Hierarchical hollow tubular fibrous brucite-templated carbons obtained by KOH activation for supercapacitors

Hierarchical hollow tubular porous carbons have been widely used in applications of supercapacitors, batteries, CO2 capture and catalysis due to their hollow tubular morphology, large aspect ratio, abundant pore structure and superior conductivity. Herein, hierarchical hollow tubular fibrous brucite-templated carbons (AHTFBC(s)) were prepared using natural mineral fiber brucite as the template and KOH as the chemical activator. The effects of different KOH additions on the pore structure and capacitive performance of AHTFBC(s) were systematically studied. The specific surface area and micropore content of AHTFBC(s) after KOH activation were higher than those of HTFBC. The specific surface area of the HTFBC is 400 m(2) g(-1), while the activated AHTFBC(5) has a specific surface area of up to 625 m(2) g(-1). In particular, compared with HTFBC (6.1%), a series of AHTFBC(s) (22.1% for AHTFBC(2), 23.9% for AHTFBC(3), 26.8% for AHTFBC(4) and 22.9% for AHTFBC(5)) with significantly increased micropore content were prepared by controlling the amount of KOH added. The AHTFBC(4) electrode displays a high capacitance of 197 F g(-1) at 1 A g(-1) and the capacitance retention of 100% after 10 000 cycles at 5 A g(-1) in the three-electrode system. And an AHTFBC(4)//AHTFBC(4) symmetric supercapacitor exhibits the capacitance of 109 F g(-1) at 1 A g(-1) in 6 M KOH and an energy density of 5.8 W h kg(-1) at 199.0 W kg(-1) in 1 M Na2SO4 electrolyte. In addition, the capacity retention of AHTFBC(4) in the symmetric supercapacitor was maintained at 92% after 5000 cycles in both 6 M KOH and 1 M Na2SO4 electrolytes.