Role of micropores and nitrogen-containing groups in CO2 adsorption on indole-3-butyric acid potassium derived carbons

Abstract

Nitrogen-rich carbons for CO2 capture have received much attention in recent years, but the role of N-containing groups in CO2 adsorption has not been clearly elucidated. In this study, indole-3-butyric acid potassium (IBAP) as a new precursor was used to prepare the nitrogen-rich carbons via one-step carbonization. The IBAP-derived carbon prepared at 700°C exhibited high CO2 adsorption of 1.48mmol/g at 0.15bar and 4.53mmol/g at 1bar and 25°C, among the highly efficient activated carbons for CO2 adsorption. The high CO2 adsorption was attributed to not only the high volume of effective micropores, but also the effective N-containing groups on the IBAP-derived carbons. When carbonization temperatures increased from 500°C to 900°C, the nitrogen contents in the IBAP-derived carbons decreased from 6.35% to 0.70%. X-ray photoelectron spectroscopy (XPS) analysis confirmed that the pyrrolic-N in IBAP was converted into pyridinic-N, quaternary nitrogen and pyridinic-N-oxide in the carbonization process, and their contents first increased and then decreased with increasing carbonization temperatures. Only the pyrrolic-N was proved to be effective for CO2 adsorption on the IBAP-derived carbons, and its contribution to CO2 adsorption was pronounced for the carbons prepared at low temperatures. For the well-developed porous carbons, the effective micropores were mainly responsible for CO2 adsorption via micropore filling.