Preparation and formation mechanism of porous carbon nanosheets by thermal decomposition of polyvinyl alcohol films impregnated with zinc (II) and nitrate ions

Abstract

Porous carbon nanosheets (PCNS) with high surface areas were prepared by thermal decomposition of polyvinyl alcohol (PVA) films impregnated with Zn2+ and NO3−. Through this simple preparation method that required no additional activation processes, curved carbon nanosheets (<30 nm thick) were assembled into novel carbon materials. Detailed thermogravimetry–differential thermal analyses of the PVA films impregnated with Zn2+ and NO3− indicated that the sheet-like structures originated from exothermic pyrolysis of NO3− associated with the thermal decomposition of PVA. According to the nitrogen adsorption isotherm analyses at 77 K, the PCNS had a high specific surface area (>1600 m2 g-1) and bimodal pore structure consisting of micropores and mesopores. Because of their unique structural properties, the PCNS are attractive for use as electrode materials. The electrode performance of the PCNS was investigated in 1-M tetraethylammonium tetrafluoroborate ((C2H5)4NBF4) in propylene carbonate. The PCNS electrodes displayed high specific capacitance (86 F g-1 for cations and 115 F g-1 for anions). They also showed exceptionally high rate performance with ∼90% capacitance retention at current densities up to 2 A g-1 because their nanosheet structure allowed the rapid diffusion of ions inside the electrode.