Preparation of hierarchically porous, heteroatom-rich nanostructured carbons through green and scalable routes plays a key role for practical energy storage applications. In this work, naturally abundant lignocellulosic agricultural waste with high initial oxygen content, hazelnut shells, were hydrothermally carbonized and converted into nanostructured ‘hydrochar’. Environmentally benign ceramic/magnesium oxide（Mg O） templating was used to introduce porosity into the hydrochar. Electrochemical performance of the resulting material（HM700） was investigated in aqueous solutions of 1 M H2SO4, 6 M KOH and1 M Na2SO4, using a three-electrode cell. HM700 achieved a high specific capacitance of 323.2 F/g in 1 M H2SO4（at 1 A/g,-0.3 to 0.9 V vs. Ag/Ag Cl） due to the contributions of oxygen heteroatoms（13.5 wt%）to the total capacitance by pseudo-capacitive effect. Moreover, a maximum energy density of 11.1 Wh/kg and a maximum power density of 3686.2 W/kg were attained for the symmetric supercapacitor employing HM700 as electrode material（1 M Na2SO4, E = 2 V）, making the device promising for green supercapacitor applications.
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机译：通过绿色和可扩展的路线制备分级多孔的，富含杂原子的纳米结构碳，对实际的储能应用至关重要。在这项工作中，将天然富集的具有高初始氧含量的木质纤维素农业废料，榛子壳进行了水热碳化，并转化为纳米结构的“水焦”。使用环境友好的陶瓷/氧化镁（Mg O）模板将孔隙率引入到烃中。使用三电极电池，研究了所得材料（HM700）在1 M H2SO4、6 M KOH和1 M Na2SO4的水溶液中的电化学性能。由于氧杂原子（13.5 wt％）对总电容的贡献，HM700在1 M H2SO4中达到了323.2 F / g的高比电容（相对于Ag / Ag Cl，在1 A / g，-0.3至0.9 V下，相对于Ag / Ag Cl）通过伪电容效应。此外，以HM700为电极材料（1 M Na2SO4，E = 2 V）的对称超级电容器的最大能量密度为11.1 Wh / kg，最大功率密度为3686.2 W / kg，使该器件有望用于绿色超级电容器应用程序。
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