Enhancing Direct Air Capture through Potassium Carbonate Doping of Activated Carbons

Abstract Direct air capture of carbon dioxide (CO2) is one of the most promising strategies to mitigate rising atmospheric CO2 levels. Among various techniques, adsorption using porous materials is a viable method for extracting CO2 from air, even under humid conditions. However, identifying optimal adsorbent materials remains a significant challenge. Moreover, the performance of existing materials can be improved by doping with active species that boost gas capture, a relatively unexplored field. In this study, we perform atomistic simulations to investigate the adsorption, structural, and energetic properties of CO2 and water in realistic models of activated carbons. We first analyze the impact of explicitly considering surfaces containing functional groups, which aims to imitate the chemical environment of experimental samples. Additionally, we introduce potassium carbonate within the pores of the adsorbent to evaluate its effect on CO2 and water adsorption. Our results demonstrate that both functional groups and potassium carbonate enhance adsorption, primarily by shifting the adsorption onset pressures to lower values. Specifically, potassium carbonate clusters act as extra adsorption sites for CO2 and water, facilitating the nucleation of water molecules and promoting the formation of a hydrogen bond network within the activated carbon pores.