Inverted capacitive deionization (i-CDI) is examined using microporous Spectracarb carbon electrodes in 10 mmol L-1 NaCl solution without deaeration. i-CDI testing shows that using conventional operational methods, i.e., Vch = 0.8 V and Vdis = 0 V (0.8/0 V), cannot stabilize salt separation after approximately 409 h with an averaged salt adsorption capacity (SAC) of 6.0 ± 0.8 mg g-1. The cycled anode possesses a collapsed cyclic voltammogram due to an increase in the sheet resistance by the formation of a surface oxide layer. This layer eventually suppresses electronic charge utilization in the i-CDI cell causing degraded salt separation. By analysis of potential distributions incorporated with the modified Donnan model, an improved i-CDI operational method is proposed by reducing Vch to 0.4 V and Vdis to -0.4 V (0.4/-0.4 V) while maintaining a voltage window (Vch-Vdis) of 0.8 V. The improved i-CDI testing demonstrates that not only is the separation process stabilized up to approximately 420 h but the SAC also increases to 7.2 ± 0.3 mg g-1. Additionally, operation at 0.4/-0.4 V possesses more stable pH and dissolved oxygen (DO) responses than that at 0.8/0 V. We believe that such improved performance stems from a reduced Vch mitigating carbon oxidation at the anode and DO reduction at the cathode while the reduced Vdis compensates for salt removal capacity.
|Number of pages||11|
|Journal||Journal of Physical Chemistry C|
|State||Published - Jan 18 2018|
Bibliographical noteFunding Information:
This work was supported by the U.S.−China Clean Energy Research Center, U.S. Department of Energy [DE-PI0000017]. These authors thank Mr. R. Perrone for help in designing and constructing the flow-through cell stack.
© 2017 American Chemical Society.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Energy (all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films