Production of highly microporous carbons with large CO₂ uptakes at atmospheric pressure by KOH activation of peanut shell char

Abstract

Highly microporous carbons with large CO₂ uptakes at atmospheric pressure were prepared by KOH activation of peanut shell char at different temperatures (680–780 °C). The porous carbons (PCs) showed a microporosity of 99.0–99.5 %, with micropore volume and specific surface area varying from 0.73 to 0.79 ml/g and 1713 to 1893 m²/g, respectively. The adsorption of CO₂ onto the PCs was a physisorption process. The CO₂ uptakes of the PCs increased with decreasing the activation temperature. The 680 °C-activated sample showed a 1-bar CO₂ uptake of 7.25 mmol/g (0 °C), which was among the highest values ever reported for biomass-based PCs. The high uptake was principally ascribable to its developed small micropores (<1 nm). Besides, this PC displayed a large 1-bar CO₂ uptake at 25 °C (4.41 mmol/g), fast CO₂ adsorption rate, moderate CO₂-over-N₂ selectivity, and excellent recyclability. These adsorption properties showed that the peanut-shell-based PC was a promising adsorbent for CO₂ capture or storage.