Highly Capacitive, CNT-Rich, and N-Doped Carbon Skeleton Materials Derived from the Two-Step Pyrolysis of Humate-Ni-BTC/Melamine Precursor

A category of highly capacitive N-doped carbon skeleton material (NCS) containing abundant carbon nanotubes (CNTs) is synthesized by a two-step pyrolysis method using the flower-cluster-shaped humate-Ni-BTC (HA-Ni-BTC) template and melamine particles together as precursors. As the HA-Ni-BTC/melamine mass ratio is 1:3 and the pyrolysis temperature is 700 °C, the prepared optimal NCS-700 has plentiful CNTs and graphene layers; abundant mesopores possessing a mean pore diameter of 6.1 nm; a large surface area of 296.5 m2/g; applicable nitrogen doping forms mainly containing pyrrolic N, pyridinic N, and graphitic N; and an appropriate nitrogen doping dosage of 11.8 wt %. In the field of energy storage, the NCS-700 electrode appears to have a preferable charge-transfer resistance, internal resistance, and positive capacitance performances. In particular, the NCS-700 has an excellent specific capacitance of 357 F g–1 at 0.5 A g–1, high rate capability, and good cycle stationarity because of a capacitance residual of 94.5% at 5 A g–1 after 10 000 cycles. The assembled NCS-700//AC asymmetric supercapacitor also exhibits a desirable specific capacitance (123 F g–1 at 1 A g–1), good cycle stationarity (94.8% capacity after 10 000 cycles), and high specific energy (12.3 W h kg–1 even at 300 W kg–1). Hence, the obtained NCS is a promising highly capacitive and low-energy-loss electrode material for supercapacitors.