Electrochemically Mediated Separation of Carbon Monoxide Using a Ni-Based Redox Couple

Carbon monoxide in industrial waste gases is often burned and is responsible for about 8% of industrial CO 2 emissions. In contrast to CO 2 capture, no conventional technologies are available for separating CO from nitrogen at scale. Here, we show that the difference in the CO binding affinity between [Ni I (cyclam)] + and [Ni II (cyclam)] 2+ can be leveraged in an electrochemical separation method: cycled capture and release of CO through potential control. The carrier, [Ni I (cyclam)] +, has a binding constant with CO that was estimated to be 7 × 10 3 M –1 through the deconvolution of cyclic voltammetry curves. An electroswing between −1.7 V and −1.5 V vs ferrocene is sufficient to switch between the capture and release of CO. A more positive release potential can increase the release rate of CO albeit at the expense of the current efficiency. This work shows that a [Ni(cyclam)]Cl 2 carrier can selectively separate and concentrate CO from nitrogen electrochemically.