The synergistic effect of oxygen-containing functional groups on CO2 adsorption by the glucose–potassium citrate-derived activated carbon

Abstract

A high surface area activated carbon prepared by an innovative approach using glucose as a carbon source and neutral potassium citrate (PC) as an activator was compared with the porous carbon from glucose using corrosive potassium hydroxide (KOH) as an activator. The PC method showed two notable advantages over KOH activation. The PC method not only significantly increased the yield of the activated carbon, particularly at high carbonization temperatures without sacrificing porosity, but also enhanced the oxygen content in the activated carbon. After investigating CO₂ adsorption on these activated carbons, a remarkable uptake of 3.57 mmol g⁻¹ at 25 °C at 1 bar was observed by the glucose–PC-derived carbon sample, which possessed the highest oxygen content. In addition, the glucose–PC-derived carbon samples exhibited higher CO₂/N₂ selectivity than the glucose–KOH derived samples. Coupled with the density functional theory (DFT) analysis that focused on the binding energy calculation, the doped oxygen-containing functional groups, such as carboxyl and hydroxyl groups, could effectively enhance the adsorption of CO₂.