High Yield and High Volumetric Capacitance Activated Carbons by One-step Homogeneous Activation of Diaphragma Juglandis Fructus for Supercapacitors

Diaphragma juglandis fructus (DJF) is selected as a precursor of activated carbon (AC). Saturated absorption of solution containing desirable amount of KOH in DJF leads to one-step homogeneous activation which produces AC-1 comprising non-honeycombed smaller particles with lower energy consumption compared with AC-2 by the conventional two-step method. The non-honeycombed morphology of AC-1 results in a high yield of 24.2 % and a high packing density of 0.78 g cm-3. Although the specific surface area of AC-1 is only 1030 m2 g-1, the specific capacitance reaches 244 F g-1 at 0.5 A g-1 in 6 mol L-1 KOH in a three-electrode cell, higher than that of AC-2 due to the reasonable pore distribution. In a symmetrical supercapacitor with the 6 mol L-1 KOH electrolyte, the maximum specific cell capacitance is 58.1 F g-1 at 0.25 A g-1, corresponding to a high volumetric capacitance of 181 F cm-3 for a single electrode. The flexible supercapacitor with PVA/KOH electrolyte shows areal capacitance of 637 mF cm-2 and can maintain 70 % of the initial value after 180 & DEG; bending for 400 times. The AC-1 cell with the ionic liquid electrolyte has a maximum specific energy of 30.6 Wh kg-1, which can illuminate 16 light-emitting diodes simultaneously. Diaphragma juglandis fructus derived activated carbons by one-step homogeneous activation shows a high yield of 24.2 % and a high packing density of 0.78 g cm-3, resulting in a high volumetric capacitance of 181 F cm-3. The flexible supercapacitor can maintain 70 % of 637 mF cm-2 after 180 & DEG; bending for 400 times. The AC-1 cell in ionic liquid has a maximum specific energy of 30.6 Wh kg-1, illuminating 16 light-emitting diodes simultaneously.+image