One step N-doping and activation of biomass carbon at low temperature through NaNH2: An effective approach to CO2 adsorbents

This study offers a simple, environmentally friendly, and low-cost method to prepare N-doped adsorbents with outstanding CO 2 adsorption property under 1 bar. Utilizing waste walnut shell as adsorbents precursor and NaNH 2 as chemical activator and nitrogen source, porous adsorbents containing nitrogen are prepared at low temperature zone 400–500 °C. Also, by adjusting the activation temperature of the adsorbent and the ratio of NaNH 2 /AC, the pore structure and nitrogen content of the adsorbent are regulated to affect CO 2 adsorption performance. The specific surface area of the prepared series of nitrogen-containing porous adsorbents is from70 m 2 /g to 419–1721 m 2 /g. The result indicates that the optimal adsorbent has the highest 5.22 mmol/g of CO 2 adsorption capacity. A systematic study on the prepared series of adsorbents demonstrates that the narrow pore volume, pore structure and nitrogen content of the adsorbent jointly affected adsorption performance of CO 2 . Besides, these walnut shell-derived N-doped adsorbents show appropriate CO 2 /N 2 selectivity and Q st . The numerous advantages of the cheap waste walnut shell adsorbents enjoy simple and low-temperature synthesis process indicating that they are outstanding substitution to CO 2 adsorbents. The study hopes to further understand the synthesis of N-doped carbon and its carbon dioxide adsorption mechanism.