Rice husk-derived porous carbons with high capacitance by ZnCl2 activation for supercapacitors

Rice husk, a renewable agricultural by-product, was used as a precursor for the fabrication of high performance porous carbons for supercapacitors by ZnCl2 activation with or without microwave-assisted heating. Microporous carbons with the surface area bigger than 1442 m2/g are made at a ZnCl2/rice husk mass ratio as low as 1/1 from rice husk, which is really worthwhile from the viewpoint of economic, environmental and societal issues. Mesoporous carbons with high surface area and mesopore percentage are made in one-step ZnCl2 activation process by microwave-assisted heating, and the supercapacitors based on mesoporous carbons show high energy density and excellent rate performance in 6 M KOH electrolyte. The specific capacitance of rice husk-derived mesoporous carbons made by conventional heating retains 243 F/g after 1000 charge–discharge cycles. The findings suggest a simple yet efficient approach to producing cost-effective porous carbons with high performance for supercapacitors.