Highly Porous Activated N‑Doped Carbon as an Ideal Electrode Material for Capacitive Energy Storage and Physisorption of H2, CO2, and CH4

Proper modulation of the compositions and porosities of carbon materials is crucial for capacitive energy storage and gas adsorption of carbon materials. Herein, porous N-doped carbon was synthesized from formamide by using a sequential hydrothermal treatment followed by pyrolysis with KOH. The activation with KOH resulted in a high increase in the porosity of the carbon and in the performance. A high porosity of >3000 m2 g–1 was achieved with a low KOH/C ratio of only 2. The presence of nitrogen introduces pseudocapacitance and also enhances the electron density in the carbon framework. The obtained N-doped porous carbon exhibits a good specific capacitance value of 307 F g–1 at 1 A g–1 in 6 M KOH. Also, the fabricated symmetric supercapacitor displays excellent performance in both alkaline and neutral media. It shows a stable cycling performance (91.4% retention after 10 000 cycles), a reasonable rate performance, and a maximum energy density of 14.36 Wh kg–1 at a power density of 351 W kg–1 in 1 M Na2SO4. The prepared material shows good gas adsorption behavior, and as a H2 adsorbent at 77 K, it shows a good uptake value of 2.86 wt % at 1 bar pressure. It also shows maximum CO2 uptake values of 4.88 and 2.88 mmol g–1 at 1 bar pressure under temperatures of 0 and 25 °C, respectively, with a high CO2/N2 selectivity of 14.54. The compound also shows a methane uptake capacity of 1.67 mmol g–1 at 0 °C and 1 bar pressure with a CO2/CH4 selectivity of 3.8. Our research provides a promising material for both energy storage and gas storage through a green synthetic strategy.