Rational synthesis of microporous carbons for enhanced post-combustion CO 2 capture via non-hydroxide activation of air carbonised biomass.

This work explores the use of a less corrosive activating agent, potassium oxalate (PO), in combination with difficult to activate carbonaceous matter for the preparation of activated carbons. The design of the study allowed a fuller understanding of the workings of PO compared to hydroxide (KOH) activation, and also optimised the preparation of highly microporous carbons with exceptional CO 2 storage capacity under low pressure (≤1 bar) conditions at ambient temperature. The PO activated carbons have a surface area of up to 1760 m 2 g -1 and are highly microporous with virtually all of the surface area arising from micropores. The porosity of the PO activated carbons can be readily tailored towards having pores of size 6-8 Å, which are highly suited for CO 2 storage at low pressure ( i.e. , post-combustion capture). At 25 °C, the PO activated carbons can store up to 1.8 and 5.0 mmol g -1 of CO 2 at 0.15 bar and 1 bar, respectively. On the other hand, KOH activated carbons reach a higher surface area of up to 2700 m 2 g -1 , and store up to 1.0 and 4.0 mmol g -1 of CO 2 . This work demonstrates that PO may be used as a mild, less corrosive and less toxic activating agent for the rational and targeted synthesis of biomass-derived activated carbons with tailored porosity. The targeted synthesis may be aided by careful selection of the biomass starting material as guided by the O/C ratio of the biomass.