Characterizing and mitigating the degradation of oxidized cathodes during capacitive deionization cycling

Uwayid, Rana; Seraphim, Nicola M.; Guyes, Eric N.; Eisenberg, David; Suss, Matthew E.

doi:10.1016/j.carbon.2020.11.045

Cited by 32 publications

(43 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to the long-term F-CapMix result in Figure e, long-term power densities of flow electrodes have been confirmed to have the same tendency as F-CapMix results, as shown in Figure c. A decrease in power densities of both AC and EG flow electrodes is expected to be caused by a decrease in salts in flow electrodes and oxygen evolution reactions from oxygen-containing functional groups on AC and EG surfaces due to desalination performance degradation caused by oxygen evolution reactions in the previous report . Further studies on the mechanism of degradation during the F-CapMix process should be conducted.…”

Section: Resultssupporting

confidence: 66%

Cross Effect of Surface Area and Electrical Conductivity for Carbonaceous Materials in Flow-electrode Capacitive Mixing (F-CapMix) and Flow-electrode Capacitive Deionization (FCDI): Solid-like Behavior of Flow-electrode

Hwang

Lee

Jung

et al. 2021

ACS Sustainable Chem. Eng.

View full text Add to dashboard Cite

Flow-electrode capacitive mixing (F-CapMix) and flow-electrode capacitive deionization (FCDI) systems are promising for energy generation and desalination devices, respectively, because constant energy generation and desalination are possible without an intermittent step by employing continuously flowing electrodes. Activated carbon (AC) has been widely used as a flow electrode material for F-CapMix and FCDI due to its good phase stability in an aqueous medium and large surface area capable of ion adsorption. However, the relationship between the physicochemical properties of carbonaceous materials and device performances has not been systematically studied. In this study, we explore activated carbon, natural graphite, synthetic graphite, and expanded graphite with similar particle sizes to a flow electrode material to understand dominant parameters in terms of material properties for the high-performance F-CapMix system and comparison with the FCDI system. The physicochemical properties of carbonaceous materials, their rheological behaviors in an aqueous medium, and corresponding electrochemical properties are systematically studied. Among them, the flow electrode prepared with expanded graphite shows the highest power density of 0.48 W/m2 in F-CapMix due to its solidlike rheological behavior as well as high electrical conductivity and a relatively low FCDI performance of 2.7%. Our findings suggest that the internal resistance of the flow electrode, which is closely related to rheological behavior and powder electrical conductivity, is a dominant factor for the high power density in F-CapMix. In addition, the high specific surface area of carbon material and rheological behavior of the flow electrode are dominant factors for the high salt removal efficiency of the FCDI system.

show abstract

Section: Resultssupporting

confidence: 66%

Cross Effect of Surface Area and Electrical Conductivity for Carbonaceous Materials in Flow-electrode Capacitive Mixing (F-CapMix) and Flow-electrode Capacitive Deionization (FCDI): Solid-like Behavior of Flow-electrode

Hwang

Lee

Jung

et al. 2021

ACS Sustainable Chem. Eng.

View full text Add to dashboard Cite

show abstract

“…Activated carbon cloth (ACC-5092-15, Kynol GmbH) with

600

thickness,

0.53

specific micropore volume, and

1,400

surface area ( 56 ) was used as the electrode material. This material was characterized in several previous CDI studies ( 47 , 53 , 56 , 78 , 85 – 89 ). The carbon was cut into electrode squares with a cross-sectional area of

6.25

.…”

Section: Methodsmentioning

confidence: 99%

“…4 ). The parameters used to describe the electrodes are based on previous works ( 53 , 56 , 78 , 87 , 89 ); characterization experiments which are described in detail in SI Appendix , Section S3 ; and, in the case of the theoretical analysis ( Fig. 4 and the third column of Table 2 ), the values assumed for hypothetical pristine (as given) electrodes with equal amount of acidic and basic chemical surface groups.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical removal of amphoteric ions

Shocron

Guyes

Rijnaarts

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Several harmful or valuable ionic species present in seawater, brackish water, and wastewater are amphoteric, weak acids or weak bases, and, thus, their properties depend on local water pH. Effective removal of these species can be challenging for conventional membrane technologies, necessitating chemical dosing of the feedwater to adjust pH. A prominent example is boron, which is considered toxic in high concentrations and often requires additional membrane passes to remove during seawater desalination. Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into charging microporous electrodes. CDI cells show strong internally generated pH variations during operation, and, thus, CDI can potentially remove pH-dependent species without chemical dosing. However, development of this technique is inhibited by the complexities inherent to the coupling of pH dynamics and ion properties in a charging CDI cell. Here, we present a theoretical framework predicting the electrosorption of pH-dependent species in flow-through electrode CDI cells. We demonstrate that such a model enables insight into factors affecting species electrosorption and conclude that important design rules for such systems are highly counterintuitive. For example, we show both theoretically and experimentally that for boron removal, the anode should be placed upstream and the cathode downstream, an electrode order that runs counter to the accepted wisdom in the CDI field. Overall, we show that to achieve target separations relying on coupled, complex phenomena, such as in the removal of amphoteric species, a theoretical CDI model is essential.

show abstract

“…3,4 Although CDI is a promising technology for brackish water desalination, stable long-term operation remains a challenge. 3,5 In addition to capacitive ion storage in EDLs, undesirable Faradaic processes also occur. 6,7 These Faradaic processes are considered to be the main reason for a decrease in desalination performance over time.…”

Section: ■ Introductionmentioning

confidence: 99%

Unravelling pH Changes in Electrochemical Desalination with Capacitive Deionization

Arulrajan

Dykstra

Wal

et al. 2021

Environ. Sci. Technol.

View full text Add to dashboard Cite

Membrane capacitive deionization (MCDI) is a water desalination technology employing porous electrodes and ion-exchange membranes. The electrodes are cyclically charged to adsorb ions and discharged to desorb ions. During MCDI operation, a difference in pH between feed and effluent water is observed, changing over time, which can cause the precipitation of hardness ions and consequently affect the long-term stability of electrodes and membranes. These changes can be attributed to different phenomena, which can be divided into two distinct categories: Faradaic and non-Faradaic. In the present work, we show that during long-term operation, as the electrodes age over time, the magnitude and direction of pH changes shift. We studied these changes for two different feed water solutions: a NaCl solution and a tap water solution. Whereas we observe a pH decrease during the regeneration with a NaCl solution, we observe an increase during regeneration with tap water, potentially resulting in the precipitation of hardness ions. We compare our experimental findings with theory and conclude that with aged electrodes, non-Faradaic processes are the prominent cause of pH changes. Furthermore, we find that for desalination with tap water, the adsorption and desorption of HCO3 –and CO3 2– ions affect the pH changes.

show abstract

Characterizing and mitigating the degradation of oxidized cathodes during capacitive deionization cycling

Cited by 32 publications

References 59 publications

Cross Effect of Surface Area and Electrical Conductivity for Carbonaceous Materials in Flow-electrode Capacitive Mixing (F-CapMix) and Flow-electrode Capacitive Deionization (FCDI): Solid-like Behavior of Flow-electrode

Cross Effect of Surface Area and Electrical Conductivity for Carbonaceous Materials in Flow-electrode Capacitive Mixing (F-CapMix) and Flow-electrode Capacitive Deionization (FCDI): Solid-like Behavior of Flow-electrode

Electrochemical removal of amphoteric ions

Unravelling pH Changes in Electrochemical Desalination with Capacitive Deionization

Contact Info

Product

Resources

About