Preparation of highly porous carbon through activation of NH4Cl induced hydrothermal microsphere derivation of glucose

There is considerable interest in the synthesis of activated carbons from biomass through hydrothermal carbonization (HTC) followed by activation. Here we report our findings that using NH4Cl additive for HTC of glucose changes the product from nanosphere carbon to N-doped microsphere carbon with a much lower surface area, but unexpectedly, the following KOH-activated N-doped microsphere carbon shows a significantly higher specific surface area (exceeding 3000 m(2) g(-1)) than that (2385 m(2) g(-1)) of activated conventional HTC carbon. Under similar conditions, other HTC additives, such as NaCl and HCl, can also lead to the formation of microsphere carbons with decreased surface area, but the specific surface area of the corresponding activated carbons decreased accordingly. These comparisons together with XPS and FTIR analyses suggest that the doped N in the HTC carbon play an important role on the formation of extra pores during the activation. Furthermore, the activated N-doped microsphere carbon delivers the highest specific capacity (349 F g(-1)) at a current density of 1 A g(-1) in 6 mol L-1 KOH. Our findings promise an efficient route to the preparation of N-doped highly porous carbon with high capacitive performance.