Electrosorption capacitance of nanostructured carbon-based materials

Hou, Chia‐Hung; Liang, Chengdu; Yiacoumi, Sotira; Dai, Sheng; Tsouris, Costas

doi:10.1016/j.jcis.2006.06.009

Cited by 153 publications

(80 citation statements)

References 26 publications

(39 reference statements)

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“…The presence of micropores is an essential feature in the high specific surface area of carbon electrode. On the other hand, mesopores have fast charging rate of ions in the electrosorption process (Hou et al 2006). A carbon electrode, composed of both micropores and mesopores, constitutes a favorable capacitor electrode material due to both high double layer capacity and high electrosorption rate (Noked et al 2009;Villar et al 2011).…”

Section: Porous Structurementioning

confidence: 99%

“…The cutoff width decreased with increasing the solution concentration, and then smaller pores can contribute to electrosorption. A further understanding of the overlapping effect on capacitive behavior of carbon electrodes was carried out using voltammetric technology (Yang et al 2003;Hou et al 2006). EDL overlapping reduces the double layer capacitance in terms of the number of ions electroadsorbed within carbon electrodes.…”

Section: Introductionmentioning

confidence: 99%

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Application of capacitive deionization technology to the removal of sodium chloride from aqueous solutions

Hou

Huang

2013

Int. J. Environ. Sci. Technol.

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Capacitive deionization has been developed as a promising desalination alternative for removing ions from aqueous solutions. In this study, the evaluation of capacitive performance was carried out by galvanostatic charge/discharge and cyclic voltammetry experiments. The good capacitive and electrosorption behaviors suggest carbon aerogel not only treated as an electrical double layer capacitor, but also as a potential electrode in capacitive deionization processes. Also, the capacitive deionization characteristics indicate that electrosorption/regeneration can be controlled by polarization and depolarization of each electrode. It implies that sodium and chloride ions are electrostatically held to form electrical double layer on the surface of charged electrodes. The electrosorption performance at different applied voltages and solution concentrations was investigated. It is found that the removal of sodium chloride increases with increasing applied voltage and solution concentration, resulting from stronger electrostatic interactions, higher concentration gradient, and less double layer overlapping effect. Based on Langmuir isotherm, the equilibrium electrosorption capacity at 1.2 V is determined as 270.59 lmol/g. Under this condition, due to the presence of micropores associated with the double layer overlapping, the effective surface area for electrosorption of ions at 1.2 V is estimated in the range of 12.18-14.25 % of the BrunauerEmmett-Teller surface area. The results provide a fundamental understanding of electrosorption of ions and help promoting capacitive deionization technology for water purification and desalination.

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Section: Porous Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Application of capacitive deionization technology to the removal of sodium chloride from aqueous solutions

Hou

Huang

2013

Int. J. Environ. Sci. Technol.

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“…In many cases, it is important to describe the possibility that the EDLs overlap within a finite pore thickness comparable to the Debye length, as in the case of nanoscale cylindrical or slitlike pores [29,32]. In the limit that the EDLs overlap strongly, i.e., the limit that the Debye length is much larger than the typical pore size, it is possible to assume a constant electrostatic potential in the pore space.…”

Section: Introductionmentioning

confidence: 99%

Diffuse charge and Faradaic reactions in porous electrodes

2011

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Porous electrodes instead of flat electrodes are widely used in electrochemical systems to boost storage capacities for ions and electrons, to improve the transport of mass and charge, and to enhance reaction rates. Existing porous electrode theories make a number of simplifying assumptions: (i) The charge-transfer rate is assumed to depend only on the local electrostatic potential difference between the electrode matrix and the pore solution, without considering the structure of the double layer (DL) formed in between; (ii) the charge-transfer rate is generally equated with the salt-transfer rate not only at the nanoscale of the matrix-pore interface, but also at the macroscopic scale of transport through the electrode pores. In this paper, we extend porous electrode theory by including the generalized Frumkin-Butler-Volmer model of Faradaic reaction kinetics, which postulates charge transfer across the molecular Stern layer located in between the electron-conducting matrix phase and the plane of closest approach for the ions in the diffuse part of the DL. This is an elegant and purely local description of the charge-transfer rate, which self-consistently determines the surface charge and does not require consideration of reference electrodes or comparison with a global equilibrium. For the description of the DLs, we consider the two natural limits: (i) the classical Gouy-Chapman-Stern model for thin DLs compared to the macroscopic pore dimensions, e.g., for high-porosity metallic foams (macropores >50 nm) and (ii) a modified Donnan model for strongly overlapping DLs, e.g., for porous activated carbon particles (micropores <2 nm). Our theory is valid for electrolytes where both ions are mobile, and it accounts for voltage and concentration differences not only on the macroscopic scale of the full electrode, but also on the local scale of the DL. The model is simple enough to allow us to derive analytical approximations for the steady-state and early transients. We also present numerical solutions to validate the analysis and to illustrate the evolution of ion densities, pore potential, surface charge, and reaction rates in response to an applied voltage.

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“…However, for porous electrodes where most of the charge and ion storage occurs inside much smaller micropores, such as most electrodes prepared, e.g., from porous carbon particles, the GCS-model cannot be applied. Modifications are possible to consider partial EDL overlap [48][49][50][51] but these models are mathematically more involved when differences in (counter-vs. co-) ion adsorption are to be described. Therefore, it is useful to consider the opposite limit of the GCS-model, namely that the Debye length is much larger (not smaller) than the typical micropore size.…”

Section: Introductionmentioning

confidence: 99%