Three-dimensional nitrogen and oxygen co-doped hierarchical porous carbons prepared from polyacrylonitrile/polyamic acid composite films for supercapacitors

Porous carbon materials are widely used in energy storage, adsorption, catalysis, and wastewater treatment. Polymer composite films of polyacrylonitrile (PAN) and polyamic acid (PAA) were firstly prepared by phase separation with modulation of coagulation bath composition. Using these composite films as precursors, nitrogen and oxygen co-doped porous carbon materials were successfully fabricated by preoxidation, carbonization, and subsequent NaOH activation. The porous carbons had a three-dimensional interconnected structure with a specific surface area of 450-737 m2 g-1. The pore volume was 0.245-0.508 m3 g-1 and the pore size mainly located between 1 and 5 nm. The activated porous carbon obtained from PAN/PAA coagulated at a DMSO to water ratio of 3 showed a high oxygen content of 28.0 wt% and nitrogen content of 3.3 wt%. The resultant porous carbon exhibited a good mass-specific capacitance of 407.7 F g-1 at a current density of 0.5 A g-1, an excellent rate capability (237.7 F g-1 at 20 A g-1) and cyclic stability. Using the material as the electrode, a coin-cell symmetric supercapacitor (CR2032) was assembled, which provided a specific capacitance of 156 F g-1 at 0.1 A g-1 and a maximum energy density of 10.9 Wh kg-1 at a power density of 50 W kg-1. The high number of heteroatoms as well as the textural properties could be beneficial for the improvement of electrochemical per-formance of the carbon-based supercapacitors.