the [MnO\({}_{6}\)] octahedra. \(\alpha\)-MnO\({}_{2}\) stabilizes in a body-centered tetragonal lattice among manganese dioxides (I4/m(87), a = 9.96 A; c = 2.85 A (2 \(\times\) 2) tunnel type), while, B-MnO\({}_{2}\) crystallizes as the pure tetragonal/rutile structure (P4\({}_{2}\)/mmm, a = 4.39; c = 2.87 A (1 \(\times\) 1) tunnel) [11; 12]. MnO\({}_{2}\) is one of the most appealing materials because of its technological significance and potential applications in various catalytic and electrochemical processes where their properties are significantly influenced by its structure and morphology, allowing researchers to investigate the effect of the support structure on catalytic activity [13].