CO2 Separation Using Electrochemical Hydrogen Pumping

Abstract

IntroductionCarbon dioxide (CO2) separation and capture technologies are necessary for a decarbonized society. The chemical absorption method using an amine solvent has been demonstrated in steel and power industry. However, the separation process has some drawbacks such as material corrosion. In this study, we examined CO2 separation by electrochemical approach using hydrogen pumping.ExperimentalThe JARI fuel standard cell was employed and modified. It was divided in anode and cathode compartment by a cation exchange membrane. KHCO3 solution and KCl solution were circulated in the anode and cathode compartment, respectively. H2 gas was supplied to the anode at a constant flow rate by mass flow controller. Electrolysis was carried out at various cell voltages using a DC power supply unit. The gas from the anode was introduced into a quadrupole mass spectrometer (QMS). The volume rate of CO2 gas was measured by a mass flow meter.Results and discussionFigure 1 shows the current-voltage curve when H2 gas was supplied, and constant voltage electrolysis was carried out. The current was detected below the theoretical decomposition voltage of water (1.23 V). This supported that the reversible reaction of hydrogen pumping (H2 ⇆ 2H+ + 2e-) was occurred as expected. The Pt catalyst was contributed to the small overvoltage.During electrolysis, gas was generated in the anode solution. It was separated by a gas-liquid separator, and then introduced to QMS. Figure 2 shows the relationship between the ratio of CO2 gas and cell voltage. In our experiment, the CO2 purity was over 90% at all voltages. This suggested that water electrolysis with O2 evolution did not occur. That is, by controlling the cell voltage, the hydrogen pumping reaction take place preferentially, and H+ is effectively supplied to the anode compartment. This archive high CO2 gas separation. In poster session, results on energy consumption will also be presented. Figure 1