Zeolite-templated nanoporous carbon for high-performance supercapacitors

Hierarchical porous carbon prepared with calcium-containing nanocrystalline beta zeolite as the template and ethylene as the carbon source at a relatively low carbonization temperature (600 °C) displayed excellent electrocapacitive properties. The presence of both micro/mesopores and surface oxygen-containing groups on the ordered porous structure, along with a high specific surface area (2280 m² g^-1) and pore volume (1.95 cm³ g^-1) coupled with good wettability towards the electrolyte enabled the carbon to perform well as a supercapacitor electrode. This carbon electrode achieved a specific capacitance of 250 F g^-1 at a current density of 1 A g^-1 with 1 M H₂SO₄ as the aqueous electrolyte measured in a three-electrode system. A symmetric capacitor fabricated with the carbon as both electrodes exhibited a specific capacitance of 161 F g^-1 at a current density of 1 A g^-1, and an excellent cycling stability. After being cycled 17000 times and shelved for another two months, the electrode exhibited a specific capacitance of 246 F g^-1 at 1 A g^-1, 153% of the initial capacitance, and still maintained an excellent cycle stability. Besides, an all-solid-state supercapacitor cell fabricated with this carbon as both electrodes and polyvinyl alcohol/H₂SO₄ gel as the electrolyte displayed an areal specific capacitance of 413 mF cm^-2 at a current density of 0.25 mA cm^-2.