Separation Of Co2 From Dilute Gas Streams Using A Membrane Electrochemical Cell

We report on an electrochemically driven CO2 separation process employing commercial anion exchange membranes to directly remove CO2 from a dilute gas mixture and transport it across a cell. This methodology exploits the carbonation behavior of alkaline membrane systems to react CO2 with hydroxide ions generated through the hydrogen evolution reaction and form (bi)carbonate ions. Electrochemically pumped (bi)carbonate then evolves as CO2 on the anode side through the hydrogen oxidation reaction with H-2. The resulting mixture of CO2 and residual H-2 could be utilized for downstream valorization processes. Cell polarizations with 0.1-100% CO2 in N-2 as the feed gas were performed with current densities of up to 50 mA.cm(-2), and CO2 concentrations were monitored using online gas analysis. Further experiments examining the effect of pumping against pressure and concentration gradients were performed, along with Pd wire reference electrode experiments to discern cathode and anode overpotentials. Additional fundamental techno-economic considerations are presented to explore the cost dynamics of the system and the relevant targets for cell operation. The results show the complex interactions between cell input and performance parameters, as well as some of the critical limitations that must be overcome to allow for process scale-up to become viable.