Electrochemical Capture and Storage of CO2 as Calcium Carbonate

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.</p

Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis

The energetic convenience of electrolytic water splitting is limited by thermodynamics. Consequently, significant levels of hydrogen production can only be obtained with an electrical energy consumption exceeding 45 kWh kg(-1)H2. Electrochemical reforming allows the overcoming of such thermodynamic limitations by replacing oxygen evolution with the oxidation of biomass-derived alcohols. Here we show that the use of an original anode material consisting of palladium nanoparticles deposited on to a three-dimensional architecture of titania nanotubes allows electrical energy savings up to 26.5 kWh kg(-1)H2 as compared with proton electrolyte membrane water electrolysis. A net energy analysis shows that for bio-ethanol with energy return of the invested energy larger than 5.1 (for example, cellulose), the electrochemical reforming energy balance is advantageous over proton electrolyte membrane water electrolysis