Preparation of Hierarchical Porous Carbon from Wheat Bran for Free-Standing Electrode of High Areal Capacitance Supercapacitor

It is impressive that biomass gives out another option for carbon electrode fabrication in supercapacitors which has low cost and sustainable source. In this work, waste of wheat bran was used to synthesize porous carbon via alkali activation. Under mass ratio of NaOH/precursor as 4, the wheat bran carbon presented hierarchical hexagon pores with prominent surface area of 2562 m(2) g(-1). Utilizing two symmetrical free-standing electrodes, the as-prepared carbon exhibited gravimetric capacitance of 294.3 F g(-1) at 0.5 A g(-1) and cyclic life of 94 % for 50,000 cycles at 2 A g(-1), while commercial carbon showed 269.7 F g(-1) and 75 % stability under the same condition. With large mass loading of 20 mg cm(-2), the wheat bran carbon revealed superior areal capacitance of 3.08 F cm(-2), and the value could still maintain as 2.80 F cm(-2) over 10,000 cycles. Consequently, the wheat bran has been found as a promising precursor for advanced carbon electrode.