These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
submitted on 15.03.2019 and posted on 18.03.2019by Michael Aziz, David G. Kwabi
We propose and
perform a thermodynamic analysis of the energetic costs of CO2
separation from flue gas using a pH swing created by electrochemical
redox reactions involving
proton-coupled electron transfer from molecular species in aqueous
electrolyte. Electrochemical reduction of these molecules results in the
formation of alkaline solution, into which CO2 is absorbed;
subsequent electrochemical oxidation of the reduced molecules results in the
acidification of the solution, triggering the release of pure CO2
gas. We examined the effect of buffering from the CO2-carbonate
system on the solution pH during this pH swing cycle, and thus on the
open-circuit potential of a hypothetical electrochemical cell in a 4-step CO2
capture-release cycle. The thermodynamic minimum work input varies from 16 to
75 kJ/molCO2 as throughput increases, for both flue gas and direct
air capture, with the potential to go substantially lower if CO2
capture or release is performed simultaneously with electrochemical reduction
or oxidation. These values are compared with those for other separation methods. We discuss the properties
required of molecules that would be suitable for such a cycle.