Synthesis of mesopore-dominated porous carbon with ultra-high surface area via urea-assisted KOH activation

A mesoporous porous carbon (PC-KOH + Urea) with ultra-high specific surface area (SSA) was prepared from steam exploded poplar through urea-assisted KOH activation. The obtained PC-KOH + Urea had an ultra-high SSA of 3316 m(2) g(-1) and a total pore volume (V-T) of 1.96 cm(3) g(-1), much higher than that of PC-KOH and PC-Urea, produced by KOH and urea activation alone, respectively. Meanwhile, PC-KOH + Urea possessed extremely high mesopores surface area (S-meso) (2183 m(2) g(-1)) and mesopore volume (V-meso) (1.46 cm(3) g(-1)). In addition, urea can also serve as nitrogen source to dope nitrogen into PC-KOH + Urea, resulting in nitrogen content of 3.29%. To study the effects of urea on pore-forming, thermogravimetric analysis (TG) and thermogravimetric infrared technology (TG-IR) were adopted. It can be assumed that the ultra-high SSA of PC-KOH + Urea was mainly attributed to the reactions between pyrolysis products of urea and carbon. With ultra-high SSA, mesopore-dominated structure, and nitrogen doping, PC-KOH + Urea exhibited a high specific capacitance of 335.3 F g(-1) at current density of 0.5 A g(-1) in 6 M KOH aqueous electrolyte. In cyclic stability measurement, the capacitance retentions of PC-KOH + Urea were 99.6% after 4000 cycles. Thus, urea-assisted KOH activation was a feasible method to produce porous carbon with excellent performance.