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

Abstract 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 Na 2 SO 4 ) 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.