Controlled fabrication of mesoporous electrodes with unprecedented stability for water capacitive deionization under harsh conditions in large size cells

• Published in: Desalination 2021-09, Vol.511, p.115099, Article 115099
• Main Authors: Taha, Manar M., Anwar, Soha E., Ramadan, Mohamed, Al-Bulqini, Hazem M., Abdallah, Muhammed S., Allam, Nageh K.
• Format: Article
• Language: English
• Subjects: Capacitive deionization; Electrosorption; Mesoporous carbon network; Nitrogen doping; Oxygen saturated feed cycling stability; Potential of zero charge
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/j.desal.2021.115099

Capacitive deionization (CDI) is a feasible low-cost desalination technique for low-to-medium (brackish) salinity water. However, cycling stability and regeneration of the CDI electrodes are the bottlenecks hindering the practical application of the technology on large scale. Oxidation of the electrodes during the sequential adsorption-desorption processes is one of the most challenging problems hindering their long-term cycling performance. Herein, we demonstrated the ability to design and fabricate exceptionally stable CDI electrodes via a one-pot pyrolysis protocol. The optimized pyrolysis of nitrogen‑carbon precursors at different temperatures enabled the fabrication of carbon materials with a controlled amount nitrogen dopant (NDCs) with exceptional cycling stability. The NDCs showed high specific capacitance and dual meso/microporous structures with high salt adsorption capacity (SAC), reaching 26.5 mg·g−1 in a single-pass desalination mode. Moreover, all NDC electrodes exhibited exceptional desalination stability performance over 150 successive charging/discharging cycles with 100% retention in aerated and deaerated solutions under harsh 1.4 V as the charging voltage. Moreover, all NDCs cells demonstrated charge efficiencies in the range from ~40 to 60%. The potential of zero charge (PZC) was determined for the tested NDC electrodes to elucidate their oxidation resistance (EOR). The electrodes exhibited a minimal shift in potential after the entire desalination stability tests, revealing minor electrode oxidation. The performance of our NDC-electrodes was compared against that of the commercially available activated carbon (AC) under the same experimental conditions, with the latter showing a server decrease in the SAC retention within the first few cycles. [Display omitted] •Synthesis of meso/microporous carbon electrodes with a controlled nitrogen content•The electrodes showed a salt adsorption capacity of 26.5 mg·g−1 in a single-pass desalination mode.•The electrodes showed exceptional cycling stability over 150 successive cycles.•The electrodes showed 100% retention in aerated and deaerated solutions under harsh 1.4 V.•The potential of zero charge (PZC) showed very high oxidation resistance.