Solute transport and reaction in porous electrodes at high Schmidt numbers

Maggiolo, Dario; Picano, Francesco; Zanini, Filippo; Carmignato, Simone; Guarnieri, Massimo; Sasic, Srdjan; Ström, Henrik

doi:10.1017/jfm.2020.344

Cited by 19 publications

(16 citation statements)

References 40 publications

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“…[ 32–35 ] Advanced numerical simulations on porous media have demonstrated that streamwise‐oriented fibers and pores can lead to increased permeabilities and improved dispersion efficiency; [ 36 ] furthermore, material sets possessing wide variability in pore sizes with high specific surface area induce higher dispersion and reaction rates, improving overall performance. [ 37–41 ] Collectively, these prior works constitute important advances in the electrochemical science and engineering of porous electrodes. However, translation beyond the lab‐scale remains a concern, as constraints inherent to existent large‐scale carbon fiber manufacturing processes necessitate the introduction of additional and often complex post‐treatments to produce electrodes with suitable performance characteristics, which results in increased production costs.…”

Section: Figurementioning

confidence: 99%

“…[32][33][34][35] Advanced numerical simulations on porous media have demonstrated that streamwise-oriented fibers and pores can lead to increased permeabilities and improved dispersion efficiency; [36] furthermore, material sets possessing wide variability in pore sizes with high specific surface area induce higher dispersion and reaction rates, improving overall performance. [37][38][39][40][41] Collectively, these prior works constitute important advances in the electrochemical science and engineering of porous electrodes. However, translation beyond the Figure 1.…”

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confidence: 99%

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Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

et al. 2021

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devices, RFB electrolyte tanks are easily accessible, enabling electrolyte scale-up, maintenance, and potential exchange of new redox couples (Figure 1a). Despite their advantages, current iterations of RFBs are considered too costly for many emerging grid applications, [1,4,5] motivating research into improved electrolyte formulations, [6,7] separation technologies, [8][9][10] operational strategies, [11] and materials design. [12] In particular, increasing power density enables more compact and efficient reactors that can meet operational demands, reducing electrochemical stack size and costs. Within the reactor, the porous carbonaceous electrode supports several important functions, including conducting electrons and heat, providing surface area for redox reactions to occur, distributing electrolyte through the reactor, and regulating the operational pressure drop. [13] Thus, the interfacial and microstructural properties influence electrochemical and fluid dynamic performance, ultimately impacting system efficiency and cost. [14] Historically, conventional RFB electrodes have been fibrous mats derived from polyacrylonitrile (PAN) precursor and assembled into coherent structures including papers, cloths, or felts. [15] Such formats are functional for convection-driven electrochemical technologies owing to their permeability (k ≈ 10 −10 to 10 −12 m 2 ), (electro)chemical stability, and electronic conductivity. Each unique fiber arrangement results in constructs with idiosyncratic Porous carbonaceous electrodes are performance-defining components in redox flow batteries (RFBs), where their properties impact the efficiency, cost, and durability of the system. The overarching challenge is to simultaneously fulfill multiple seemingly contradictory requirements-i.e., high surface area, low pressure drop, and facile mass transport-without sacrificing scalability or manufacturability. Here, non-solvent induced phase separation (NIPS) is proposed as a versatile method to synthesize tunable porous structures suitable for use as RFB electrodes. The variation of the relative concentration of scaffold-forming polyacrylonitrile to pore-forming poly(vinylpyrrolidone) is demonstrated to result in electrodes with distinct microstructure and porosity. Tomographic microscopy, porosimetry, and spectroscopy are used to characterize the 3D structure and surface chemistry. Flow cell studies with two common redox species (i.e., all-vanadium and Fe 2+/3+ ) reveal that the novel electrodes can outperform traditional carbon fiber electrodes. It is posited that the bimodal porous structure, with interconnected large (>50 µm) macrovoids in the through-plane direction and smaller (<5 µm) pores throughout, provides a favorable balance between offsetting traits. Although nascent, the NIPS synthesis approach has the potential to serve as a technology platform for the development of porous electrodes specifically designed to enable electrochemical flow technologies.

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confidence: 99%

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Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

et al. 2021

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“…Transport of dissolved substances through porous media is determined by the complexity of the velocity field in the pore space and diffusive mass transfer within and between pores. The interplay of diffusive pore-scale mixing and spatial flow variability are key for the understanding of transport and reaction phenomena in natural and engineered porous media [1][2][3] with diverse applications ranging from groundwater contamination and geological carbon dioxide storage [4], to the design of batteries [5] and transport in brain microcirculation [6].…”

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Pore-Scale Mixing and the Evolution of Hydrodynamic Dispersion in Porous Media

2021

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We study the interplay of pore-scale mixing and network-scale advection through heterogeneous porous media, and its role for the evolution and asymptotic behavior of hydrodynamic dispersion. In a Lagrangian framework, we identify three fundamental mechanisms of pore-scale mixing that determine large scale particle motion, namely, the smoothing of intrapore velocity contrasts, the increase of the tortuosity of particle paths, and the setting of a maximum time for particle transitions. Based on these mechanisms, we derive a theory that predicts anomalous and normal hydrodynamic dispersion in terms of the characteristic pore length, Eulerian velocity distribution, and Péclet number.

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“…More realistic models, based on the fibre orientation information obtained from analyzing microscopic images, were used by Wang et al [11] and Maze et al [12] In the case of air-laid filter media, 3D models can provide more accurate predictions of pressure drop and capture efficiency. [13][14][15] However, they require high computational power, which can limit their feasibility and restrict parametric studies. In this scenario, representative 2D models can be a valid alternative to simulate the flow through the filter medium, providing reliable and meaningful data when using realistic input data.…”

Section: Introductionmentioning

confidence: 99%

A simple numerical method to simulate the flow through filter media: Investigation of different fibre allocation algorithms

et al. 2021

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Flow patterns and pressure-drop through three fine-fibre air filter media were simulated using the lattice Boltzmann method. The geometry for the flow domain was two-dimensional, with fibres having truncated log-normal diameter distributions matching SEM photograph measurements on the actual media. The influence of the strategy in positioning the fibres inside the computational domain on the pressure drop of the filter media was investigated. Two different schemes were proposed to position the fibres into a cross section of the filter medium: a random distribution algorithm and the Mitchell's best candidate algorithm. Furthermore, no-slip and free-slip boundary conditions were tested for the fluid-fibre interaction. The comparison between numerical and experimental data shows that the random allocation of fibres better predicted the filter media behaviour. Simulated data suggest that the free-slip boundary condition must be used when studying the interaction of the fluid with small fibres similar to the size of the fibres used in this study. This study allowed the development of a simple strategy to estimate the pressure drop of a filter medium by having little information of its physical structure, such as solid fraction and diameter distribution.

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Solute transport and reaction in porous electrodes at high Schmidt numbers

Cited by 19 publications

References 40 publications

Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

Pore-Scale Mixing and the Evolution of Hydrodynamic Dispersion in Porous Media

A simple numerical method to simulate the flow through filter media: Investigation of different fibre allocation algorithms

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