Phosphorus and Nitrogen Codoped Porous Carbon Nanosheets for Energy Storage and Gas Adsorption

Heteroatom-doped porous carbon has emerged as a promising candidate for capacitive energy and gas storage applications because of its abundant availability and cost-effectiveness. In this study, a solvothermal strategy was adopted to synthesize phosphorus (P) and nitrogen (N) codoped activated carbon (PCN-x) with an abundance of micropores, which can be utilized in both energy storage and gas (such as H2 and CO2) adsorption applications. The optimized P and N codoped porous carbon activated at 800 °C (PCN-800) shows a very high specific capacitance (Cs) of 575.15 F g–1 in an acid medium, and the Cs value was calculated to be 477.63 F g–1 under a 1 A g–1 current in an alkaline medium. The symmetric device performance shows an excellent energy density of 10.61 W h kg–1 at a power density of 250 W kg–1 along with a capacitance retention of 91.23% up to 10,000 cycles in an alkaline medium. The P and N codoped porous carbon activated at 900 °C (PCN-900) shows a high specific surface area (SSA) of 2953.2 m2 g–1 with a high micropore volume of 0.77 cc g–1. It also shows a good H2 storage capacity of 3.26 wt % at 77 K and 1 bar pressure. The CO2 adsorption capacities were calculated to be 5.98 mmol g–1 at 0 °C and 3.61 mmol g–1 at 25 °C with good selectivity of CO2/N2 and CO2/CH4. The incorporation of P and N codoped species into porous carbon nanosheets presents a promising avenue for improving the performance of energy and gas storage applications. The synergistic effects of P and N doping and the porous morphology and high SSA contribute to the improved electrochemical performance, enabling higher energy and power densities in supercapacitor devices along with good H2 and CO2 uptake capacities.