Thermodynamics of\nElectrochemical Marine Inorganic\nCarbon Removal

In recent years, marine carbon removal technologies have\ngained\nattention as a means of reducing greenhouse gas concentrations. One\nfamily of these technologies is electrochemical systems, which employ\nFaradaic reactions to drive alkalinity-swings and enable dissolved\ninorganic carbon (DIC) removal as gaseous CO<sub>2</sub> or as solid\nminerals. In this work, we develop a thermodynamic framework to estimate\nupper bounds on performance for Faradaic DIC removal systems. To assess\nthe fundamental mass balances of these systems, we first define unit\noperations in the DIC/total alkalinity (TA) space. By coupling a seawater\nspeciation model to an electrochemical framework, we provide a generalized\ncomparison of gas evolution and mineralization DIC removal routes,\nfocusing on asymmetric charge/discharge systems. We then show how\nthis framework can be extended to other processes, such as those employing\ndilution schemes. Finally, we provide a minimum energetic assessment\nof mCDR pathways relative to direct air capture. Overall, this thermodynamic\nframework aims to guide system and process design and to drive material\ndiscovery and engineering for future electrochemical marine DIC removal\nsystems.