CO2 regenerative battery for energy harvesting from ammonia-based post-combustion CO2 capture

Amine-based CO2 capture is considered the most mature technology for industrial application in coal-fired power stations, but its large energy requirement represents a major barrier to commercial deployment. Here, we introduce a novel approach involving a CO2 regenerative amine-based battery (CRAB), which harvests the chemical energy from amine-based CO2 capture through a metal-mediated electrochemical process. The CRAB process uses the dual ability of amines (i.e. ammonia) to reversibly react with CO2 and complex with metal ions (i.e. copper) to convert the CO2 reaction enthalpy into electrical energy. To determine how the CRAB process harvests energy from CO2 capture, we established a validated chemical model for CRAB system which was used to predict the electrode potentials, and conceive a CRAB cycle that links CO2 absorption/desorption with the electrochemical process. Modelling results indicate that CRAB could at best produce 8.4 kJe/mol CO2 from a copper/ammonia based energy harvesting system, while optimised CRAB experimentally discharged 6.5 kJe/mol CO2 of electrical energy with a maximum power density of 32 W/m2. When CRAB is coupled with an advanced ammonia process, the experimentally achieved energy output could reduce capture energy requirement to 0.177 MW h/tonne CO2 (including CO2 compression to 150 bar), with a high thermodynamic efficiency of CO2 capture of 62.1% (relative to thermodynamic minimum work of 0.11 MW h/tonne CO2). Our results demonstrate the technical feasibility of the CRAB system to harvest electrical energy from CO2 capture process, providing a pathway to significantly reduce capture energy requirement.