Activated Carbon Fiber Felt Composites for the Direct Air Capture of Carbon Dioxide

Negative emissions technologies to mitigate climate change require innovative solutions for the direct air capture (DAC) of CO 2 from the atmosphere. K 2 CO 3 readily reacts with CO 2 to form KHCO 3 ; however, bulk K 2 CO 3 suffers from very slow sorption kinetics. By incorporating K 2 CO 3 into activated carbon (AC) fiber felts, the sorption kinetics were significantly improved by increasing the surface area of K 2 CO 3 in contact with air. The AC‐K 2 CO 3 fiber composite felts are flexible, cheap, easy to manufacture, chemically stable, and show excellent DAC capacity and (de)sorption rates, with stable performance up to ten cycles. Cyclic testing was demonstrated with 4 h sorption and 0.5 h desorption intervals. The best composite felts collected an average of 478 μmol of CO 2 per gram of composite during 4 h of exposure to ambient air (19 % relative humidity) that had a CO 2 concentration of 400–450 ppm after regeneration at 125 °C in an air furnace. An increase in the dew point temperature from 0 to 12 °C decreased sorption performance of the composite felts by 40 %.