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

Abstract

This study offers a simple, environmentally friendly, and low-cost method to prepare N-doped adsorbents with outstanding CO2 adsorption property under 1 bar. Utilizing waste walnut shell as adsorbents precursor and NaNH2 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 NaNH2/AC, the pore structure and nitrogen content of the adsorbent are regulated to affect CO2 adsorption performance. The specific surface area of the prepared series of nitrogen-containing porous adsorbents is from70 m2/g to 419–1721 m2/g. The result indicates that the optimal adsorbent has the highest 5.22 mmol/g of CO2 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 CO2. Besides, these walnut shell-derived N-doped adsorbents show appropriate CO2/N2 selectivity and Qst. The numerous advantages of the cheap waste walnut shell adsorbents enjoy simple and low-temperature synthesis process indicating that they are outstanding substitution to CO2 adsorbents. The study hopes to further understand the synthesis of N-doped carbon and its carbon dioxide adsorption mechanism.