Surface-treated carbon electrodes with modified potential of zero charge for capacitive deionization

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Engineering

Background:

• The potential of zero charge (Epzc) of electrodes is critical for capacitive deionization (CDI) performance, affecting salt removal, charge efficiency, and stability.
• Optimizing Epzc is essential for developing high-performance CDI systems.

Purpose of the Study:

• To develop a simple method for negatively shifting the Epzc of CDI electrodes.
• To evaluate the capacitive deionization performance of electrodes with optimized Epzc.

Main Methods:

• Commercial activated carbon was modified with quaternized poly(4-vinylpyridine) (AC-QPVP) to create composite electrodes.
• The Epzc of the AC-QPVP electrode was determined to be -0.745 V vs. Ag/AgCl.
• An asymmetric CDI cell was constructed using AC-QPVP and nitric acid-treated activated carbon (AC-HNO3) electrodes.

Main Results:

• The AC-QPVP composite electrode exhibited a significantly negative Epzc.
• The asymmetric CDI cell demonstrated excellent performance, with a working potential window of 1.4 V in inverted CDI mode.
• A salt removal capacity of 9.6 mg/g was achieved in inverted CDI, and 20.6 mg/g in extended voltage CDI, comparable to membrane CDI.

Conclusions:

• A straightforward method for preparing highly positively charged CDI electrodes was established.
• The optimized Epzc of electrodes significantly enhances CDI performance, offering a promising approach for developing efficient water desalination technologies.