Basis and Prospects of Combining Electroadsorption Modeling Approaches for Capacitive Deionization

Abstract

Electrically driven adsorption, electroadsorption, is at the core of technologies for water desalination, energy production, and energy storage using electrolytic capacitors. Modeling can be crucial for understanding and optimizing these devices, and hence different approaches have been taken to develop multiple models, which have been applied to explain capacitive deionization (CDI) device performances for water desalination. Herein, we first discuss the underlying physics of electroadsorption and explain the fundamental similarities between the suggested models. Three CDI models, namely, the more widely used modified Donnan (mD) model, the Randles circuit model, and the recently proposed dynamic Langmuir (DL) model, are compared in terms of modeling approaches. Crucially, the common physical foundation of the models allows them to be improved by incorporating elements and simulation tools from the other models. As a proof of concept, the performance of the Randles circuit is significantly improved by incorporating a modeling element from the mD model and an implementation tool from the DL model (charge-dependent capacitance and system identification, respectively). These principles are accurately validated using data from reports in the literature showing significant prospects in combining modeling elements and tools to properly describe the results obtained in these experiments.

A new automated model brings stability to finite‐element simulations of capacitive deionization

“…A common empirical capacitance correction states that the capacitance increases with the square of the micropore charge (Equation 13 [ 58,73–75 ] ). Here, $${C_m}$$ is the micropore capacitance [$$F/{m^3}$$], $${C_{m,0}}$$ is the constant baseline micropore capacitance [$$F/{m^3}$$], $${{\alpha}}$$ is a constant fitting parameter [$$F/({m^3}{( {mM} )^2})$$], and $${q_m}$$ is the micropore concentration of charges [mM].…”

“…Different modeling approaches has been built to describe the CDI processes including molecular dynamics, [53] transmission line, [29,54,55] dynamic Langmuir, [40,41,[56][57][58][59][60] and modified Donnan (mD) [2,11,23,61,62] models. While some macroscopic studies simplify treating the entire cell as a single 0D entity, [63] others consider spatiotemporal information through spatially resolved finite-element modeling (FEM) using software packages like COMSOL.…”

Langmuir-Based Modeling Produces Steady Two-Dimensional Simulations of Capacitive Deionization via Relaxed Adsorption-Flow Coupling

“…Hence, coupling it with a description of the charge–adsorption relationship would make it possible to describe ion adsorption on the electrodes. 72 …”

“…The point here is that the Randles circuit can simulate charging as a self-contained unit. Hence, coupling it with a description of the charge–adsorption relationship would make it possible to describe ion adsorption on the electrodes …”

Sodium to cesium ions: a general ladder mechanism of ion diffusion in prussian blue analogs

“…This makes them effective for energy storage 3 and desalination by capacitive deionization (CDI), among many potential applications. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The versatile nature of PBAs further enables applications in carbon capture, 19 Fenton reactions, 20 sensing, 21 and biomedicine. 22,23 At the extreme end, it can even be applied for cesium decontamination [24][25][26][27][28] because the huge Cs + ions can passively replace K + ions in the matrix formed by the host structure.…”