Urea-Modified Phenol-Formaldehyde Resins for the Template-Assisted Synthesis of Nitrogen-Doped Carbon Nanosheets as Electrode Material for Supercapacitors

Various kinds of phenol-formaldehyde resins modified with urea have been firstly designed and synthesized; next, nitrogen-doped carbon nanosheets with porous features are fabricated by a template-assisted carbonization method, using the resin as nitrogen and carbon sources, and commercial Mg(OH)(2) as template. Increasing the initial molar ratio of urea results in promoting porosity and N content. When a molar ratio of phenol and urea of 1:2 is employed, the resulting carbon nanosheets exhibit a large S-BET (1503 m(2) g(-1)), high pore volume (3.37 cm(3) g(-1)) and high N doping (6.44%). Moreover, the material delivers a remarkably improved capacitive performances with a high rate capability up to 81.27% (pristine material: 27.31%) and excellent cycling stability up to 119.1% (pristine material: 88.5%). Energy densities of up to 4.30 Wh kg(-1) (6.0 M KOH) and 10.42 Wh kg(-1) (1.0 M Na2SO4) are found, which are almost 2.70 and 6.61 fold compared to that of the pristine one. The present resin-based synthesis strategy can be extended to other systems and opens up an avenue for producing N-doped carbon materials for supercapacitor applications.