N-doping and ultramicroporosity-controlled crab shell derived carbons for enhanced CO2 and CH4 sorption

Highly N-doped crab shell-derived carbon nanofibers (CSCNs) with enhanced sorption capacity for CO2 and CH4 are presented. Two different carbonization temperatures, 600 degrees C and 900 degrees C were utilized to control the N-doping level of the CSCNs; the N-content of CSCN processed at 600 degrees C is higher than that processed at 900 degrees C. After judicious activation process to fine-tune ultramicroporosity ( < 1 nm) by hot CO2 treatment, the CSCN obtained from 600 degrees C with the most developed ultramicroporosity showed higher CO2 uptake capacity compared to that of CSCN carbonized at 900 degrees C due to higher N-doping level, although the ultramicroporosity of the two samples is similar. In contrast, similar CH4 sorption capacities were identified for these samples. In addition, very efficient and selective separation of CO2/N-2 was achieved from CSCN carbonized at 600 degrees C with maximum ultramicroporosity; meanwhile, similar selective separations of CH4/N-2 were observed for both of the most activated CSCNs. As a result, the relationship between the ultramicroporosity and CO2 and CH4 uptake capacities, and N-doping effect are clearly elucidated.