bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Electropolymerization of Aromatic Monomers Using Streaming Potentials
Authors: Iwai Suguru , Shida Naoki , Tomita Ikuyoshi , Inagi Shinsuke
Published: July 2022

Recently, there has been increasing attention on bipolar electrodes which work as a wireless electrode in the presence of external electric field.1 Since bipolar electrodes are driven with low concentration of supporting electrolytes, an electrosynthesis process using bipolar electrode can reduce the amount of waste after the electrolysis. We have already reported the electrochemical fluorination using a bipolar electrode system, in which the amount of supporting electrolyte used could be reduced to less than 1/100 compared to the conventional method.2 On the other hand, when pumping the solution with low concentration of supporting electrolyte into a narrow channel, potential difference between inlet and outlet of the channel, i.e., a streaming potential, generates to potentially be a driving energy for a bipolar electrode system.3

In this study, we have investigated the conditions in a flow cell to generate enough streaming potentials for electrode reactions. Then, electropolymerization of aromatic monomers such as pyrrole and 3,4-ethylenedioxythiophene has been achieved by driving a bipolar electrode using a streaming potential.

References

N. Shida, Y. Zhou, S. Inagi, Acc. Chem. Res., 2019, 52, 2598–2608.

K. Miyamoto, H. Nishiyama, I. Tomita, S. Inagi, ChemElectroChem, 2019, 6, 97–100.

I. Dumitrescu, R. K. Anand, S. E. Fosdick, R. M. Crooks, J. Am. Chem. Soc., 2011, 133, 4687–4689.

Figure 1
Controlling Surface-Immobilized Elastin-like Peptides for Electrochemical Sensing Applications
Authors: Renner Julie N. , Pramounmat Nuttanit , Su Zihang
Published: July 2022

Surface-immobilized elastin-like peptides (ELPs), known for their stimuli-responsive behavior, represent a promising biomolecular platform for electrochemical sensing. Key to the success of this applications is understanding how ELPs assemble on electrode surfaces, how the assembly and configuration can be controlled, and how their structure impacts the accessibility of the solid surface to redox active species. Here, we share recent work where short ELPs with varying guest residues and sequence length were designed for gold electrode attachment, and the ability of a redox probe to access a gold surface was characterized by cyclic voltammetry. From these results, a quantitative model describing the relationship between ELP effective surface coverage as a function of the mean hydrophobicity and mass loading was elucidated, illustrating the ability to precisely control surface properties by tuning the ELP sequence. In addition, strategies for controlling surface-bound ELP assembly and properties will be discussed. Ultimately, our work demonstrates that controlling the assembly and ELP configuration on the solid surface leads to more favorable electrochemical sensing capacity.
(Invited) Extracting Kinetics from Scanning Electrochemical Microscopy Images through Least-Squares Fitting of Reactive Discs
Authors: Leslie Nathaniel , Mena Morcillo Emmanuel , Morel Alban , Mauzeroll Janine
Published: July 2022

The strength of scanning electrochemical microscopy measurements (SECM) is its ability to give insights into the kinetics of an underlying surface. Up to now there was no established way to extract kinetics from an SECM image. Our study fills this gap by proposing a method that fits the active area and kinetics of reactive sites from SECM images using the Levenberg-Marquardt algorithm and finite element method simulations.

Currently, the kinetics of reactions at a surface are quantified through SECM by performing approach curves: measuring the SECM current as the microelectrode approaches a surface vertically.[1] The theory used to fit approach curves assumes that the kinetics at the surface are uniform across an infinitely large surface. Realistically, sites at which reactions occur in SECM imaging are not infinitely large, leading to an under-estimation of kinetics at finite reactive sites. In some cases, approach curve theory can misidentify diffusion-limited surface reactions at small sites as being electron-transfer-limited. Our new method instead assumes that reactive sites are uniformly reacting discs. High agreement between the fitted and true areas of reactive sites are shown for both simulated and experimental SECM images. Less than 10% error was common for nearly-circular reactive sites. Diffusion-limited processes are not mislabelled as electron-transfer-limited by this method. The rate constants for electron-transfer-limited reactions were usually fit to within 15% error, much lower than the error experienced by the approach-curve method when applied to finite reactive sites.

[1] C. Lefrou, R. Cornut, Analytical Expressions for Quantitative Scanning Electrochemical Microscopy (SECM). ChemPhysChem
2010, 11, 547-556.
Using Complex Collection Efficiency for Detection of Oxidation Products – Examples from Hydrogen Evolution, Oxygen Evolution and CO2 Reduction
Authors: Holm Thomas , Diaz-Real Jesus Adrian
Published: July 2022

Electrochemical reactions can often yield a distribution of products, for example for CO2 reduction on Cu and methanol oxidation on Pt. This distribution varies with (over)potential and catalyst type, and usually requires the experimenter to incorporate detectors such as mass spectrometry or gas chromatography into their experimental setup. Electrochemical methods also exist, such as using the rotating ring-disk electrode or the analogous double channel electrodes. However, these methods suffer from unsteady measurements, and are hard to do with the desired accuracy. Techniques using alternating current perturbations may be an improvement here and preliminary work on transfer functions for product detection show promise, here called complex collection efficiency (CCE)[1]. This technique has the advantage that it reduces or removes the influence of parasitic currents on the electrodes and can yield the product distribution as a function of current density and/or electrode potential. In this work, CCE was tested on a lab made microfluidic system with double channel electrodes and measurements were done on ideal reactions with a single product, the hydrogen evolution reaction and oxygen evolution reaction to optimize and calibrate the setup, see Figure 1. Finally, CO2 reduction on Ag was attempted and compared with literature values as this primarily yields CO and H2 as the reaction products.

Holm, T., J.A. Diaz Real, and W. Mérida, Numerical modeling of complex collection efficiency for double channel electrodes. Journal of Electroanalytical Chemistry, 2019. 842: p. 115-126.

Figure 1
Why Methanol Electro-Oxidation on Platinum in Water Takes Place Only in the Presence of Adsorbed OH
Authors: Aran-Ais Rosa , Mekazni Dalila S. , Ferre-Vilaplana Adolfo , Herrero Enrique
Published: July 2022

To optimize fuel cells performance using alcohols as fuel it is essential to untangle the mechanism of the methanol electro-oxidation on platinum in aqueous medium as a model reaction. Recent studies have pointed out the particular necessity of adsorbed OH for this electro-oxidation process to take place1. The here reported results, carefully obtained under low methanol concentrations on the three basal planes of platinum at different scan rates to discriminate between oxidation and adsorption processes, confirm such an unforeseen preceding observation2. It is elucidated that only when adsorbed OH is already present on the surface, adsorbed CO from methanol is formed. This observation is a clear indication that adsorbed OH is involved in the mechanism beyond providing the oxygen group required to oxidize adsorbed CO, which has never been considered before. The role played by adsorbed OH in the methanol electro-oxidation to CO on platinum in aqueous medium is supported by DFT calculations, as well as the reason why this reaction is not observed in the absence of adsorbed OH. A combination of kinetic and thermodynamic factors, such as the presence of multiple water molecules per methanol molecule, the high adsorbed OH mobility on the surface, the favorable co-adsorption of methanol in the presence of adsorbed OH, and the favorable and virtually barrier-less hydrogen transference from the hydroxy group of methanol to adsorbed OH to yield water, result in the immediate activation of methanol (as soon as the molecule approaches the surface) through the favorable substitution of adsorbed OH by adsorbed methoxy. In this contribution it will be presented a change of paradigm in the understanding of how alcohols are electro-oxidized in reference systems thus having crucial implications in the search for better electrocatalysts.

References:

(1) Kamyabi, M. A.; Martínez-Hincapié, R.; Feliu, J. M.; Herrero, E. Effects of the Interfacial Structure on the Methanol Oxidation on Platinum Single Crystal Electrodes. Surfaces . 2019. https://doi.org/10.3390/surfaces2010014.

(2) Mekazni, D. S.; Arán-Ais, R. M.; Ferre-Vilaplana, A.; Herrero, E. Why Methanol Electro-Oxidation on Platinum in Water Takes Place Only in the Presence of Adsorbed OH. ACS Catal.
2022.
Enhancing Alcohol Oxidation Activity Using Carbon-Modified Silicon Oxide Encapsulated Pt Electrodes
Authors: Beatty Marissa , Haley Alexis T. , Llewelyn Nicole , Esposito Daniel V.
Published: July 2022

The performance of direct alcohol fuel cells (DAFCs) is frequently constrained by the efficiencies of the electrocatalysts used for the necessary alcohol oxidation reactions (AORs), which require high overpotentials to remove poisoning CO intermediates from the catalyst surface. Silicon Oxide (SiOx) encapsulated Pt electrodes have previously been shown to reduce the potential required to remove CO, and greatly enhance the activity of Pt-based catalysts for alcohol oxidation. To better understand the mechanism of this enhancement, silicon oxide layers with varying concentrations of residual carbon were employed to probe the compositional effects of overlayer composition on AORs. Overall, it was found that carbon-free, SiOx encapsulated samples exhibited the largest reduction in CO oxidation potential, with carbon rich samples still demonstrating a slight decrease in required potential compared to unencapsulated, bare Pt. Surprisingly, samples that demonstrated the largest reductions in CO oxidation potentials did not show the highest activity enhancement for alcohol oxidation. Instead, samples that had the highest concentration of carbon showed the highest degree of current enhancement for formic acid, methanol, and ethanol oxidation. For larger alcohols like propanol and butanol, the measured activity for alcohol oxidation on encapsulated samples began to diminish, credited to the additional mass transport resistance that the overlayer introduces. These observations offer insights into how the composition and properties of SiOx overlayers can affect the reactivity and transport of species in an electrochemical system, and offer an additional level of design for the development of future electrocatalyst architectures.
An Aqueous-Based BiVO4 Precursor for Controlled and Enhanced Properties Towards Water Splitting
Authors: Cardenas-Martinez Jessica , Holm Thomas , Diaz-Real Jesus Adrian
Published: July 2022

Electrochemical deposition of Bi is often obtained from non-aqueous solutions due to its natural instability in water-based solutions. In this work, we report an easy and highly reproducible method for Bi deposition on optical conductive supports as a precursor for BiVO4 synthesis. After obtaining BiVO4 from the Bi layers through hydrothermal reaction with a vanadyl precursor, the material is further modified via potentiodynamic polarization as previously demonstrated for TiO2-based materials [1]. Such a modification was used to prepare the BiVO4 electrodes for further Ni-based (NiOOH) electrocatalyst decorations [2]. The formed interfaces are studied using (photo)electrochemical and physicochemical methods to evaluate its activity towards oxygen evolution reaction. The results suggest, after tailored layer control, a comparable efficiency for the BiVO4 based on electrochemical deposition from aqueous solutions and methods based on organic solvents. Finally, electrochemical modification seemed to have a positive effect on the BiVO4 performance towards oxygen evolution. Thus, this work demonstrates a cheaper and simpler synthesis route for BiVO4 precursors and a simple method for activity modification without adding extra synthesis steps resulting in highly efficient BiVO4 photocatalysts.

Figure 1. (upper left) Electrochemical setup for Bi deposition. (lower left) Cyclic voltammograms for Bi deposition. (Right) Photographs of several BiVO4 synthesis stages.

Figure 1
(Digital Presentation) Highly Sensitive Detection of Cell Endogenous Hydrogen Sulfide Based on in-Situ Dynamic Reaction of Ag NPs
Authors: Zhou Haifeng
Published: July 2022

The performance of nanoscale sensors can often provide insights into the extremely subtle differences between biomolecules. Meanwhile, several innovative signal transduction pathways of biosensing systems have attracted a lot of attention, but most of these are always driven by a single mechanism[1]. Herein, we demonstrate a biosensor for in situ quantification of active sulfide in the cell that utilizes the electrochemical solid-state phase transformation mechanism of the self-assembled silver nanoparticles[2], which is immobilized on the surface of the gold microelectrode through Raman signal molecules (4-aminothiophenol, 4-ATP). Taking the detection of cell endogenous hydrogen sulfide (H2S) as an example, Ag NPs could first slowly react with local H2S. Under the occurrence of the electrochemical oxidation reaction, a large number of silver ions (Ag+) are released to quickly react with H2S. Subsequently, the execution of the reduction reaction brings the complex complexes to the electrode surface. The electrochemical solid-phase transfer mechanism has a fast reaction rate, and the shift of the redox peak of Ag NPs and the strength of the Raman spectrum of 4-ATP can quickly and accurately quantitatively analyze the cell endogenous H2S with two channels, and the detection limit can reach nanomolar level. Going beyond conventional biosensing, the elaborate dynamic coupling of multiple mechanisms in a micro/nanoscale interface may open a new approach for future highly sensitive biosensing.

References

[1] H Zhou, G Ran, JF Masson, C Wang, Y Zhao, Q Song, Analytical Chemistry
2018, 90(5), 3374-3381

[2] H Zhou, R Yu, G Ran, S Moussa, Q Song, J Mauzeroll, JF Masson, Sensors and Actuators B: Chemical
2020, 319, 128315
(Digital Presentation) Investigation of the Hexylamine Adsorption on Platinum By Potentiostatic and Potentiodynamic Methods
Authors: Ostapenko Gennady I. , Kalashnikova Nina A.
Published: July 2022

Adsorption is one of the electrochemical process stages often. The adsorption of polar organic molecules (surfactants) on metal electrodes is of significant interest. In particular, the surfactant adsorption affects the exchange current value and determines the metal corrosion rate. Therefore, the explanation of the adsorption mechanism is the most important problem in the investigation of the electrochemical kinetics.

The kinetics of the Fe2+ and Fe3+ oxidation-reduction reaction on a platinum electrode in 1 M HClO4 was investigated by potentiodynamic and chronoamperometric methods in the presence of hexylamine as a surfactant. The main kinetic characteristics of the reaction (exchange current density, transfer coefficient, diffusion coefficients of iron ions) have been determined.

The dependence of the exchange current density on the hexylamine concentration is analyzed. The surface coverage with a surfactant was estimated at various hexylamine concentrations. It was shown that the hexylamine adsorption on platinum is described by the Dhar-Flory-Huggins adsorption isotherm. The values of the adsorption constant and the adsorption free energy are obtained. These values are close to the corresponding values for the hexylamine adsorption on mild steel in hydrochloric acid. Consequently, the objective laws for the hexylamine adsorption depend low on the acid type and the electrode nature. This indicates the physical adsorption of the surfactant.

It is possible that adsorption occurs due to the hydrophobic interaction of the surfactant molecules with polar water molecules. Then, the displacement of surfactant molecules to the interface takes place regardless of the nature of the acid and the metal contacting with the solution. The latter assumption requires further investigations of the surfactant adsorption on various metals.
Transforming Silicon Slag into High-Capacity Anode Material for Lithium-Ion Batteries
Authors: Heitz Alexandre , Vanpeene Victor , Herkendaal Natalie , Soucy Patrick , Douillard Thierry , Roué Lionel
Published: July 2022

Silicon is mainly produced by carbothermic reduction of silica. This process generates a by-product called silicon slag, which consists mainly of a mixture of Si, SiC and C. This silicon slag represents considerable energy and material losses. On the other hand, the production of cheaper and more environmentally friendly electrode materials is essential for Li-ion battery manufacturers.

In this study, it is demonstrated that this waste containing 65 wt% Si, 31 wt% SiC and 4 wt% C can be valorized as low-cost high-capacity LiB anode material. After 20 h of high-energy ball-milling, C is fully converted to SiC and a micrometric powder is obtained in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix (Fig. 1a). This material displays a specific discharge capacity ≥1100 mAh g-1 at a current density ≤ 0.9 A g-1 (Fig. 1b) and an areal capacity ≥3.5 mAh cm-2 for at least 100 cycles (Fig. 1c). Moreover, calendering has no negative impact on the electrode performance (Fig 1d). The dQ/dV curves (Fig. 1e) do not shown intense-sharp anodic peak at about 0.45V characteristic of the delithiation of the c-Li15Si4 phase, suggesting that its formation is here prevented. This may be beneficial for the electrode cycle life as the formation of c-Li15Si4 phase is well-known to accentuate the particle cracking. However, a progressive and irreversible increase of the electrode mass and thickness is observed over cycling (reaching 125% and 60% after 200 cycles, respectively) (Fig. 1f), which is mainly attributed to the accumulation of solid electrolyte interphase (SEI) products in the electrode.

Figure 1
Investigation and Design of Soybean-Derived Carbon Anode Materials for Potassium-Ion Battery Applications
Authors: Tao Li , Liu Liang , Chang Ruofei , He Huibing , Zhao Peter , Liu Jian
Published: July 2022

Lithium-ion battery (LIBs) system is one the most widely used energy storage systems in today’s renewable energy field. However, with the dramatically increased demand over the past decades and limited core material storage, concerns arise regarding its sustainability and large-scale applications. While trying to make more efficient LIBs, the studies of alternative battery systems also appear to be more and more critical. Among many newly studied battery systems, Potassium-ion batteries (PIBs) have caught our attention. With the advantage of high abundance of Potassium (K) and low redox potential of K/K+ (2.93 V vs. standard hydrogen electrode), it appears to be a perfect candidate for substituting many of the current LIBs applications. However, the absence of a suitable carbon anode has hindered the development of PIBs. Herein, we used low-cost and abundant soybean as base material and developed a high-performance hard carbon anode for PIBs. Hard carbon, produced with 500 degrees process, exhibited the highest discharge capacity of 225 mA h g-1, long lifetime of 900 cycles, and good rate capability. Benefited from low activation temperature, the soybean-derived carbon has a medium surface area, large interplanar spacing graphene layers and low degree of graphitization, which are favored by the adsorption-dominated K-ion storage mechanism. To further improve the anode efficiency, a thin layer of Al2O3 coating (~ 2 nm) was applied on the hard carbon by Atomic Layer Deposition (ALD) to function as artificial solid electrolyte interphase and increased the Coulombic efficiency from 99.0% to 99.6%. After investigating the relationship among electrochemical performance, material interface, structural design, and mechanism of potassium-ion storage, we provided new insights for the design and synthesis of carbonaceous materials with improved storage capacity and efficiency for future developments of PIBs.
Electrode Design for High-Power Sodium-Ion Batteries: Cr Doping into Nasicon-Structured Na3V2(PO4)3 Cathode with Self-Carbon-Coating
Authors: Lee Jun , Hwang Jang-Yeon , Kim Jaekook
Published: July 2022

NASICON-structured Na3V2(PO4)3 (NVP) is one of the most promising cathode material for rechargeable sodium-ion batteries. NVP is characterized by a robust 3D structural framework and a high operating potential; these properties have enabled it to be widely studied as a stable and high-energy density cathode material for sodium-ion batteries (SIBs).1-4 In the present study, we designed a Na3V1.6Cr0.4(PO4)3/C (NVCrP@C) cathode by implanting Cr into the crystal structure of NVP and simultaneously coating the surface of NVP with carbon for realizing high power density SIBs. NVP is fabricated using a low-cost pyro synthesis technique with the advantage of self-carbon-coating and nano sized particles are gained through this facile technique. The substitution of Cr with vanadium in the NVP structure significantly enhanced the structural stability of the electrode while the uniform and thin carbon layer improved the electrical conductivity. Interestingly, the NVCrP@C cathode showed high electrochemical activities with multiple V3+/4+/5+ redox reactions triggered by Cr3+ substitution in a wide voltage range (2.5–4.1 V). Consequently, the NVCrP@C cathode delivered excellent cycling stability over 500 cycles even at 15 C-rate and power capability up to 70 C-rate.

References

Y. Cao, L. Xiao, W. Wang, D. Choi, Z. Nie, J. Yu, L. V. Saraf, Z. Yang and J. Liu, Mater., 2011, 23, 3155-3160.

M. Giot, L. C. Chapon, J. Androulakis, M. A. Green, P. G. Radaelli and A. Lappas, Rev. Lett., 2007, 99, 247211

M. H. Han, E. Gonzalo, G. Singh and T. Rojo, Energy Environ. Sci., 2015, 8, 81-102.

H. Liu, J. Xu, C. Ma and Y. S. Meng, Chem. Comm., 2015, 51, 4693-4696
(Digital Presentation) Long Cycle Life Li-Ion Batteries Using Solidified Gel Electrolyte Prepared Via in-Situ Crosslinking
Authors: Cluzeau Benoît , Dedryvere Remi , Dumont Erwan , Gillot Stephane , Jordy Christian , Pavlenko Ekaterina
Published: July 2022

Solid Polymer Electrolytes (SPEs) are promising candidates for all-solid-state lithium batteries. Light, flexible and non-flammable, they could overtake many limits of classical Li-ion batteries. Moreover, polymer electrolytes allow for the use of Li metal as negative electrode without safety issues of dendrites formation. But the current state-of-the-art on SPEs generally reports low ionic conductivity at room temperature (RT), poor lithium transport properties, and large interfacial resistance. All these limitations explain the difficulties of SPEs to be used in practical applications at RT.

Gel Polymer Electrolytes (GPEs), composed of a polymer matrix swelled by a liquid electrolyte, are a first step to approach solid state electrolytes. Preliminary results confirm that GPEs exhibit high ionic conductivity and good interfacial contact. In addition, preparation via in-situ polymerization is compatible with the conventional Li-ion fabrication equipment simplifying the battery assembly process.

A GPE based on poly(ethylene glycol diacrylate) (PEGDA) as polymer matrix was synthetized using in-situ thermal cross-linking. Coupled with a non-flammable liquid phase, this GPE shows good performance in terms of ionic conductivity, electrochemical stability and safety. The mechanical properties can be tuned by changing the polymer-to-liquid weight ratio. As a proof of its suitability for Li-ion batteries, NMC and graphite electrodes with high loading were used to prepare 100 mAh pouch cells. After studying polymer distribution in the electrode, electrochemical testing revealed a very good capacity retention (>80% after 350 cycles).

Figure 1
(Digital Presentation) High Energy Density Picoliter Zn-Air Batteries for Colloidal Robots and State Machines
Authors: Zhang Ge , Yang Jingfan , Strano Michael
Published: July 2022

The recent interest in microscopic autonomous systems, including microrobots, colloidal state machines and smart dust has created a need for microscale energy storage and harvesting. However, macroscopic materials for energy storage have noted incompatibilities with micro-fabrication techniques, creating significant challenges to realizing microscale energy systems. Herein, we photolithographically pattern a microscale Zn/Pt/SU-8 system to generate the highest energy density microbattery at the picoliter (10-12 L) scale. The device scavenges ambient or solution dissolved oxygen for a Zn oxidation reaction, achieving an energy density ranging from 760 to 1070 Wh L-1 at scales below 100 μm lateral and 2 μm thickness in size. More than 10,000 devices per wafer can be released into solution as functional colloids with energy stored onboard. Within a volume of only 2 pL each, these microbatteries can deliver open circuit voltages of 1.16 V with total energies ranging from 5.5 ± 0.3 to 7.7 ± 1.0 μJ and a maximum power near 2.7 nW. We demonstrate that such systems can reliably power a micron-sized memristor circuit, providing access to non-volatile memory. We also cycle power to drive the reversible bending of microscale bimorph actuators at 0.05 Hz for mechanical functions of colloidal robots. The high energy density, low volume and simple configuration promise the mass fabrication and adoption of such picoliter Zn-air batteries for micron-scale, colloidal robotics with autonomous functions.
Template-Free Reaction Networks Enable Predictive and Automated Analysis of Complex Electrochemical Reaction Cascades
Authors: Barter Daniel , Spotte-Smith Evan Walter Clark , Redkar Nikita S , Dwaraknath Shyam , Persson Kristin A. , Blau Samuel M
Published: July 2022

Chemical reaction networks (CRNs) are powerful tools for obtaining mechanistic insight into complex reactive processes. However, existing techniques rely heavily on chemical intuition and prior knowledge, limiting their applicability in domains like electrochemistry where reaction mechanisms or stable products are not well understood and where potential energy surface exploration is computationally intractable. Here we report new methods of CRN generation and analysis that overcome these limitations. By constructing CRNs using filters, rather than templates, we preserve species and reactions that are unintuitive but fundamentally reasonable for processes driven by an applied potential. The resulting massive CRNs can then be interrogating via stochastic methods, revealing thermodynamically bounded reaction pathways to species of interest and automatically identifying network products. We apply this methodology to study solid electrolyte interphase (SEI) formation in Li-ion batteries. Our methods automatically recover SEI products from the literature and predict previously unknown species; the predicted formation mechanisms to select products are then validated using first-principles calculations. This methodology enables the efficient de novo exploration of vast chemical spaces, with the potential for diverse applications across electrochemistry and photochemistry.
Impedance-Based, Multi-Physical DC-Performance-Model for a PEMFC Stack
Authors: Goosmann Tobias , Raab Sebastian , Oppek Philipp , Weber Andre , Ivers-Tiffee Ellen
Published: July 2022

Performance prediction for large-sized polymer electrolyte membrane fuel cell (PEMFC) stacks necessitates consideration of spatially deviating operating conditions on the nonlinear electrochemical behaviour. This interaction between operating conditions and electrochemistry is best described by complex CFD-models. But high computing power excludes stack and system modelling in real time applications.

We address this challenge by a multi-physical stack model, which couples (i) the non-linear electrochemistry within the cell, (ii) the fluid pressure drop along the gas channels and (iii) the thermal behaviour within the stack. The spatial resolution focusses on the most relevant directions and thus limits the computational effort. Simulation runtime is further reduced by modelling the electrochemical behaviour by a physico-chemically meaningful equivalent circuit model (ECM) [1], which relies on a data set of electrochemical impedance spectroscopy (EIS) measurements performed on incremental cells [2]. Individual impedance contributions are identified by the distribution of relaxation times (DRT). ECM model parameters are subsequently quantified by a CNLS-fitting procedure [3,4] and transferred to a nonlinear, zero-dimensional DC-performance-model. The magnitude of the modelled pressure depends on the gas flow within the channel and considers the change of gas composition, whereas the local gradients in current density cause gradients in released heat within the cell itself. This effect along the gas flow, the convection between fluids and solid parts of the stack (bipolar plates and cell) and the internal heat conduction between the solid control volumes are considered in the modelled thermal behaviour.

In this contribution a multi-physical stack model considering gradients in temperature, pressure and gas composition is presented. The interdisciplinary interactions and dependencies within the different physical domains, especially the influence of pressure and temperature on the non-linear electrochemical model, are shown. A concise validation based on measured data and conclusions for the possibilities of further applications as a system model will be discussed.

[1] D. Klotz et. al., ECS Transactions 25, pp. 1331-1340 (2009)

[2] M. Heinzmann et al., J. Power Sources 402, pp. 24-33 (2018).

[3] H. Schichlein et al., J. Appl. Electrochem. 32, pp. 875-882 (2002).

[4] S. Dierickx et al. Electrochimica Acta 355, 136764 (2020)
Smoothed Boundary Method Electrochemical Simulation Framework for Complex Electrode Microstructures
Authors: Malik Affan , Qu Danqi , Yu Hui-Chia
Published: July 2022

Battery and fuel cell electrodes possess highly complex microstructures: tortuous interparticle space, irregular particle surfaces, and various particle sizes. Additionally, coupled physical mechanisms, such as mass transport and electron transport, heat generation, and phase transformations, simultaneously occur during the electrode’s operations. All these combined complexity makes modeling electrochemical processes with explicit considerations of electrode microstructures very challenging. As such, electrode designs are still heavily relied on experimental trial-and-error methods even though modern computational resources have grown rapidly. Furthermore, experimental technologies have become very mature to reconstruct three-dimensional (3D) microstructures. The abundant microstructure data open a window for directly simulating the physical processes in complex microstructures. This talk will introduce an innovative simulation method using a continuous function to define complex microstructures. Since the irregular complex microstructure surfaces are implicitly described, this method no longer requires meshes conformal to the complex microstructures as in the conventional simulations. Thus, it allows us to simulate detailed electrochemical phenomena in complex electrode microstructures in an unprecedented pace with ease, especially for image-based, reconstructed microstructures. We will showcase several recent simulations to demonstrate the presented method, including phase transformations in porous graphite anode, hybrid electrodes, electrochemical impedance spectroscopy, and electrochemical processes in NMC-separator-graphite full-cell. The presented method is applicable to other electrochemical systems, and can be extended to include other physical mechanisms for further studying cycling-induced phenomena such as stress, heat, and Li-plating.

Figure 1
Selective Ion Sieving and Disorder in Membranes Constructed from Two-Dimensional Covalent Organic Frameworks
Authors: Parkinson Bruce Alan , Hoberg John , Li-Oakey Katie , Duong Phuoc
Published: July 2022

Two-dimensional covalent organic frameworks (2D-COFs) have been of increasing interest in the past decade due to their potentially ordered porous structures. One of the most common routes to these polymers relies on Schiff-base chemistry, i.e. the condensation reaction between a carbonyl and an amine. However, the judicious choice of these two building blocks is critical given that many COF forming reactions can lead to an inherent disorder if such a pathway is available. Examples of disorder in 2D-COFs due to both inherent growth mechanisms and reaction pathways will be given and their influence on ion sieving membranes will be discussed. A 2D-COF with negatively charged carboxylated pores, where disorder is minimized, has been shown to be highly charge and size selective for ion conductivity for a series of tetraalkyl ammonium cations. Progress on membranes for desalinization and small ion separations such as Li ion separation from brines using negatively charged, positively charged and zwitterion pores will also be presented.
(Keynote) Selective Transport of Ionic Species in Membranes - Effects of Specific Interactions and Nano-Morphology
Authors: Münchinger Andreas , Kreuer Klaus Dieter
Published: July 2022

Selective transport of specific ions is not only key to certain chemical and electrochemical applications, it also raises a number of interesting fundamental questions. For example, in a redox-flow battery, a membrane has to efficiently separate the electrochemically active ionic species (e.g. the different vanadium species present in anolyte and catholyte of a VRFB) while conducting other ionic species for mediating the electrochemical reactions. Fundamentally, selective transport is related to issues of ion uptake and ion mobility. There may be preferred uptake of certain ionic species while others may dominate ionic transport; under certain conditions, an anion exchange membrane (AEM) may even turn into a proton conductor.

This presentation provides insight into the effects membrane morphology and chemical interactions have on selective ion transport. Common thermodynamic considerations have been modified by including effects of ion solvation and the influence acid/base properties of the fixed ions have on counter-ion condensation. In addition, insights into the membrane’s nano-morphology allowed to identify sterical effects on ionic transport (ion-sieving).

With these sophistications, transport data are described in a quantitative way and guidelines are provided which may help to select or tailor membranes for particular applications requiring selective ion transport.
Modelling the Electrolyte Flow in the Tanks of Vanadium Redox Flow Batteries: A CFD Perspective
Authors: Prieto-Diaz Pablo Angel , Maurice Ange Anicet , Vera Marcos
Published: July 2022

Redox flow batteries are a promising technology for large-scale energy storage. The flow of the electrolyte in the tanks is a relevant factor for battery optimization that has been largely overlooked to date, with departures from perfect mixing associated with an effective capacity loss of the system. The flow in the tanks is driven by the competing effects of inertia and buoyancy, the former associated with the momentum flux of the discharging jet and the latter with the density changes suffered by the electrolyte as it passes through the cell because of the slight changes in temperature and state of charge (SoC). Three different flow regimes may be found in the system, each dominated by one effect or the other, or by both when they are comparable. All these phenomena are governed by the current intensity applied (I), the volumetric flow (q) and the properties of the vanadium electrolyte.

In particular, it is seen that an accurate description of the effect of the temperature and state of charge on the density and specific heat of the electrolytes is essential to compute the buoyancy induced flow and heat transfer taking place in the tanks. A parametric sweep is presented to show the impact of these dependences on the mixing process, which calls for the need of accurate experimental measurements of the variation of the physical properties of the electrolytes with their temperature and state of charge.

Our numerical simulations show that the electrolytes are never perfectly mixed, and that the homogeneity of the species concentration is strongly dependent on the operation conditions and on the tank design, with details of the inlet and outlet ducts being particularly relevant. Results on the charging and discharging operations, heating process and the rising of the state of charge in the cell are presented and discussed.

Acknowledgments

This work has been partially funded by the Agencia Estatal de Investigación (PID2019-106740RB-I00 and RTC-2017-5955-3/AEI/10.13039/501100011033), and by Grant IND2019/AMB-17273 of the Comunidad de Madrid.

Figure 1
Novel Anolyte Redox Active Organic Molecules for Non-Aqueous Redox Flow Batteries
Authors: Jesse Kate , Mukundan Rangachary , Maurya Sandip
Published: July 2022

Non-aqueous redox flow batteries (NARFBs) offer several advantages over traditional aqueous electrolyte-based redox flow batteries, such as higher cell voltage, potentially higher energy density, and flexible operating temperatures. However, the current aqueous chemistries use toxic metals such as Vanadium and Chromium and highly acidic and oxidative acid mixtures. The efforts to develop metal-ligand based chemistries to tap the benefits of NARFBs have met with mixed success and only V(acac)3 based symmetric NARFBs have shown potential for long term operations. Even so, the solubility of V(acac)3 in non-aqueous solvents is low to compete with their aqueous counterpart. Moreover, modification of V(acac)3 to enhance the solubility has resulted in poor redox cyclability. As a result, recent research trends have shifted from the development of Metal-ligand complexes to small redox-active organic molecules (ROMs), which could provide higher solubility. However, due to the developing field, a few ROMs have been reported as stable electron donors and acceptors in their oxidized and reduced states. Therefore, we have focused on developing highly soluble anolyte materials with stable redox states. This presentation will discuss the design principle, synthesis, and electrochemical analysis of novel anolyte ROMs. The additional information about the kinetics, bulk electrolysis, and the performance in the full cell will also be discussed.

Acknowledgement

This work is supported by Laboratory Directed Research & Development (20210680ECR), Los Alamos National Laboratory.
Fundamental Aspects of the Electron Transfer Processes in Non-Aqueous Redox Flow Batteries
Authors: Stracensky Thomas , Maurya Sandip , Mukundan Rangachary , Mukerjee Sanjeev
Published: July 2022

Redox flow batteries (RFBs) have garnered increasing attention for energy storage applications with non-aqueous RFBs offering several advantages such as larger voltage windows and the prospect of high energy densities. To increase the efficacy of non-aqueous RFBs, much effort has gone into the design of redox moieties that are highly soluble, cheaper, and robust, with desired electrochemical properties. To evaluate the capability of these redox moieties for RFB applications, the kinetics and thermodynamics of electron transfer events need to be understood. These insights could help towards rational design of redox moieties and to predict RFB performance. Techniques such as cyclic voltammetry and rotating disk electrode are commonly used to study the fundamental parameters of electron transfer process and thermodynamic properties of the redox moieties in both the neutral and charged states.

In this work, we investigate the effects of supporting electrolytes on the thermodynamics and kinetics of the redox moieties. Vanadium (III) acetylacetonate and iron complexes are the bipolar model redox moieties used as both negative and positive electrolyte in non-aqueous RFB applications.1 While many redox moieties are stable in the neutral state, it is during cycling that degradation of the complexes typically occurs. As shown previously, the supporting electrolyte composition plays a key role in the performance and stability of the redox species in RFBs.2 We found that ion pairing between the charged redox moieties and the supporting electrolyte resulted in lower diffusion coefficients, it also has a negative impact on the kinetics of charge transfer process. We propose that the observed ion pairing can explain the stabilizing effects of supporting electrolytes on redox moieties. The magnitude of this effect can be explained by hard soft acid base theory (HSAB) which can be further used to predict the extent of ionic interactions of the charged species in the RFB electrolytes.

Acknowledgements:

Los Alamos National Laboratory is operated by Triad, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy (Contract No. 89233218NCA000001). Authors would like to thank Dr. Imre Gyuk and financial support from the U.S. Department of Energy’s Office of Electricity for the publication of this work is gratefully acknowledged.

Sharma, G.A. Andrade, S. Maurya, I.A. Popov, E.R. Batista, B.L. Davis, R. Mukundan, N.C. Smythe, A.M. Tondreau, P. Yang, J.C. Gordon, Iron-iminopyridine complexes as charge carriers for non-aqueous redox flow battery applications, Energy Storage Mater., 37 (2021), pp. 576-586

Wei X, Xu W, Huang J, Zhang L, Walter E, Lawrence C, Vijayakumar M, Henderson WA, Liu T, Cosimbescu L, Li B, Sprenkle V, Wang W. “Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery” Angew Chem Int Ed Engl.
2015, 54 (30): 8684-7.
Investigating the Role of Temperature on the Performance of Vanadium Redox Flow Batteries Using a Steady Validated Unit-Cell Model
Authors: Muñoz Perales Vanesa , Berling Sabrina , Ibanez Santiago Enrique , Garcia - Quismondo Enrique , Palma Jesus , Vera Marcos
Published: July 2022

Redox Flow Batteries (RFBs) are an evolved electrochemical energy storage technology crucial for the transition into a renewable energy future. Mainstream adoption of RFBs is subject to reduction of the capital and operation costs. In that sense, of particular importance is the optimization of the electrochemical stack, which affects the overall efficiency of the battery. Several studies have investigated the importance of thermal effects on the performance of vanadium redox flow batteries through transient non-isothermal models [1-2]. However, due to the simplified assumptions made by these authors some important temperature-dependent features are not included. Therefore, reliable and validated continuum models are also crucial to study the impact of the system temperature on all the fundamental physics in the electrochemical cells as well as to find the key aspects to optimize the stack.

In this work, we present a 2D stationary model of a vanadium redox flow battery cell with a comprehensive and updated multiphysics description. The model was validated at a constant temperature of 25 ºC by polarization, conductivity, and open circuit voltage measurements. In a second step, the temperature was also included as a key operating variable in the model. Electrolyte properties, electrochemical rate constants, and H2SO4 dissociation equilibrium were described as a function of temperature as well as the state of charge (SoC) and the total vanadium concentration. The model is currently being validated through a second experimental campaign (see Fig. 1) conducted inside a climatic chamber imitating different environmental scenarios. The model can be used to explore the relevance of each phenomenon or element in the electrochemical stack and the influence of the operating conditions on them, e.g. temperature, state of charge and volumetric flow rate. By using the proposed model, we can elucidate the best temperature strategy to increase the performance of vanadium redox flow batteries in diverse operating scenarios.

Figure 1. Open circuit voltage – SoC relation at different operating temperatures.

References

Al-Fetlawi, A.A. Shah, F.C. Walsh, Electrochimica Acta, 55, 78-89 (2009).

Tang, S. Ting, J. Bao, M. Skyllas-Kazacos, Journal of Power Sources, 203, 165-176 (2012).

Acknowledgments

This work has been partially funded by the Agencia Estatal de Investigación (PID2019-106740RB-I00 and RTC-2017-5955-3/AEI/10.13039/501100011033).

Figure 1
(Keynote, Digital Presentation) An Electrochemical Potential Perspective on Exchange Current Density and Work Function for Hydrogen Evolution Reaction (HER)
Authors: Parr Daniel , Dadallagei Kasun Saweendra Rathnatunga , Debie Sidney , Coduto Joshua Richard , Haas Christian D , Leddy Johna
Published: July 2022

In 1972, Trasatti compiled the exchange current densities j0
and work functions 𝚽 for the hydrogen evolution reaction (HER) on 31 polycrystalline metals at pH 0. Exchange current density measures the HER rate and the work function measures the energy required to remove an electron from the surface of the metal to a point outside the metal. Trasatti showed a plot of log j0
vs 𝚽 linear for the so called d metals and for the sp metals. The slopes are statistically the same for the d and sp metals (6.44 and 6.6 excludes Hg) but the intercepts differ (-35.4 and -38).

Here, a thermodynamic specification for the slope of log j0
versus 𝚽 is suggested as 𝛂F/RT, where 𝛂 is the transfer coefficient for heterogeneous electron transfer.

Electrochemical potentials for species i in phase j have been used to derive the rates of heterogeneous electron transfer within a transition state context for Butler Volmer kinetics (Bard and Faulkner).

The standard chemical potential, activity, and ion charge for species i are 𝝁i
0,j, ai
j, and zi is the electrical potential is 𝝓j.

Extrapolation of the electrochemical potential to include 𝚽 and derive a rate expression for j0
yield:

The electrode potential and the work function group into a common term.

The slope of log j0
versus 𝚽 as 𝛂F/RT.

An explanation of how Pt with the highest energetic cost to remove an electron 𝚽 yields the highest log j0
is presented.

At 25 oC, F/RT = (0.05916 V)-1. Within the electrochemical potential model for log j0
versus 𝚽, the slopes of 6.44 and 6.6 for the d and sp metals at room temperature yield 𝛂 of 0.381 and 0.39. Across 30 metals, 𝛂 is estimated the same. The value of 0.4 is common in measurements of 𝛂 found for the potential dependent term in Butler Volmer kinetics.

References

Trasatti, S. Work Function, Electronegativity, and Electrochemical Behavior of Metals. III. Electrolytic Hydrogen Evolution in Acid Solution. Electroanalytical Chemistry and Interfacial Electrochemistry 39, 163-184 (1972).

A.J. Bard and L. R. Faulkner, Electrochemical Methods, 1980, wiley and Sons, Chapter 2.

Acknowledgments

This work was supported by the National Science Foundation and the Army Research Office. The University of Iowa Obermann Center for Advanced Studies is acknowledged.