Hierarchical porous carbon based on the self-templating structure of rice husk for high-performance supercapacitors

Using the self-templating structure of rice husk (RH), hierarchical porous carbon with high surface area was prepared by carbonization, NaOH-leaching and KOH activation. The formation processes of the hierarchical porous structure were discussed in detail, where the silica in RH plays a crucial role. The rice husk-based hierarchical porous carbon (RHHPC) with a 3D porous structure, was composed of macrochannels, mesopores and micropores both on its surface and inner channels. The RHHPC exhibited a surface area as high as 2804 m2 g−1 and a high-level of oxygen-containing groups (with an oxygen content of 9.74 at%). The high surface area, large amount of oxygen-containing groups and unique hierarchical porous structure endow the RHHPC with a high capacitance (278 F g−1 at 0.5 A g−1) and excellent rate capability (77.2% retention at 20 A g−1) in 6 mol L−1 KOH. Furthermore, the symmetric supercapacitor fabricated with RHHPC delivered a high energy density of 7.4 W h kg−1 at a power density of 6195 W kg−1, which reveals the promising application of RHHPC in high-performance supercapacitors.