Abstract
Freshwater scarcity is one of the most challenging issues facing mankind nowadays. Affected by the fast population growth and intensified industrialization, this challenge will persist or even become worse. Under such circumstances, desalination is considered as one of the most popular and promising methods of producing potable water. Yet with the conventional desalination technologies being pushed to their limits of capacity and cost, it is vital to develop sustainable desalination solution with low energy consumption. As an emerging desalination technology, capacitive deionization (CDI) has been experiencing rapid development in the last two decades. Relying on two porous carbon electrodes, the ions in high salinity solution can be attracted and immobilized in the electrical double layers of porous structure in the electrodes with an electrical potential. Compared with the traditional desalination methods such as distillation and reverse osmosis, CDI processes require less capital and operational cost. While due to the insufficient energy efficiency and adsorption capacity of the current CDI performance, the feasible large-scale CDI systems for industrial desalination applications are challenging to achieve. Therefore, this thesis is aimed to promote the desalination performance of CDI with novel electrode materials and design a low-cost desalination system using such nanomaterials to demonstrate the feasibility of CDI in practical industrial implementation. This thesis presents a series of nanomaterials developed for various types of CDI applications. Chapter 1 presents an overall review of the CDI technology. Chapter 2 to 4 focus on the porous carbon composites for salt adsorption via electrical doubly layers. Chapter 5 describes the metal oxide/carbon composites for pseudocapacitive adsorption. Chapter 6 introduces ion-intercalation materials as the electrodes of a dual-ion deionization system. Chapter 7 summarizes the development process of a multi-stage desalination system. Chapter 8 concludes achievements from this thesis and advises further research directions. The work and conclusion presented in this thesis can inspire the design of advanced CDI electrode materials and practical CDI devices as the alternative solutions to grand freshwater challenges.