Sandwich-Type Microporous Carbon Nanosheets for Enhanced Supercapacitor Performance

Sandwich-type microporous hybrid carbon nanosheets (MHCN) consisting of graphene and microporous carbon layers are fabricated using graphene oxides as shape-directing agent and the in-situ formed poly(benzoxazineco-resol) as carbon precursor. The reaction and condensation can be readily completed within 45 min. The obtained MHCN has a high density of accessible micropores that reside in the porous carbon with controlled thickness (e.g., 17 nm), a high surface area of 1293 m(2) g(-1) and a narrow pore size distribution of ca. 0.8 nm. These features allow an easy access, a rapid diffusion and a high loading of charged ions, which outperform the diffusion rate in bulk carbon and are highly efficient for an increased double-layer capacitance. Meanwhile, the uniform graphene percolating in the interconnected MHCN forms the bulk conductive networks and their electrical conductivity can be up to 120 S m(-1) at the graphene percolation threshold of 2.0 wt.%. The best-practice two-electrode test demonstrates that the MHCN show a gravimetric capacitance of high up to 103 F g(-1) and a good energy density of ca. 22.4 Wh kg(-1) at a high current density of 5 A g(-1). These advanced properties ensure the MHCN a great promise as an electrode material for supercapacitors.