Improved capacitance of SBA-15 templated mesoporous carbons after modification with nitric acid oxidation

This study reports modified SBA-15 templated mesoporous carbon as a supercapacitor electrode for high-efficiency energy storage. Mesoporous carbon was oxidized in concentrated nitric acid at 26 °C, 50 °C, 70 °C and 100 °C. The evolution of mesopores and surface oxygen-containing functional groups (SOFGs) of the mesoporous carbons were studied by nitrogen cryosorption, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis. The results demonstrate that the specific surface area and the mesopore volume decrease, while the SOFGs accumulate with increasing oxidation temperature. The supercapacitor performance was characterized in a KOH aqueous electrolyte. An enhanced energy density with a highest value of 5.7 Wh/kg is obtained after oxidation at 100 °C compared to 3.5 Wh/kg before oxidation, demonstrating the possibility of using modified mesoporous carbons in high energy density applications. The enhanced energy density is attributed to the contribution of SOFGs to charge storage in both the electric double layer and the Faradic reaction. The power density is also improved with a highest value of 3125 W/kg after oxidation at 70 °C compared to the original value of 2015 W/kg. The improvement of power density relies on the improved wettability of carbon surfaces, which can facilitate the ion transport.