Figure - available from: Journal of The Electrochemical Society
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Effect of FTE parameters (i avg, d, and L) on WaI and WaII: (a) Constant L, varying d and (b) Constant d, varying L. Thicker lines represent design regime where WaII ≫ WaI > 6.
Source publication
![(a) Steady-state polarization for the [Fe(CN)6]4– ⇌ [Fe(CN)6]3– redox...](publication/350882811/figure/fig5/AS:11431281208137532@1701376390054/a-Steady-state-polarization-for-the-FeCN64-FeCN63-redox-reaction-on-a_Q320.jpg)
The tubular flow-through electrode (FTE) is a facile electroanalytical tool for investigating electrochemical reaction kinetics; however, its suitability for this purpose requires careful design and operation under conditions that guarantee uniform current distribution. In this perspective article, we provide a scaling analysis of the transport and...
Citations
... Figure 4. shows how the redox species concentration and the potential scan rate modulate the peak current and thus the Wagner number (Eq. 3). For example, for solutions of 10 mM HT in ethaline, scan rates below 0.4 V/s generate peak current densities of 0.83 mA cm −2 or lower, representing uniform current distribution (Wa > 5, typical criterion for uniformity of the secondary current distribution 21 ). Conditions were chosen in Figs. ...
Deep eutectic solvents (DESs) have recently gained interest as flow battery electrolytes. Their advantages include a wider electrochemical stability window compared to aqueous electrolytes, higher solubility for redox-active species, and negligible volatility. However, DESs are often highly viscous, and suffer from low ionic conductivities. This can make assessing redox kinetics difficult when attempting to determine their viability for energy storage. In classical voltammetric measurements, low ionic conductivity manifests as high solution resistance, thereby requiring ‘live’ compensation of the electrolyte ohmic drop when performing fast-scan voltammetry. An uncompensated or inadequately-compensated ohmic drop leads to misinterpretation of the voltammetric behavior, e.g., assessing reversibility vs. irreversibility of a redox reaction. Here, we present micro-fabricated electrodes as facile ‘meso-scale’ electrodes, which overcome these issues by nearly eliminating the ohmic drop while retaining uniformity of the current distribution over the electrode surface. Their use in precise transport-kinetics measurements is demonstrated using a redox-active organic, i.e., 4-Hydroxy-TEMPO in an aqueous medium and in ethaline, which is a viscous DES. This study provides a methodical approach to design and implement voltammetry experiments using meso-scale electrodes leading to reliable measurements of diffusion-reaction properties of 4-Hydroxy-TEMPO.
... Electrodeposition is carried out under flow conditions to mitigate concentration polarization. 23 A Cu 2 SO 4 /Na 2 SO 4 electrolyte bath featuring high faradaic efficiency is used to deposit high purity metallic copper within graphite tubular flow-through electrodes (FTE). We assess the thickness and uniformity of the electroplated copper coating inside the graphite FTE using micro-computed X-ray tomography (μCT) to validate the model. ...
... The classical Wagner number (Wa I ) represents the ratio of activation and ohmic resistances, and is widely used in electrochemical systems analysis. 31,32 As described in our previous work, 23 Wa I for an FTE can be defined as (Eq. 8): ...
The emergence of advanced manufacturing methods capable of producing porous three-dimensional structures has expanded the design space for next-generation functional components. The ability to fabricate ordered 3D foams for use in electrocatalysis reactors has increased the need for controlled deposition of catalytic metals onto porous support materials, such as carbon. However, there is a lack of clear design guidelines for electrodeposition onto 3D substrates, due to the geometric complexity and multi-scale nature of the problem. Furthermore, electro-nucleation phenomena are often overlooked in macro-scale models of current distribution during deposition. Here, a graphite flow-through electrode is used as a model system for copper deposition within a single pore. Potential distributions and electro-nucleation phenomena are coupled in a continuum level model by incorporating nucleation size and density as a function of overpotential, determined experimentally using in-situ atomic force microscopy. The model predictions are validated by measuring the coating uniformity in the pore using micro-computed X-ray tomography. A scaling analysis comprising dimensionless parameters such as the Wagner number is presented. The simplified scaling relationship framework can guide the electrodeposition process and electrode design to optimize plating of porous substrates under fluid flow conditions.
