Electrolyte effects on the stability and CO binding of copper chloride complexes for electrochemical separation of CO/N2

Abstract

Carbon monoxide separation from industrial waste gases could contribute largely to carbon circularity. Traditional separation technologies are unable to separate CO from N2 selectively. Instead, electroactive carriers show promise in selective separation of CO from N2, where CO binds a complex in one oxidation state and releases in another oxidation state. We study Cu(I)/Cu(II)-chloride complexes as potential carrier materials with high binding affinity to CO, good solubility and low energy consumption of the process. We show that the electrolyte composition of a copper chloride system affects the binding affinity and stability of the copper carrier (Cu+). Cyclic voltammetry measurements reveal that the CO binding constant increase from the previously reported 1600 M-1 for 1 M KCl to 5500 M-1 for 0.5 M CaCl2. However, this increase in binding constant is not reflected to the same extent in the CO capture capacity, showing a smaller increase in CO capture. In general, the binding constant decreased with chloride concentration, while the Cu+ stability window increased. This highlights a trade-off that needs to be considered for electrolyte selection in electrochemical CO separation with copper chlorides.