In this study, we investigate the influence of calcination temperature on the structural, optical, and electrochemical properties of MnO nanoparticles synthesized through a chemical co-precipitation route. Field-Emission Scanning Electron Microscopy (FESEM) images depict the formation of highly agglomerated, spherical-shaped particles. At calcination temperatures of 700 °C and 900 °C, the observation reveals the emergence of flat pellets and rod-like structures. The X-ray Diffraction (XRD) patterns confirm the presence of the MnO phase in M and M samples. However, the sample calcined at 500 °C (M) showed a mixed phase of MnO and MnO. Upon further calcination at 700 and 900 °C, this mixed phase undergoes complete transformation into the MnO phase. The change in absorption onset and photoluminescence intensity of samples is found with an increase in calcination temperature due to the crystal growth and phase modification. Furthermore, the synthesized samples are employed as electrode materials for supercapacitor applications. The sample calcined at 300 °C (M) in three-electrode system demonstrated the specific capacitance (C) of 273.3 F/g at 0.5 A/g in an alkaline medium. The asymmetric cell assembled by using M and stem-derived carbon material (HBC-900) delivered higher C of 205.7 F/g at 0.5 A/g. In addition, asymmetric supercapacitor device exhibited a high energy and power density of 43.1 Wh/kg and 476.2 W/kg with 82.07 % of initial C retention over 10,000 cycles at 10 A/g, which makes the sample M as the potential electrode material for supercapacitor application.

中文翻译：

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氧化锰 (Mn3O4) 纳米颗粒的光学和电化学特性：研究煅烧温度对超级电容器性能的影响

在本研究中，我们研究了煅烧温度对通过化学共沉淀途径合成的 MnO 纳米粒子的结构、光学和电化学性能的影响。场发射扫描电子显微镜 (FESEM) 图像描绘了高度团聚的球形颗粒的形成。在 700 °C 和 900 °C 的煅烧温度下，观察结果显示出现扁平颗粒和棒状结构。 X 射线衍射 (XRD) 图证实 M 和 M 样品中存在 MnO 相。然而，在 500 °C (M) 下煅烧的样品显示出 MnO 和 MnO 的混合相。在 700 和 900 °C 进一步煅烧后，该混合相完全转变为 MnO 相。由于晶体生长和相变，随着煅烧温度的升高，发现样品的吸收起始和光致发光强度发生变化。此外，合成的样品还可用作超级电容器应用的电极材料。在三电极系统中于 300 °C (M) 下煅烧的样品在碱性介质中在 0.5 A/g 下表现出 273.3 F/g 的比电容 (C)。使用 M 和茎衍生碳材料 (HBC-900) 组装的不对称电池在 0.5 A/g 下具有 205.7 F/g 的更高 C。此外，非对称超级电容器装置在10 A/g下经过10,000次循环后表现出43.1 Wh/kg和476.2 W/kg的高能量和功率密度，初始C保留率为82.07%，这使得样品M成为潜在的电极材料超级电容器应用。