Development of Redox-Active Flow Electrodes for High-Performance Capacitive Deionization.

An innovative flow electrode comprising redox-active quinones to enhance the effectiveness of water desalination using flow-electrode capacitive deionization (FCDI) is described in this study. The results show that, in addition to carbon particle contact, the presence of the aqueous hydroquinone (H2 Q)/benzoquinone (Q) couple in a flowing suspension of carbon particles enhances charge transfer significantly as a result of reversible redox reactions of H2 Q/Q. Ion migration through the micropores of the flow electrodes was facilitated in particular with the desalination rate significantly enhanced. The cycling behavior of the quinoid mediators in the anode flow electrode demonstrated a relatively high stability at the low pH induced, suggesting that the mediator would be suitable for long-term operation.