High performance hybrid capacitive deionization with a Ag-coated activated carbon electrode

Abstract

Capacitive deionization (CDI) has been highlighted as a promising electrochemical water treatment system. However, the low deionization capacity of CDI electrodes has been a major limitation for its industrial application, and hence, there is a need for innovative electrode materials. In this study, we propose a high-performance hybrid CDI (HCDI) system by developing a Ag-coated activated carbon (AC) electrode. Ag particles were deposited on AC powder via a facile impregnation method. AC powders were dispersed in a AgNO₃ solution, followed by base treatment. The electrode prepared from the Ag-coated AC exhibited enhanced electrical capacity by the addition of Ag/AgCl electron transfer reaction. The HCDI system with Ag-coated AC showed a 43% higher deionization capacity than a conventional membrane CDI system. In addition, the deionization capacity of the HCDI system with Ag coated AC increased with the Ag loading on the AC. Moreover, the proposed HCDI system was capable of deionizing various cationic solutions (i.e., Na⁺, Mg²⁺, K⁺, Ca²⁺) demonstrating its potential to treat various sources of feed water (hard water, wastewater, etc.).