Surface Electrochemistry of Carbon Electrodes and Faradaic Reactions in Capacitive Deionization

• Published in: Environmental science & technology Vol. 56; no. 17; pp. 12602 - 12612
• Main Authors: Kang, Jin Soo, Kim, Seoni, Kang, Jiho, Joo, Hwajoo, Jang, Junghwan, Jo, Kyusik, Park, Subin, Kim, Hyoung-il, Yoo, Sung Jong, Yoon, Jeyong, Sung, Yung-Eun, Hatton, T. Alan
• Format: Journal Article
• Language: English
• Published: Easton American Chemical Society 06.09.2022
• Subjects: Carbon; Chemical reactions; Deionization; Desalination; Electrochemical desalination; Electrochemistry; Electrodes; Energy efficiency; Saline water; Salts; Treatment and Resource Recovery; desalination; Faradaic reaction; electrochemistry; capacitive deionization; carbon
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.2c03913

Recent advances in electrochemical desalination techniques have paved way for utilization of saline water. In particular, capacitive deionization (CDI) enables removal of salts with high energy efficiency and economic feasibility, while its applicability has been challenged by degradation of carbon electrodes in long-term operations. Herein, we report a thorough investigation on the surface electrochemistry of carbon electrodes and Faradaic reactions that are responsible for stability issues of CDI systems. By using bare and membrane CDI (MCDI) as model systems, we identified various electrochemical reactions of carbon electrodes with water or oxygen, with thermodynamics and kinetics governed by the electrode potential and pH. As a result, a complete overview of the Faradaic reactions taking place in CDI was constructed by tracing the physicochemical changes occurring in CDI and MCDI systems.