Green synthesis of activated carbons from machine-made Hanji as carbon precursor for high-rate supercapacitor and excellent sensor applications

Herein, machine made Hanji (MMH) was applied as a precursor for the preparation of cost-effect and highly efficient activated carbon (AC) materials for supercapacitor and sensors applications. Activated carbon (AC) materials were derived from Hanji (traditional Korean paper), using different activation methods such as KOH and steam activation, and the obtained carbon products were designated as KHCs and SHCs, respectively. The KHCs and SHCs showed different specific surface areas (KHCs: 1945.6 m² g^-1 and SHCs: 1143.3 m² g^-1) and mesopore volume % (KHCs: 2.2 % and SHCs: 37.1 %), indicating that the choice of activation method can significantly influence the textural properties. The as-prepared KHCs and SHCs delivered the maximum capacitance values of 105.6 F g^-1 and 60 F g^-1, respectively. The AC materials were further utilized as sensing platform for electrochemical detection of vanillin (VN) detection. It demonstrated good electro-catalytic properties towards VN electrooxidation with high sensitivity, and detection range. The enhanced performance of KHCs (supercapacitors) and SHCs (vanillin detection) is due to the presence of different mesoporous volume, surface area, and catalytic properties. In particular, a high energy storage performance of KHCs is due to the fact that the large surface area and less mesoporous volume promote the ionic absorption characteristics.