Integrated Electrochemically Assisted Absorbers for the Removal of Carbon Dioxide

Abstract

An integrated electrochemical device consisting of a two compartment 3-D printed resin electrochemical cell equipped with a 3-D printed titanium (3DP-Ti) cathode is designed, manufactured, and tested. This device aims to achieve simultaneous carbon dioxide fixation through electrochemically assisted reactive absorption, as well as the production of hydrogen and other reactions such as the formation of chlorine, depending on the composition of the anolyte. Gases with different percentages of carbon dioxide can be successfully processed. The fixation of carbon dioxide as bicarbonate is highly effective (reaching 33.75 mmol CO₂ (Ah)⁻¹ and 254.72 mg CO₂ (Wh)⁻¹), and it is based on the reaction of the hydroxyl ions produced during the discharge of water with the incoming carbon dioxide. Throughout the process, pH can be maintained in values close to neutrality, and the special design of the titanium GDE prevents scaling. Cell voltage is maintained during the long-term operation of the process, and its value depends on the catholyte and anolyte composition. Prevention of scaling becomes a major advantage associated to the use of 3DP-Ti as compared with the use of carbonaceous GDE. Performance does not significantly depend on the supporting catholyte used, and catholytes containing high concentrations of bicarbonates can be used efficiently, even when the concentration is higher than solubility. This opens the possibility for a combination with a separation stage of bicarbonates and the purification of this valuable byproduct. Coulombic efficiencies in the range 90-100 % can be obtained with the application of current densities within the range of 150 to 375 mA cm⁻². The system can operate successfully with gas retention times ranging from 0.3 to 2.4 seconds, and the quantity of bicarbonates produced depends linearly on the ratio current applied/flowrate of gas fed.