Electrowinning-coupled CO2 capture with energy-efficient absorbent regeneration: Towards practical application

Abstract Continuous drop of renewable electricity price offers excellent opportunity to electrify the CO2 capture processes in a cost-effective and decentralized way. Electrochemical CO2 capture represents a promising technology for CO2 emission reduction, particularly in the industries where thermal energy is not available. However, existing electrochemical technologies are either energy-intensive or operated at impractically low current densities. Here, we report an electrowinning-coupled CO2 capture (ECC) system which mimics industrially available electro-refining process for an energy-efficient amine-based CO2 capture. In applying ammonia as CO2 capture solvent and zinc metal as electrowinning medium, we experimentally achieved a low power consumption of 14.7 kJe/mol CO2 for solvent regeneration at an industrially preferred current density of 100 A/m2. This energy performance is very competitive with other state-of-the-art electrochemical CO2 capture technologies (50-500 kJe/mol CO2), and also outperforms the commercial amine processes driven by thermal energy (100-150 kJth/mol CO2). The desirable energy performance is due to the single-step two-electrons Zn(NH3)42+/Zn(s) redox reactions occurred during electrochemical operation of ECC, which avoids the formation of stable intermediate species and thus brings a low energy consumption. We anticipate the energy competitiveness would pave the way for ECC to move towards practical application.