Microstructure and electrochemical double-layer capacitance of carbon electrodes prepared by zinc chloride activation of sugar cane bagasse

Activated carbons for supercapacitor electrodes are prepared from sugar cane bagasse using chemical activation with ZnCl2. The ZnCl2 activation of bagasse is studied using thermogravimetric analysis and the carbon pore structures are characterised using N2 and CO2 adsorption. In two-electrode, sandwich-type supercapacitor cells containing 1 M H2SO4 the sugar cane bagasse carbons (SCCs) exhibit specific energy up to 10 Wh kg−1 and specific capacitance close to 300 F g−1. The electrochemical performance of the SCCs is attributed to their high specific surface area and the development of mesopores with ZnCl2 impregnation ratios of 1 or greater. By contrast, the pyrolysis of bagasse without ZnCl2 produces a carbon with low specific capacitance. The SCC prepared with a ZnCl2 ratio of 3.5 shows the most stable electrochemical performance at fast charge–discharge rates.