Electrochemical CO2 reduction and mineralisation in calcium containing electrolytes

One of the key challenges of room temperature aqueous CO2 electrolysis technology is the carbon losses because of carbonate formation. It is desirable if carbonate ions could be utilized concurrently for a useful process. Herein, we devise a strategy that enables in-situ electroreduction and assisted CO2 storage using a by-product of that reduction process and carbonate ions. By employing a Ag catalyst deposited on a gas diffusion layer, we demonstrate CO2 electroreduction and concurrent storage via mineralisation using seawater, as well as other calcium containing electrolytes. For example, CO2 electroreduction in 0.6 M Na2SO4 containing 400 ppm Ca electrolyte results in a Faradaic conversion efficiency to CO of ∼90 % at - 1.4 V vs. RHE (∼60 ± 6 mA cm−2), and concurrently stored CO2 as calcium carbonate. This bioinspired work offers a new avenue where CO2 storage is incorporated in a sustainable CO2 electroreduction technology.