Highly Cost-Effective Nitrogen-Doped Porous Coconut Shell-Based CO₂ Sorbent Synthesized by Combining Ammoxidation with KOH Activation

Abstract

The objective of this research is to develop a cost-effective carbonaceous CO₂ sorbent. Highly nanoporous N-doped carbons were synthesized with coconut shell by combining ammoxidation with KOH activation. The resultant carbons have characteristics of highly developed porosities and large nitrogen loadings. The prepared carbons exhibit high CO₂ adsorption capacities of 3.44–4.26 and 4.77–6.52 mmol/g at 25 and 0 °C under atmospheric pressure, respectively. Specifically, the sample NC-650-1 prepared under very mild conditions (650 °C and KOH/precursor ratio of 1) shows the CO₂ uptake 4.26 mmol/g at 25 °C, which is among the best of the known nitrogen-doped porous carbons. The high CO₂ capture capacity of the sorbent can be attributed to its high microporosity and nitrogen content. In addition, the CO₂/N₂ selectivity of the sorbent is as high as 29, higher than that of many reported CO₂ sorbents. Finally, this N-doped carbon exhibits CO₂ heats of adsorption as high as 42 kJ/mol. The multiple advantages of these cost-effective coconut shell-based carbons demonstrate that they are excellent candidates for CO₂ capture