DESIGN AND SYNTHESIS OF HIERARCHICAL POROUS CARBONS FOR OPTIMUM PERFORMANCE OF CAPACITIVE DEIONIZATION ELECTRODE

Capacitive deionization, CDI has emerged as a promising alternative that competes with other existing desalination techniques. Typically, carbon is used as the active material for the CDI electrodes and is considered to be at the heart of this application. Understanding the role of the design parameters of porous carbon on the electrosorption is especially important to maximize the capacitive deionization electrode performance. Amongst different types of carbon structures, hierarchical porous carbons HPCs have been proposed as promising materials for capacitive deionization electrodes due to their excellent electrosorption performance. However, the typically low mesopore fraction and broad pore size distribution limits their utilization in correlating between the pore matrices and the CDI performance. In this work we report the capacitive deionization performance of a series of HPCs synthesized via ice templation with a high fraction of mesopores and tight control over the amount and the size of mesopores. To assure close probing and accurate investigations of the relationship between the pore matrices and the electrosorption performance, the synthesized porous carbons were categorized into two categories; category I include predominantly meso-macro porous carbons and category II include combination of multilevel of porosities (micro-meso-macro) porous carbons. For the category I, the aim is to investigate how tuning the mesopore size, mesopore volume and the BET surface area affect the final performance of meso-macro porous carbons. While for category II, the aim is to understand how different mesopore structure behave as capacitive deionization electrode after the introduction of micropores. Besides the high salt capacity and fast removal rates that can be obtained by the synthesized HPCs, we believe that the adapted approach can offer a new platform to delineate the impact of specific mesopore (pore size and volume) as part of a hierarchical structure on the electrosorption behavior. The outcomes of this study (i.e. the existing correlations, broad trends, synergetic effects of micro-meso structure) can potentially be applicable to other types of carbons especially; mesopores carbons and micro-meso pore carbons. Accordingly, this understanding of the role of some of the design parameter of porous carbons can guide and provides a roadmap for further investigation, better design and development of porous carbons, and ultimately pave the way for practical applications of capacitive deionization