Recent advanced freestanding pseudocapacitive electrodes for efficient capacitive deionization

The development of advanced freestanding pseudocapacitive electrode materials with controlled topography, structural complexity, and improved desalination performance has garnered significant interest in recent years, particularly as water scarcity becomes increasingly prevalent. In this paper, we present a comprehensive review of recent advancements in the rational design of freestanding electrodes for hybrid capacitive deionization (CDI) to enhance their desalination capacity, stability, and selectivity. The review begins by summarizing advanced electrode materials that have been fabricated using different methods to boost CDI performance. Various novel synthetic strategies are discussed, highlighting their effectiveness in improving electrode capacitance, increasing active site density, and optimizing pore structure. The focus then shifts to categorizing electrode materials into low-dimensional and 3D hierarchical porous structures to boost their electrochemical and CDI properties. Furthermore, the review discusses the applicability of CDI in versatile industrial processes, including heavy metal removal, resource recovery, water softening, and water disinfection. The potential of CDI in these applications is promising, and further research is needed to optimize the design of freestanding electrodes for these specific purposes. Finally, the review concludes with a summary and outlook, providing comments on current scientific and technical challenges and future developments. With the advancement of advanced freestanding electrode materials, it is anticipated that this review will shed light on the emerging field of hybrid CDI in environmental research and stimulate further research in this area.