Electrochemical Capture and Storage of CO2 as Calcium Carbonate

Abstract

A carbon dioxide capture, conversion, and utilization technology has been developed that can be powered by renewable energy with the potential to mitigate CO₂ emissions. This relies on an electrochemical process whereby the dissolution of carbon dioxide into carbonate ions is accelerated by a locally induced pH change at the cathode. The carbonate ions can then complex with metal cations, such as Ca²⁺ , Sr²⁺ , or Mn²⁺ , present in solution to form their respective metal carbonates, which precipitate out of solution. To ensure the cathode is not fouled by deposition of the insulating metal carbonate, the process is operated under hydrogen evolution conditions, thereby alleviating any significant attachment of the solid to the electrode. This process is demonstrated in CO₂ -saturated solutions while the possibility of direct air capture is also shown, where the precipitation of CaCO₃ from atmospherically dissolved CO₂ during electrolysis is observed. The latter process can be significantly enhanced by using 5 vol.% of monoethanolamine (MEA) in the electrochemical cell. Finally, the process is investigated using seawater, which is also successful after the initial precipitation of metal sulfates from solution. In particular, the use of renewable energy to capture CO₂ and create CaCO₃ while also generating hydrogen may be of particular interest to the cement industry, which has a significant CO₂ footprint.

Keywords: CO2 capture; crystallization; electrolysis; hydrogen evolution; metal carbonates.