Hydrothermal conversion of lignocellulosic biomass into high-value energy storage materials

摘要

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 (MgO) templating was used to introduce porosity into the hydrochar.Electrochemical performance of the resulting material (HM700) was investigated in aqueous solutions of 1 M H2SO4,6M KOH and 1 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.gv vs.Ag/AgCl) due to the contributions of oxygen hetematoms (13.5wt％)to the total capacitance by pseudo-capacitive effect.Moreover,a maximum energy density of 1L1 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.