Development of carbon electrodes and electrochemical double-layer supercapacitors using agricultural crop residue biomass-derived porous carbon

Abstract The development of cost-effective and efficient energy-storage devices, such as supercapacitors with enhanced electrochemical properties, is highly needed for the future. Therefore, the highly porous surface area of wheat straw, which is activated carbon (AC) derived through chemical activation, is being used to develop electrodes. AC with a surface area of 1093.46 m2/g was used for electrode fabrication by mixing proportions of 80%, 90%, 100%, and 0% AC with polyvinylidene fluoride and N-methyl-2-pyrrolidone solution on different current collectors such as copper, stainless steel, and aluminum. The electrochemical analysis of the developed electrodes and symmetric electrochemical double-layer capacitors was performed against a silver/silver chloride reference electrode by using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The specific capacitance of the electrodes, as shown in cyclic voltammogram curves, is 305.2, 287, and 256.2 F/g. The galvanostatic charge–discharge curves display 281, 244.5, and 226.5 F/g at 0.5 A/g, and 247, 206, and 189 F/g at 1 A/g for copper, aluminum, and stainless steel current collectors, respectively. The symmetric electrochemical double-layer capacitors, made with 90% AC and copper current collectors, exhibited quasi-rectangular curves with specific capacitances of 219.4, 172.7, and 132.4 F/g. Different areas of the current collector in supercapacitors increase the active material deposit, enabling more charge and ions to accumulate, resulting in improved charge-transfer resistance.