K2CO3 on porous supports for moisture‐swing CO2 capture from ambient air

Abstract Direct air capture (DAC) of CO 2 is an important technology to mitigate mobile carbon emissions, reduce atmospheric CO 2 concentration, and cope with climate change. Moisture‐swing adsorption is regarded as one of the most promising technologies in DAC due to its low energy consumption and ease of operation. In this work, a cheap and easily available moisture‐swing adsorbent of potassium carbonate loaded on porous supports (i.e., activated carbon, magnesium oxide, and zeolite) was prepared for CO 2 capture from ambient air. The composite adsorbent of potassium carbonate on activated carbon showed the best performance with a DAC capacity of 0.562 mmol/g at 25°C and 5% relative humidity. The effects of temperature, relative humidity, and CO 2 concentration on the adsorption performance were investigated systematically, as well as the cyclic DAC performance. In 50 adsorption–desorption cycles, the adsorption capacity of the composite adsorbent decreased by ~40% due to potassium carbonate leaching loss during water evaporation but can be fully recovered simply by re‐impregnating with potassium carbonate again.