Development of Low-Cost Porous Carbons through Alkali Activation of Crop Waste for CO2 Capture

To achieve the “double carbon” (carbon peak and carbon neutrality) target, low-cost CO2 capture at large CO2 emission points is of great importance, during which the development of low-cost CO2 sorbents will play a key role. Here, we chose peanut shells (P) from crop waste as the raw material and KOH and K2CO3 as activators to prepare porous carbons by a simple one-step activation method. Interestingly, the porous carbon showed a good adsorption capacity of 2.41 mmol/g for 15% CO2 when the mass ratio of K2CO3 to P and the activation time were only 0.5 and 0.5 h, respectively, and the adsorption capacity remained at 98.76% after 10 adsorption–desorption cycle regenerations. The characterization results suggested that the activated peanut shell-based porous carbons were mainly microporous and partly mesoporous, and hydroxyl (O–H), ether (C–O), and pyrrolic nitrogen (N-5) functional groups that promoted CO2 adsorption were formed during activation. In conclusion, KOH- and K2CO3-activated P, especially K2CO3-activated P, showed good CO2 adsorption and regeneration performance. In addition, not only the use of a small amount of the activator but also the raw material of crop waste reduces the sorbent preparation costs and CO2 capture costs.