MnO₂ nanostructures with different morphologies (nanowires, nanowire bundles and flower-like nanosheet bundles) were synthesized by adjusting the concentration of KMnO₄ solution using a simple and surfactant-free hydrothermal method. Both MnO₂ nanowires and nanosheets have ultrathin thickness of about 10–30 nanometers. Such ‘open’ nanostructures can facilitate the electrolyte infiltration and increase the active material utilization efficiency. Owing to the high electron conductivity of the graphene/Ni foam (GNF) substrate as well as the large electrolyte/electrode contact interface, a specific capacitance of 201 F g⁻¹ can be obtained in 1 M Na₂SO₄ electrolyte. An asymmetric supercapacitor assembled with flower-like MnO₂ nanosheet bundles on GNF and activated microwave exfoliated graphite oxide (a-MEGO) yields an energy density of 44.5 W h kg⁻¹ and a power density of 50.0 kW kg⁻¹, respectively. These unique and controllable MnO₂ nanostructures may have enormous potential applications in the fields of energy storage and sensors.

中文翻译：

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高性能不对称超级电容器的锚固在不同形态的石墨泡沫上 的MnO ₂纳米结构的可控合成†

通过使用简单且无表面活性剂的水热法调节KMnO ₄溶液的浓度，合成了具有不同形态（纳米线，纳米线束和花状纳米片束）的MnO ₂纳米结构。MnO ₂纳米线和纳米片都具有约10–30纳米的超薄厚度。这种“开放”的纳米结构可以促进电解质的渗透并提高活性物质的利用效率。由于石墨烯/ Ni泡沫（GNF）衬底的高电子电导率以及大的电解质/电极接触界面，在1 M Na ₂ SO _4中可以得到201 F g ^-1的比电容。电解质。在GNF上组装有花状MnO ₂纳米片束和活化微波剥落的氧化石墨（a-MEGO）的不对称超级电容器，其能量密度分别为44.5 W h kg ^-1和50.0 kW kg ^-1。这些独特且可控的MnO ₂纳米结构在储能和传感器领域可能具有巨大的潜在应用。