Regulation of K 2 CO 3 Activation of Cotton Stalk-Based Nitrogen-Doped Porous Carbon and High-Efficiency CO 2 Adsorption Performance

Biomass porous carbon materials have broad application prospects in the field of CO2 capture due to their extremely high specific surface area and rich pore structure. However, the biomass precursors, due to their diverse components and complex microstructure, result in poor stability of the prepared porous carbon. Developing methods for preparing high-performance biomass porous carbon is of crucial importance. In this study, high-content plant fibers from cotton stalks were extracted through alkaline treatment and ultrasonic disruption. Biochar was prepared through high-temperature hydrothermal reaction, K2CO3 and urea were introduced as activation agents and nitrogen dopants for the biochar, respectively. After calcination at high temperatures, nitrogen-doped porous carbon materials were obtained. The results showed that the prepared materials had a high specific surface area of 1383 m2/g and formed a rich pore structure dominated by micropores. XPS analysis confirmed that nitrogen-doped materials successfully introduced nitrogen-containing basic functional groups, such as pyridine nitrogen on the surface, enhancing the Lewis acid–base interaction between the samples and CO2, and improving the CO2 adsorption performance. The adsorption capacity of NKCS-3 sample at 1 bar and 0 °C was 5.17 mmol/g, at 1 bar and 25 °C was 3.95 mmol/g. Moreover, this porous carbon exhibited excellent cyclic stability and good regeneration performance. After 50 adsorption and desorption cycles, its maximum adsorption capacity still remained above 95%. This study provides an effective and feasible implementation path for extracting high-content cellulose from biomass precursors to prepare high-performance biomass porous carbon.