Porous carbons derived from Arecanut seeds by direct pyrolysis for efficient CO2 capture

In this report, we demonstrate the preparation of a series of carbon nanospheres (CNSs) with high surface area and tunable sizes from natural bioresource, Arecanut kernels, by using direct pyrolysis. This method offers a convenient approach to induce porosity in the synthesized carbons without the need for an activating agent. The textural parameters including the specific surface area, pore volume, and pore size can be controlled by the simple adjustment of the carbonization temperature from 700 to 1000°C. The CNSs prepared at 700°C showed a low specific surface area, whereas the higher carbonization temperatures (800–1000°C) supported the rise in specific surface area of the products (433.6–1001.4 m2/g). The carbon, hydrogen, and nitrogen (CHN) analysis revealed that the CNSs exhibited a high purity with the carbon percentage ranging between 96 and 99%. The synthesized materials were tested as adsorbents for CO2 gas, and it was found that the CNSs with the highest specific surface area of 1001.4 m2/g registered the CO2 adsorption capacity of 14.1 mmol/g at 0°C and 30 bar, which is a reasonably high value among reported porous carbons prepared without activation. This value of CO2 adsorption also stands above the activated carbon and multiwalled carbon nanotubes. The excellent CO2 adsorption capability of these adsorbents along with their low-cost synthesis offers a feasible pathway for designing such materials for other applications as well.