Abstract
Capacitive deionization is a water desalination technology in which ions are stored in electrodes in an electrochemical cell construction, connected to an external circuit, to remove ions present in water from various sources. Conventionally, carbon has been the choice of material for the electrodes due to its low cost, low contact resistance and high specific surface area, electronic conductivity, and ion mobility within pores. The ions in the water are stored at the pore walls of these electrodes in an electrical double layer. However, alternative electrode materials, with a different mechanism for ion and charge storage, referred to as ion intercalation, have been fabricated and studied as well. The salt adsorption performance exhibited by these materials is in most cases higher than that of carbon electrodes. This work traces the evolution of the study of redox activity in these intercalation materials and provides a chronological description of major developments in the field of Capacitive Deionization (CDI) with intercalation electrodes. In addition, some insights into the cell architecture and operation parameters are provided and we present our outlook of future developments in the field of intercalation materials for CDI.
Highlights
The electrochemical technology of Capacitive Deionization (CDI) has witnessed an exponential increase in research and development efforts over the past years
⇒ Keywords: (2) This study demonstrated for the first time the electronic activity and redox properties of Prussian blue (PB)
Energy values for the desalination battery and reverse osmosis were compared and it was found that the energy required for 25% reduction in salt concentration was 0.3 Wh/L, a value that, according to the authors, is comparable to that obtained for reverse-osmosis under similar conditions (0.2 Wh/L)
Summary
The electrochemical technology of Capacitive Deionization (CDI) has witnessed an exponential increase in research and development efforts over the past years. If an electrode is perfectly selective to only adsorb either cations or anions, the ion storage capacity is directly proportional to the capacity to store charge, expressed in mAh/g The utilization of this capacity depends on many factors, primary among them are the current density (in a constant current experiment [26]) and voltage (in a constant voltage experiment) and the salt concentration of the water. An ideal CDI cell should have sufficient salt adsorption capacity, a high salt removal rate and low energy input Our work is intended to help in consolidating the efforts of the CDI community towards achieving improved solutions to selective and energy-efficient water desalination
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