Electrochemical CO2 capture with pH-independent redox chemistry
Abstract
Capture of anthropogenic CO2 is critical for mitigating climate change, and reducing the energy cost is essential for wide-scale deployment. Solubility of inorganic carbon in aqueous solutions depends on the pH, and electrochemical modulation of the pH has been investigated as a means of CO2 capture and release. However, reported methods incur unavoidable energy costs due to thermodynamic penalties. In this study, we introduce a pH-independent redox chemistry that greatly lowers the thermodynamic energy costs by changing the pH without directly changing the [H+]. We show that the redox reaction of TEMPO molecules modulates the pH for capture and release of CO2 in a flow cell with an energy cost as low as 2.6 kJ/mol of CO2 corresponding to 0.027 eV/molecule. A molecular model, supported by MD and DFT simulations, is proposed of how the pH is decreased by 7.6 while largely avoiding the entropic energy cost associated with increasing the [H+]. We believe that this work showcases the potential of pH-independent redox chemistries for practical and cost-effective CO2 capture.
Cite
@article{arxiv.2502.01028,
title = {Electrochemical CO2 capture with pH-independent redox chemistry},
author = {Sang Cheol Kim and Marco Gigantino and John Holoubek and Jesse E. Matthews and Junjie Chen and Yaereen Dho and Thomas F. Jaramillo and Yi Cui and Arun Majumdar and Yan-Kai Tzeng and Steven Chu},
journal= {arXiv preprint arXiv:2502.01028},
year = {2025}
}