Capacitive Behaviours of Phosphorus-Rich Carbons Derived from Lignocelluloses

A series of phosphorus and oxygen enriched carbons prepared by phosphoric acid activation of the lignocellulosic waste, fruit stones, are studied as the electrodes of supercapacitor in 1 M H2SO4 electrolyte. The microstructure and surface properties of the carbons are characterized by N2 and CO2 sorptions and X-ray photoelectron spectroscopy (XPS), respectively. Cyclic voltammetry, galvanostatic charge/discharge and wide potential window test are carried out to evaluate the electrochemical performances of the carbon electrodes. Statistical analysis is employed to confirm the limitation of the operation potential of the supercapacitors. The results show that the sample with balanced porous structure and higher phosphorus content exhibits a specific capacitance of 165 F g−1, delivers an energy density of 13 Wh kg−1 at an operation window of 1.5 V, and shows stable cycling performance with a retention ratio of 99% even after 20000 cycles. This work suggests that the adjusted pore structure and surface functional groups which influenced the capacitive performance of the carbon electrode can be finely adjusted by the activation temperature.