Hybrid capacitive deionization with Ag coated carbon composite electrode

Abstract

Capacitive deionization (CDI) using capacitive electrodes is highlighted as an alternative desalination technology because of its advantages of low cost and high energy-efficiency. However, the deionization capacity of CDI is somewhat limited because its capacity relies on the double layer capacitance of a carbon electrode. Thus, improving the deionization capacity of a CDI system is one of the most urgent issues in CDI technology. Herein, Ag coated carbon composite electrode employed hybrid CDI system (Ag coated HCDI) was investigated to enhance the deionization performances. The Ag coated carbon composite electrode was made by coating a small amount of Ag onto a carbon capacitive electrode, exhibiting the characteristics of a battery and a capacitor together. As major results, the CDI deionization capacity (88% more), rate (39% more), and charge efficiency (76%➔92%) was dramatically enhanced due to the Ag coating. The significant improvement in deionization performance is explained by the enhanced specific capacity combining the capacitance in the carbon electrode with the Ag mediated charge transfer reaction. In addition, the Ag coated HCDI (73.3kJmole−1) is superior to membrane assisted CDI (136.7kJmole−1) in terms of energy consumption for deionization due to its low voltage feasible operation.