Carbon microsphere from water hyacinth for supercapacitor electrode

In this study, water hyacinth was hydrolyzed to sugars with dilute sulphuric acid (0.25 M) under subcritical water conditions (P = 20 bar, T = 130 °C) for 2 h. The sugar solution was then carbonized under subcritical conditions to produce carbon microsphere. The subcritical water carbonization was conducted at 40 bar and various temperatures (160-200 °C) and times (6-10 h). The highest yield of carbon microspheres was 0.1019 g/g dry water hyacinth at the temperature of 200 °C for 10 h. The carbon microsphere was activated using a combination of chemical (KOH solution) and physical (microwave) treatments to increase the specific surface area and porosity of carbon microsphere. Electrocapacitive study of carbon microspheres showed that the carbon microsphere activated at impregnation ratio of 1:1 and microwave power of 630 W has the highest specific capacitance and excellent electrochemical stability.