MXene-based composites for capacitive deionization – The advantages, progress, and their role in desalination - A review

MXenes, a novel large family of 2D transition metal carbides, carbonitrides and nitrides are currently a "hot topic" in science due to their several fascinating physical and chemical properties. It follows from a rich diversity of their elemental compositions and chemical functionalities. MXenes can form composites with many substances, including polymers or metal oxides, which allows to effective "tune" MXene characteristics to a fit-to-the-purpose applications. Capacitive deionization (CDI) is currently widely studied as advanced desalination technique due to the advantages of cost-effectiveness, eco-friendly, and high salt removal capacity. One of key fields for CDI development relates to the ion's intercalation materials as concept taken from the sodium ion batteries, which is used in CDI because of their excellent desalination capacity. These materials provide effective sodium ions removal from the brine based on intercalation mechanism as well as redox reactions. In this review, we timely review an up-to-date accomplishment in the advancement of distinct MXene-based composite materials used as CDI electrodes, along with discussion of fundamental electrochemical energy storage mechanisms. The most relevant outcomes are highlighted together with the phenomena observed when applied in desalination applications. Finally, potential solutions as well as challenges in this field are summarized.