Direct air capture (DAC) technology removes CO2, the main greenhouse gas directly from the atmosphere, thus DAC is a useful tool for achieving net-zero and eventual net-negative carbon emissions. Although significant progress has been made over the past decades, DAC technology has not reached large scale commercialization yet. One of the major challenges in scale-up is the low concentration of CO2 in the air (around 400 ppm) and thus a low driving force for CO2 separation process. To provide insights into the technology scale-up, DAC studies often simulate air by using nitrogen and carbon dioxide gas mixtures. Here we demonstrate that, this assumption might significantly overestimate the absorption capacity of different solvents by not accounting for the high amount of O2 (21%) in air. CO2 have a higher solubility in aqueous solvents while O2 have a significantly higher partial pressure ≈525 times that of CO2. This study provides a systematic framework for DAC solvent optimization and offers new perspectives for design of the next generation carbon capture technologies. Our findings help to ensure that the testing of laboratory DAC systems is performed under representative conditions, helping avoid overestimation of the potential of the industrial carbon capture facilities when evaluating its commercial viability.
