Abstract
The expanding global demand for fresh water necessitates the advancement of desalination technologies with massive production. While the state-of-art desalination techniques are pricey and energy consuming, thus are not optimal approaches to the water scarcity issue. Capacitive deionization (CDI) emerges as a promising desalination technique to address these challenges with expenditure and energy effectiveness. However, CDI is presently not suitable for industrial application due to its drawbacks of limited salt adsorption capacity and inapplicable to high saline solution. The recent adopted faradaic electrode materials are capable of addressing these two issues simultaneously, delivering superior energy efficiency and unprecedented desalination performance. This thesis elaborates the enhancement of CDI performance with rational design of electrode materials. Chapter 1 describes the current situation of water crisis and introduces the state-of-art desalination technologies, demonstrating the necessity in developing CDI as a sustainable desalination technology. Meanwhile, a detailed introduction to CDI including the adsorption theories, configurations, merits and most urgent challenges directs the way for subsequent studies. In chapter 2, Ar plasma treated MXene Ti3C2Tx is selected as a non-faradaic intercalation material for CDI. The surface modified MXene exhibits enhanced salt adsorption capacity and average salt adsorption rate. In chapter 3, a member of Prussian blue analogues is adopted as the anode material for CDI system. By introducing redox reaction into CDI system, the salt adsorption is not limited by the surface area of electrode materials as in traditional electrical double layer (EDL) based CDI, realizing superior salt removal characteristics with minimized energy consumption. Chapter 4 compares the CDI performance in the aspects of salt adsorption capacity, charge efficiency and energy consumption with capacitive and faradaic electrodes applied, explaining the necessity of developing faradaic electrode for advanced CDI systems. Based on the implications drawn from the previous chapters, a membrane-less desalination battery is fabricated with a bimetallic metal organic framework cathode in chapter 5, delivering unprecedented desalination efficiency. Our approach illuminants the way for future research of rational material design for CDI systems, providing evidence for the industrial applicability of CDI.