Journal of Electronic Materials ( IF 2.2 ) Pub Date : 2021-07-31 , DOI: 10.1007/s11664-021-09098-x Lorena Cuéllar-Herrera 1 , Elsa Arce-Estrada 1 , Antonio Romero-Serrano 1 , José Ortiz-Landeros 1 , Cindy Tirado-López 1 , Aurelio Hernández-Ramírez 1 , Josué López-Rodríguez 1 , Román Cabrera-Sierra 2
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Two hydrothermal techniques under microwave irradiation were used to synthesize γ-MnO2 from 90°C to 150°C in 10−30 min. The first technique is based on reducing KMnO4 with MnSO4, and the second one involves liquid-phase oxidation between MnSO4 and (NH4)2S2O8. The structures and morphologies of the samples were analyzed using X-ray diffraction, scanning electron microscopy, and N2 physisorption measurements. The electrochemical properties were evaluated through cyclic voltammetry and electrochemical impedance spectroscopy. The γ-MnO2 materials obtained by the first technique mainly exhibited nanorods with diameters of 40–60 nm, and the samples obtained by the second technique showed flower-like microspheres with diameters of 1−2 µm; each flower was composed of nanosheets with a thickness of 10−20 nm. The processing time directly depends on the size of the nanorods. The sample synthesized by the first technique at 150°C and 10 min has the highest specific surface area of up to 59.08 m2 g−1 and mean pore diameter of 34.11 nm. Furthermore, this sample exhibits a near-rectangular cyclic voltammetry curves and high specific capacitance of 331.3 F g−1 in 0.1 M Na2SO4 solution at 5 mV s−1 scan rate.
Graphic abstract
中文翻译：
用于高性能超级电容器的 γ-MnO2 的微波辅助合成和表征
在微波辐射下使用两种水热技术在10-30 分钟内从90°C 到150°C合成γ-MnO 2。第一种技术基于用 MnSO 4还原 KMnO 4，第二种技术涉及 MnSO 4和 (NH 4 ) 2 S 2 O 8之间的液相氧化。使用X 射线衍射、扫描电子显微镜和N 2物理吸附测量分析样品的结构和形态。通过循环伏安法和电化学阻抗谱评估电化学性能。γ-MnO 2第一种技术获得的材料主要表现出直径为40-60 nm的纳米棒，第二种技术获得的样品表现出直径为1-2 μm的花状微球；每朵花由厚度为 10-20 nm 的纳米片组成。处理时间直接取决于纳米棒的尺寸。通过第一种技术在 150°C 和 10 分钟下合成的样品具有高达 59.08 m 2 g -1的最高比表面积和 34.11 nm 的平均孔径。此外，该样品在5 mV s -1扫描速率下在0.1 M Na 2 SO 4溶液中表现出接近矩形的循环伏安曲线和331.3 F g -1 的高比电容。
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