Electrochemical CO2 capture thermodynamics

•Thermodynamic cycles for electrochemical CO2 capture dominated by state of charge.•Energetics depend on system architecture and configuration.•Electrochemical CO2 capture can be favorable energetically. We analyze four general architectures for electrochemically mediated carbon dioxide capture systems, in each of which the electrophilicity of a redox active absorbent or absorbent blocking species is manipulated to influence the system's affinity for CO2. It is shown that the open circuit potentials of these architectures converge given the appropriate reference - namely a state in which no CO2 is present in the stream. The resulting difference between the open circuit potential of a stream and of that same stream lacking CO2 is referred to as the deviation potential. In the context of this deviation potential, four system process configurations are analyzed. The most efficient process configuration for all four electrochemical architectures is one that employs both a cathodic absorption taking place simultaneously with the reduction process and an anodic desorption that occurs along with the oxidation of the redox active species; decoupled electrochemical reactions and absorption/desorption steps incur significant energetic penalties.