An all-in-one material with excellent electrical double-layer capacitance and pseudocapacitance performances for supercapacitor

•The all-in-one materials (3D PNGs) were prepared through a simple annealing method.•NH3 released from urea acted as pore generator and nitrogen source.•The PNGs300-800 exhibits large BET surface area (490.2 m2 g−1).•The PNGs300-800 shows promising capacitive performance and energy density (19.9 W h kg−1).