bluuebunny/crossref_metadata_2025 huggingface dataset:
Apple Pectin Based Hydrogel Electrolyte for Energy Storage Application
Authors: Chelfouh Nora , Coquil Gaël , Rousselot Steeve , Briqueleur Elsa , Foran Gabrielle , Dollé Mickaël
Published: July 2022

With the increase of portable power sources demand, new technologies, e.g. wearable and flexible electronics, are projected to generate $1.25 billion market by 2022.[1] New storage energy devices are more than ever in demand which requires new specifications in order to be used in those future applications. To achieve this development, we have to minimize the environmental impact in the whole battery life cycle, from conception to degradation of the system, and reduce production costs. Polymer hydrogel electrolyte are one of the promising alternative for processing new flexible batteries.[2] A great hydrogel electrolyte should promise excellent ionic transport pathways and sufficient mechanical strength, not to cause short-circuits. As a matter of fact, hydrogel electrolytes are well-known for their good ionic conductivity. Nevertheless, the original polymers used in these systems don’t take into account the cost of the environmental impact and safety due to the processing or biodegradability of those hydrogels.[3]

In this study, we report a new hydrogel-based electrolyte material made by apple pectin. This presentation will mainly focus on the interactions between pectin functional groups, water and ions using solid NMR spectroscopy. Thermal properties will be discussed based on differential scanning calorimetry analysis. Electrical and electrochemical characterisctics obtained by electrochemical impedance spectroscopy, galvanostatic cycling and cyclic voltametry will demonstrate the applicability of such hydrogel electrolyte.

This study could promote a great innovation in the energy storage field, by recycling one of apple peel’s component (which is the main waste in preserves manufacturing[4]) into a hydrogel electrolyte.

References

[1] N. R. C. Canada in Environmentally friendly printed batteries, Vol. Boucherville, Quebec, 2021.

[2] C. Y. Chan, Z. Wang, H. Jia, P. F. Ng, L. Chow and B. Fei, Journal of Materials Chemistry A
2021, 9, 2043-2069.

[3] Y. Huang, M. Zhong, F. Shi, X. Liu, Z. Tang, Y. Wang, Y. Huang, H. Hou, X. Xie and C. Zhi, Angewandte Chemie International Edition
2017, 56, 9141-9145.

[4] B. S. Virk and D. S. Sogi, International Journal of Food Properties
2004, 7, 693-703.
Cation Size Effect on Oxygen Reduction Reaction in Aprotic Electrolytes
Authors: Fernández Vidal Julia , Galloway Thomas , Attard Gary , Hardwick Laurence J.
Published: July 2022

The most important cathodic process in alkali metal-air (M-O2) batteries is the electrocatalytic oxygen reduction reaction (ORR) typically forming superoxide (MO2), and peroxide (M2O2).1 Cation size in aqueous solvents have been demonstrated to affect the ORR activity due to the cation hydration energy.2 However, within aprotic electrolytes, the reaction mechanisms and the activity of ORR with respect to cation size remains undetermined.

Traditionally, electrochemistry has been involved in the analysis of the reaction mechanisms of ORR. Nonetheless, this technique by itself is not suitable to identify intermediaries and products of the redox reactions taking place at the electrochemical interface. The combination of cyclic voltammetry with in situ Raman spectroscopy provide the opportunity to study and develop a fundamental understanding of the ORR under potential control, accessing reaction pathways and relating them directly to surface structure.3 In this sense, the breakthrough of Shell-Isolated Nanoparticles for Enhanced Raman Spectroscopy (SHINERS)4,5 is noteworthy. SHINERS is a non-destructive, powerful technique for surface analysis that has been demonstrated to provide SERS effect even in the absence of intrinsic roughness and without requiring Au, Ag or Cu to be used as working electrodes.3,5

In this work, electrochemical measurements and SHINERS are utilised to study the effect of cation upon electrified interfaces during ORR.

Zhang, J., Zhang, X.-G., Dong, J.-C., Radjenovic, P. M., Young, D. J., Yao, J.-L., Yuan, Y.-X., Tian, Z.-Q. & Li, J.-F. Real-Time Monitoring of Surface Effects on the Oxygen Reduction Reaction Mechanism for Aprotic Na–O2 Batteries. J. Am. Chem. Soc.
143, 20049–20054 (2021).

Kumeda, T., Tajiri, H., Sakata, O., Hoshi, N. & Nakamura, M. Effect of hydrophobic cations on the oxygen reduction reaction on single‒crystal platinum electrodes. Nat. Commun.
9, 1–7 (2018).

Guan, S., Attard, G. A. & Wain, A. J. Observation of Substituent Effects in the Electrochemical Adsorption and Hydrogenation of Alkynes on Pt{hkl} Using SHINERS. ACS Catal.
10, 10999–11010 (2020).

Li, J. F., Huang, Y. F., Ding, Y., Yang, Z. L., Li, S. B., Zhou, X. S., Fan, F. R., Zhang, W., Zhou, Z. Y., Wu, D. Y., Ren, B., Wang, Z. L. & Tian, Z. Q. Shell-isolated nanoparticle-enhanced Raman spectroscopy. Nature
464, 392–395 (2010).

Galloway, T. A., Dong, J.-C., Li, J.-F., Attard, G. & Hardwick, L. J. Oxygen reactions on Pt{hkl} in a non-aqueous Na+ electrolyte: site selective stabilisation of a sodium peroxy species. Chem. Sci.
10, 2956–2964 (2019).
Calculations of pH-Dependent Redox Potentials for Proton-Coupled Electron Transfer Reactions
Authors: de Silva Piotr
Published: July 2022

We will present a computational protocol that combines density functional theory (DFT) and cheminformatics approaches to predict redox potentials of organic molecules as a function of the pH of the aqueous solution.[1] The methodology is based on an improved version of the Alberty-Legendre transform to account for varying protonation states of the redox reaction products at different pH values. Our approach circumvents the known problems with the use of DFT calculations and implicit solvation models for highly charged anions. To validate the protocol, we use a consistent set of quinones which can undergo up to two-electron two-proton redox reaction. As the reference we use the experimental redox potentials measured at pH 0, 7, and 13.[2] We demonstrate that with the proposed methodology we can achieve the MAE=0.144 V and MSE=-0.016 V at pH=13.

[1] Fornari, R.P.; de Silva, P. A Computational Protocol Combining DFT and Cheminformatics for Prediction of pH-Dependent Redox Potentials. Molecules 2021, 26, 3978.

[2] Wedege, K.; Dražević, E.; Konya, D.; Bentien, A. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility. Sci. Rep. 2016, 6, 39101.
Simulating Scanning Electrochemical Microscopy Images of Arbitrarily Shaped Reactive Sites without a Site-Specific Model
Authors: Leslie Nathaniel , Mauzeroll Janine
Published: July 2022

Scanning electrochemical microscopy (SECM) yields two-dimensional electrochemical images when the current at a microelectrode is recorded as it moves above a surface generating redox species. As SECM images are often systematically compared to microstructure features obtained by electron microscopy there is a clear need to find ways to integrate electron microscopy images into SECM image simulations.

Recently, finite element method simulations of sites where electrochemical reactions take place is employed to evaluate reactive feature size.[1] Current models move the microelectrode or the reacting surface, continuously changing the geometry of the simulation and thus requiring re-meshing, which increases the computation time.

We present a modeling approach by which SECM images of arbitrarily-shaped reactive sites can be simulated using a grid of pixels that can be turned ‘on’ and ‘off’ using COMSOL® multiphysics. Specifically, COMSOL®’s Java API is used to change the selection of pixels that are turned ‘on’ to simulate the movement of the electrode without changing the geometry of the simulation. The mesh can be re-used for each data-point in the image, dramatically reducing the time needed to simulate SECM images. This work also presents a mostly automated workflow for using an electron microscopy image of a reactive site to determine which pixels should be turned ‘on’ and fitting the kinetics at these pixels by simulating their SECM image.

[1] L. I. Stephens, N. A. Payne, S. A. Skaanvik, D. Polcari, M. Geissler, J. Mauzeroll, Evaluating the Use of Edge Detection in Extracting Feature Size from Scanning Electrochemical Microscopy Images. Analytical Chemistry
2019, 91, 3944-3950.
(Invited) Modelling and Simulation for the Search for New Active Materials for Redox Flow Batteries - Results of the International Project Sonar
Authors: Noack Jens , Baudrin Emmanuel , Fornari Rocco , Franco Alejandro A. , Gerlach Daniel , Guan Xinjie , Hamaekers Jan , Maaß Astrid , Menictas Chris , Mourouga Gael , Nirschl Hermann , Roznyatovskaya Nataliya , Schaerer Roman , Schumacher Jürgen , de Silva Piotr , Skyllas-Kazacos Maria , Wlodarczyk Jakub , Wolf Amadeus , Yu Jia
Published: July 2022

Due to the characteristics of flow batteries, this technology is ideally suited for low-cost storage in the range of a few hours and thus for load balancing as stationary storage in grids with high amounts of renewable energy [1]. Today, a large number of different active materials for flow batteries are known, although only a few have been commercialised [2]. Basically, the energy supply and thus also the required storage should be sustainable, i.e. not cause resource problems and not be harmful to humans and the environment. A potential for a huge range of possibilities is offered by organic active materials, which should be used especially in aqueous solutions. Due to the immense possibilities, classical synthesis and testing is extremely lengthy and costly. An alternative can be model-based high-throughput screening, where by simulating the properties of active materials in the electrolyte and the battery itself, computer-based simulations can be used to conduct the search.

The SONAR project is an EU-funded project in which 7 different institutions from the EU, Switzerland and Australia are developing a high-throughput screening method capable of finding new active materials for redox flow batteries. The principle is a serial coupling of different size scales, combined with molecule generation and machine learning. The chemical structure of a candidate is generated by a molecule generator and then its atomistic properties, kinetics, side reactions and cell properties are iteratively calculated with exclusion criteria.

In this talk we will give an overview of 2 years of research in this project in the areas of machine learning for high throughput screening, DFT based quantum mechanics modelling, kinetics Monte Carlo methods for meso-scale, 0D cell modelling, 3D cell modelling, stack modelling and techno-economics.

[1] B. Dunn, H. Kamath, J.-M. Tarascon, Science 2011, 334, 928–935.

[2] J. Noack, N. Roznyatovskaya, T. Herr, P. Fischer, Angew. Chem. Int. Ed. 2015, 54, 9776–9809.

Figure 1
Modeling Solvation Thermodynamics in Molten Salts with Quasichemical Theory and Ab Initio-Accurate Deep Learning-Accelerated Simulations
Authors: Lam Stephen , Shi Yu , Beck Thomas
Published: July 2022

Molten salts are a promising class of ionic liquids used in advanced energy applications including next-generation nuclear reactors, batteries, and solar thermal energy storage. In these applications, understanding corrosion processes and predicting phase behavior remains a critical challenge. This requires accurate prediction of the solvation thermodynamics of ionic species in a variety of chemical and configurational states. In this work, we fundamentally address these challenges by combining quasichemical theory (QCT), ab initio simulation with density functional theory (DFT), and neural network interatomic potentials (NNIP) to accurately predict the solvation free energy of solute ions in molten salt. Ab initio data is used to train neural networks that learn the environment-dependent atomic forces and energies. This enables acceleration of atomistic simulation by more than three orders of magnitude. Using chemically accurate and highly efficient neural network-based molecular simulations, we perform free energy calculations within the QCT framework. Namely, QCT provides an exact partitioning of the free energy that includes contributions from 1) formation of a cavity in solution, 2) insertion of a solute ion into the cavity, and 3) relaxation of the cavity surrounding the solute ion. This requires simulations in timescales totaling tens of nanoseconds. As such, using AIMD alone is impractical for exploring a wide range of solutes, compositions, and thermodynamic conditions. In this work, we show that the NNIPs can accurately predict molten salt thermodynamics and local coordination structures. We provide a demonstration of the combined methods (DFT-NNIP-QCT) on molten NaCl, in which we obtain the total excess potentials of Na+ and Cl- ions, and perform corrections to errors in electrostatic energy caused by finite size of the simulation cell. The calculated excess chemical potential for Na+/Cl− was predicted to be -161.7±10.6 kcal/mol, which is consistent with previous calculations and an experimental value of -163.5 kcal/mol from thermochemical tables. These results provide initial validation of the methods for predicting excess chemical potentials, which can be directly exploited for the determination of solute chemistry, and the solubility of dissolved gases and metallic ions in molten salts. This provides motivation for the use of these methods to understanding solute chemistry in a wide range of molten salt systems in advanced energy applications.
Effect of Concentration-Dependent Electrochemical Kinetics in the Modeling of Electrolytic Neutral Pickling in Stainless Steel
Authors: Bossio Castro Alvaro , Blommaert Maarten , Gielen Ruben , Fransaer Jan , Baelmans Martine
Published: July 2022

The electrolytic neutral pickling is a process used in the stainless steel industry to remove the oxide layer formed during annealing. In this process the stainless steel strip is pulled through a tank containing a sodium sulfate solution and a set of alternating electrodes, which indirectly polarize the strip surface and cause oxide dissolution under the influence of an electric current. State-of-the-art models describing this process assume concentration-independent electrochemical kinetics, which leads to the conclusion that homogeneous chemical reactions have a negligible influence on the final current density distribution. The present work revisits these conclusions by assessing the impact of concentration-dependent Butler-Volmer kinetics. Concentration distributions within the diffusion layer are estimated using a reduced boundary layer model for the ionic species at each electrode surface, each of these concentrations being two-way coupled with the electric potential in the bulk. Finally, the effects of different electrolyte compositions, homogenous chemical reactions, and flow conditions on the current density at the electrode surfaces are evaluated and discussed.
Electrochemical Birch Reduction: A Molecular-Level Venture into the Solvation Structure at the Electrode Interface
Authors: Abbaspourtamijani Ali , Gu Chaoxuan , Wu Qisheng , Qi Yue
Published: July 2022

Although selective hydrogenation of aromatics through Birch reduction has long been at the heart of synthetic organic chemistry, its various proposed procedures suffer from monumental challenges. The optimized design of salt, solvent, and additives along with a sacrificial anode material has enabled the recent success of Electrochemically driven Birch reduction (E-Birch) reactions, which are procedurally convenient, safe, and sustainable1. The E-Birch reactions are premised upon the concepts applied in Li-ion battery research regarding the surface protection layer formation, also referred as the solid electrolyte interphase (SEI). However, the impacts of these constituents on the surface layer formation in E-Birch reactions is largely unknown. In this study, we have employed a combination of molecular dynamics (MD) simulations and density functional theory (DFT) calculations to provide insights into the liquid structure and the interactions of these constituents, both in bulk of the solution and at the electrode surface. Specifically, an optimal electrolyte design of LiBr salt in tetrahydrofuran (THF) solvent, with 1,3-dimethylurea (DMU) as the proton donor, and tris(pyrrolidino)phosphoramide (TPPA), as surface protector, has been studied as it promoted high yields of 1,4-diene formation from several aromatic-ring containing molecules with a variety of functional groups. We have found that THF, DMU, and TPPA are all present in the Li+ solvation sheath at the bulk of the solution and at the electrode surface. Since the surface layer is formed by the reduction reactions of solution, the reduction voltage was computed for representative solvation structures. It was found that the reduction voltage and reduction process of THF, DMU, and TPPA were altered by the Li+ coordination and are therefore sensitive to the liquid solution structures. In addition, we have demonstrated that the species in the solvation shell can undergo bond breaking events, which lead to protection layer formation at the electrode surface. The role of salt, solvent, additives, and sacrificial anodes in altering the solution structure and reduction reactions was further discussed.

References

Peters Byron, K.; Rodriguez Kevin, X.; Reisberg Solomon, H.; Beil Sebastian, B.; Hickey David, P.; Kawamata, Y.; Collins, M.; Starr, J.; Chen, L.; Udyavara, S.; Klunder, K.; Gorey Timothy, J.; Anderson Scott, L.; Neurock, M.; Minteer Shelley, D.; Baran Phil, S., Scalable and safe synthetic organic electroreduction inspired by Li-ion battery chemistry. Science 2019, 363 (6429), 838-845.
Optimization of Porosity Distribution in Gas Diffusion Electrodes for CO2 Electrolysis
Authors: Ehlinger Victoria Marie , Roy Thomas , King Alex , Baker Sarah , Duoss Eric B , Weber Adam Z. , Beck Victor A
Published: July 2022

The criteria dictating the performance of gas diffusion electrodes (GDEs) for CO2 electrolysis are not well understood, due to the complex and highly coupled relationships of the underlying physical and chemical phenomena. In addition, a number of key performance indicators (KPIs) have been identified (e.g., Faradaic efficiency, reaction selectivity, single-pass conversion, and productivity), and optimizing for any single metric often leads to inherent tradeoffs. Consequently, much recent work has focused on understanding how operational and architectural parameters control GDE performance. The porous catalyst supports and diffusion media in these devices are critical components as they mediate the transport and reactive processes. The microstructure of these components influences the balance between the electrochemical surface area, which dictates CO2 consumption, and mass transfer of the aqueous and gaseous species. Traditional porous media is often spatially homogeneous and provides limited opportunity to tailor this balance. In contrast, novel advanced manufacturing methods have now enabled researchers to create electrodes with variable porosity that can be tuned for optimal performance. To explore the impact of locally altering the porous media structure, we leverage previous modeling work by Weng et al. to allow for spatially varying porosity. Further, we couple the forward simulation to adjoint based optimization algorithms to determine optimal porosity distribution in the diffusion media and catalyst layer of a GDE. The cost functions for the optimization are derived from the previously mentioned KPIs. Finally, the performance of the resultant spatially varying porosity GDEs is compared to the performance of homogenous porosity GDEs, and we identify key features of the porosity distribution leading to improved performance.

Weng, Lien-Chun, Alexis T. Bell, and Adam Z. Weber. "Modeling gas-diffusion electrodes for CO2 reduction." Physical Chemistry Chemical Physics 20.25 (2018): 16973-16984.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

LLNL-ABS-830082
Understanding the Onset of Surface Degradation in LiNiO2 Cathodes
Authors: Li Xinhao , Wang Qian , Guo Haoyue , Artrith Nongnuch , Urban Alexander
Published: July 2022

Nickel-based layered oxides offer an attractive platform for the development of energy-dense cobalt-free cathodes for lithium-ion batteries but suffer from degradation via oxygen gas release during electrochemical cycling. While such degradation has previously been characterized phenomenologically with experiments, an atomic-scale understanding of the reactions that take place at the cathode surface has been lacking. Here, we discuss a first-principles methodology that we developed for the prediction of the surface reconstructions of intercalation electrode particles as a function of the temperature and state of charge. We report the surface phase diagrams of the LiNiO2(001) and (104) surfaces and identify surface structures that are likely visited during the first charge and discharge. Our calculations indicate that both surfaces experience oxygen loss during the first charge, resulting in irreversible changes to the surface structures. We identify specific reasons why Ni aggravates surface degradation and discuss possible remedies.

Figure 1
Flexible Laser-Patterned Carbon Coatings for Sensing and Energy Applications
Authors: Hepp Marco , Derr Katharina , Butz Benjamin , Wang Huize , Jimenez-Calvo Pablo , Strauss Volker
Published: July 2022

Fabricating electronic devices from natural, renewable resources has been a common goal in engineering and materials science for many years. In this regard, carbon-based coatings are of significance due to high availability of the raw materials and their environmental degradability. Carbonized materials and composites thereof have been proven as promising candidates for a wide range of future applications in flexible electronics, optoelectronics, energy storage or catalytic systems [1]. On the industrial scale, however, their application is inhibited by tedious and expensive preparation processes and a lack of control over the processing and material parameters.

A promising tool to tackle that challenge is carbon laser-pattering (CLaP) allowing for the defined and site-selective synthesis of functional carbon-based materials for flexible on-chip applications [2]. Versatile inks, based on naturally occurring (molecular) starting materials are used to produce films, which are carbonized with a CO2-laser to obtain functional patterns of conductive porous carbon networks [3]. By chemical and physical fine-tuning of the laser patterned carbons (LP-C), we developed high-performance flexible resistive chemical and mechanical sensors. Their properties make them applicable in many fields e.g., robotics, bionics and even health monitoring.

In this contribution, we present both, the material’s synthesis and tailored properties as well as in-depth microscopic and spectroscopic cross-sectional analyses of such coatings by advanced transmission electron microscopy, which provide unprecedented insights into the microstructure and local chemistry/bonding of laser-patterned carbon [4]. In that regard, we discuss the challenging cross-sectional preparation of such porous and sensitive structures by advanced ultramicrotomy. The gained insights in structure formation and local functionality pave the way for the utilization of alternative fast, large-scale carbonization methods such as rapid thermal annealing.

[1] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, M. C. Hersam, Chem. Soc. Rev. 2013, 42, 2824–2860.

[2] R. Ye, D. K. James, J. M. Tour, Adv. Mater. 2019, 31, 1803621.

[3] S. Delacroix, H. Wang, T. Heil, V. Strauss, Adv. Electron. Mater. 2020, 6, 2000463.

[4] M. Hepp, H. Wang, K. Derr, S. Delacroix, S. Ronneberger, F. Loeffler, B. Butz, V. Strauss, NPJ Flex. Electron. 2021, accepted for publication
(Digital Presentation) Novel Porous Functionalized Mwcnts-TiO2/g-C3N4 heterostructure Modified Screen Printed Electrode for a Rapid Enzyme-Free Detection of Uric Acid in Human Urine
Authors: Sundeep Dola , K Varadharaj Eswaramoorthy
Published: July 2022

Porous heterostructures gained wide appreciation for their escalated sensing performance in electrochemical society. In the present work, we report the porous functionalized MWCNTS-TiO2/g-C3N4 (f-MWTGCN) heterostructure modified screen-printed electrode for the detection of uric acid in human urea samples. The f-MWTGCN are synthesized via a two-step combination process by hydrothermal-assisted ultrasonication construction. The fabricated powders are subjected to X-Ray diffraction to identify the size, structure, dislocation densities, and micro strain. The morphological studies are performed by the FESEM and HRTEM analysis to identify the confinement of heterostructures. The required chemical analysis was obtained from the FTIR and Raman studies and substantiated the qualitative and quantitative vibrational modes. The obtained highly porous ultrafine powders are drop cast on the screen-printed electrode to modify the working electrode to achieve super ultrafast sensing. Functionalization of MWCNTs facilitated the carbon to attain hydroxyl, carboxyl, and carbonyl functional groups which assisted in the rapid detection of uric acid. The reproducibility and stability of the electrode were evaluated by the fifteen repeated cyclic voltammetry responses to 0.1M uric acid. The developed sensors showcased a detection of Limit (DoL) of 1.17 µM and sensitivity of 98.1 nA µM-1 with a range of two to three seconds. The utilization of the developed heterostructure for modifying screen-printed electrodes and sensing uric acid is a unique and novel approach. Thus, the fabricated highly stable sensor may be utilized as the uric acid sensor in biomedical applications.

Keywords: Porous, Heterostructures, Functionalized MWCNTS, Reproducibility, and Hydrothermal.
(Keynote) Molecular Engineering Strategies for Symmetric Aqueous Organic Redox Flow Batteries
Authors: de Silva Piotr
Published: July 2022

In this contribution we use electronic structure calculations to reveal structure-property relationships for symmetric aqueous organic redox flow battery (RFB) materials. Unlike normal asymmetric RFBs, the symmetric ones are based on bipolar electrolytes that exist in at least three oxidation states and can undergo a minimum of two distinct redox processes. We compute from first principles the redox potentials of selected electrolytes based on quinone, pyrazine, and pyridazine redox-active moieties.[1] The objective is to understand how the interaction between the redox units affects the potentials and solvation energies. We find that electronic interaction between redox units and intramolecular hydrogen bonding can be exploited to tune the difference between the redox potentials, i.e., the theoretical voltage of the battery. The redox potentials can be further fine-tuned in either direction by adding substituents. Starting from these observations, we formulate a set of rules that will help in finding improved electrolytes for symmetric RFBs.

[1] R. P. Fornari, M. Mesta, J. Hjelm, T. Vegge, P. de Silva, “Molecular Engineering Strategies for Symmetric Aqueous Organic Redox Flow Batteries”, ACS Materials Lett.
2020, 2, 3, 239–246.
A Critical Approach to Multi-Electron Materials for High Energy Density Non-Aqueous Redox Flow Batteries
Authors: Daub Nicolas
Published: July 2022

Redox flow batteries (RFBs) are very promising storage systems in the transition towards renewable energy sources. They can be broadly classified in aqueous and non-aqueous systems. Last-named operate with organic solvents, which allow for a much broader potential window (up to three times higher) compared to water. Combination of organic solvents with organic redox active materials could pave the way for all carbon-based RFBs with superior energy densities compared to aqueous systems.

In this contribution, newly developed organic electrolytes will be presented, focusing on their performance as RFB materials in acetonitrile with quaternary ammonium electrolyte salts. To push the limits of energy density, we investigated multi-electron reduction and oxidation reactions on a single molecule.

As catholyte, tetrathiafulvalene (TTF) as a core structure was used. The unsubstituted TTF exhibits two reversible oxidation events (-0.04 and +0.34 V vs Fc/Fc+) but a poor solubility in acetonitrile. To optimize this and to achieve a higher oxidation potential a series of molecules with different side chains was synthesized. The resulting solubilities led to volumetric capacities of up to 71 Ah/L for the newly designed compounds. Electrochemical cycling stability was evaluated in bulk electrolysis, UV-Vis-NIR and flow cycling experiments.

Current state-of-the-art anolytes based on N-methylphthalimide compounds exhibit one reversible reduction pair at a desirable low reduction potential (-1.87 V vs Fc/Fc+) and good cycling stability in bulk electrolysis experiments.[1] Expanding on this structure, new derivatives with one or two additional functional imide groups per phthalimide core were synthesized. Consequently, molecules with a single (-1.87 V vs Fc/Fc+), double (-1.26 and -1.88 V vs Fc/Fc+) and triple reduction event (-1.02, -1.65 and -2.37 V vs Fc/Fc+) can be obtained. To optimize their solubility in acetonitrile, a series of molecules with different side chains was synthesized for each of the three core structures. Determination of the solubility led to volumetric capacities of up to 66 Ah/L for the newly developed compounds. Additionally, we tested the electrochemical cycling stability in bulk electrolysis, UV-Vis-NIR, coin cell and flow cycling experiments. In the final flow battery, a high energy density of 24 Wh/L was achieved (at 1 M of transferred electrons).[2]

All of this led to a critical comparison between the different molecular designs, cumulating in design rules that will influence future designs of the organic redox active compounds for organic RFBs.

[1] Wei, X.; Duan, W.; Huang, J.; Zhang, L.; Li, B.; Reed, D.; Xu, W.; Sprenkle, V.; Wang, W. A High-Current, Stable Nonaqueous Organic Redox Flow Battery. ACS Energy Lett.
2016, 1, 705−711

[2] Daub, N.; Janssen, R. A. J.; Hendriks, K. H. Imide-Based Multielectron Anolytes as High-Performance Materials in Nonaqueous Redox Flow Batteries. ACS Appl. Energy Mater.
2021, 4, 9, 9248–9257
Dicationic Heteroaryl Pyridinium As a Highly Stable, Soluble, and Crossover-Resistant Anolyte for Nonaqueous Redox Flow Batteries
Authors: Ahn Seongmo , Jang Jin Hyeok , Joo Jung Min , Byon Hye Ryung
Published: July 2022

Recently, redox flow batteries (RFBs) have emerged as one of the promising candidates for safe and economical grid-scale energy storage system (ESS) that store the intermittent energies such as wind or solar energy. Unlike the conventional aqueous vanadium RFBs, the design of new molecules in nonaqueous RFB (NRFB) has been in the spotlight for the high energy density, cycling stability, and low cost. Among the redox active materials, in particular, organic molecule has various structures through functionalization, and thus its redox potential, solubility, and chemical stability can be controlled. However, there are only a few viable negative-side redox electrolyte, called a negolyte (or anolyte) to date, and even the reported negolytes have suffered from low solubility and stability, and severe crossover problems for long-term cycling.

Here we show the systematic design strategies for pyridinium-based organic redox molecule to enhance the its stability and solubility and suppress the crossover rate for NRFB. A benzo[d]thiazole ring, which provides an electron-withdrawing effect, was introduced at the C4 position of pyridinium core by Pd catalyzed C-H arylation. The addition of the π-conjugation system to the pyridinium redox core was key to enhance chemical and electrochemical stability, resulting in negatively low redox potential of -1.19 ~ 1.21 V vs. Fc/Fc+. The solubility of pyridinium derivatives was significantly enhanced from 0.26 M to 1.00 M in acetonitrile by simple anion exchange from tetrafluoroborate (BF4
-) or hexafluorophosphate (PF6
-) anion to bis(trifluoromethanesulfonyl)imide (TFSI-) anion. Moreover, exchanging the functional group on N of pyridinium from methyl group to cationic 3-(trimethylammonio)propyl (TMAP) group suppressed the crossover rate with an anion-exchange membrane in the NRFB. 4-(benzo[d]thaizol-2-yl)-1-(3-(trimethylammonio)propyl)pyridin-1-ium (TMAP-BTP) led to electrochemical stability in symmetric cell, showing a capacity decay rate of 0.0083% per cycle. Contrary to the results of only 60% capacity retention after 100 cycle in full cell with 4-(benzo[d]thaizol-2-yl)-1-methylpyridin-1-ium (BTP) as negolyte, in the case of full cell with TMAP-BTP as negolyte, the capacity retention was significantly increased, showing 89.8 % after 100 cycle, which is ~0.08% capacity decay rate per cycle. In this presentation, I will demonstrate the more detailed design strategies, cycling performances, and electrolyte analysis. (Figure
1).1

References

Ahn, J. H. Jang, J. Kang, M. Na, J. Seo, V. Singh, J. M. Joo and H. R. Byon, ACS Energy Lett., 6, 3390 (2021).

Figure 1
Understanding Capacity Fade in Organic Redox-Flow Batteries Using Uncertainty Quantification Techniques and Zero-Dimensional Modeling
Authors: Modak Sanat Vibhas , Shen Wanggang , Owhoso Fiki G , Huan Xun
Published: July 2022

We introduce the use of Bayesian uncertainty quantification to provide data-informed assessments of the probability of different hypotheses of reactant decay, and to estimate reactant decay parameters from experimental data with quantified uncertainty. As a case study, we use these techniques to extract rate constants describing the nucleophilic attack of quinone-based RFB reactants by water, as measured using in operando ultraviolet-visible spectrophotometry. We then introduce a zero-dimensional electrochemical flow cell model3 which can simulate capacity fade given a reactant decay mechanism and associated parameters, and the cycling protocol. This work has the potential to shed light on the relationship between capacity fade and reactant decay in various organic RFB chemistries, and to enable prediction of the lifetimes of commercial-scale RFBs.

(1) Brushett, F. R.; Aziz, M. J.; Rodby, K. E. On Lifetime and Cost of Redox-Active Organics for Aqueous Flow Batteries. ACS Energy Letters
2020, 879-884. DOI: 10.1021/acsenergylett.0c00140. Dieterich, V.; Milshtein, J.; Barton, J.; Carney, T.; Darling, R.; Brushett, F. Estimating the Cost of Organic Battery Active Materials: A Case Study on Anthraquinone Disulfonic Acid. Translational Materials Research
2018.

(2) Kwabi, D. G.; Ji, Y.; Aziz, M. J. Electrolyte Lifetime in Aqueous Organic Redox Flow Batteries: A Critical Review. Chemical Reviews
2020.

(3) Modak, S.; Kwabi, D. G. A Zero-Dimensional Model for Electrochemical Behavior and Capacity Retention in Organic Flow Cells. Journal of The Electrochemical Society
2021, 168 (8), 080528. DOI: 10.1149/1945-7111/ac1c1f.
(Invited) Hydrogen Oxidation Reaction (HOR) on Carbon-Capped Pd/C in Alkaline Media
Authors: Doan Huong , Sgarbi De Moraes Ricardo , Chatenet Marian
Published: July 2022

It is no secret alkaline fuel cells (AFC) using a liquid electrolyte (usually concentrated KOH) have assets over their proton-exchange membrane counterparts, in particular in niche applications where the latter are challenged by too harsh operating/environmental conditions [1]. AFC can also, in theory, use non-Pt catalysts at their electrodes without detrimental durability issues. However, recent studies from our group showed that Pt/C and Pd/C were very sensitive to the metal nanoparticles detachment from the carbon owing to their propensity to catalyze the carbon-support corrosion upon repeated alternation of the potential below/above their metal oxide potential (which is unavoidable at the anode upon start/stop of the fuel cell) [2-5].

In this presentation, it is highlighted that more robust hydrogen oxidation catalysts can be prepared by tailoring a carbon cap around the metal nanoparticles, in particular for palladium as the catalyst metal. Such “carbon-capped” Pd/C nanoparticles (ex. PdG2/C) exhibit a good compromise between their HOR activity and long-term stability (Figure 1), evaluated by identical location transmission electron microscopy upon accelerated stress tests (0.1 - 1.23 V vs. RHE stepped by 3 s – 3 s, 1000 times) (Figure 2). Their properties are very advantageous over non-capped (classical) Pd/C nanoparticles, demonstrating the interest of this strategy for the development of active and durable HOR catalysts for AFC anodes.

References

[1] G.F. McLean, T. Niet, S. Prince-Richard, N. Djilali, Int. J. Hydrogen Energy 27 (2002) 507-526.

[2] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, ACS Catal. 5 (2015) 4819-4824.

[3] A. Zadick, L. Dubau, U.B. Demirci, M. Chatenet, J. Electrochem. Soc. 163 (2016) F781-F787.

[4] C. Lafforgue, A. Zadick, L. Dubau, F. Maillard, M. Chatenet, Fuel Cells 18 (2018) 229-238.

[5] C. Lafforgue, F. Maillard, V. Martin, L. Dubau, M. Chatenet, ACS Catal. 9 (2019) 5613−5622.

Figure 1
How Hydrogen Evolution and Oxidation Reactions Proceed at the Platinum-Electrolyte Interface in Aqueous Solution
Authors: Jia Qingying , Sun Qiang , Myrthil Nathalie , Lopez Steven , Oliveira Nicholas J , Yan Yushan , Li Jingkun , Tyukhtenko Sergiy , Guo Jason
Published: July 2022

The hydrogen evolution and oxidation reactions (HER/HOR) are the most fundamental reactions in electrochemistry. They are also the electrochemical reactions taking place in practical devices such as H2 fuel cells and electrolyzers for the conversion between hydrogen fuel and electricity. Despite their fundamental and practical importance, the HER/HOR kinetics has remained not explicitly clear even for the platinum (Pt) electrode that has been mostly studied. This is manifested by the lack of consensus on why the HER/HOR rate of Pt is about two orders of magnitude slower in alkaline (pH = 0) than in acid (pH = 13),1 a long-standing puzzle in electrochemistry. Clear understanding of electrochemical reaction kinetics requires clear understanding of the charge transfer and chemical transformation at the electrode-electrolyte/membrane interface (EEI), which is however hampered by the lack of means to explore the complex electrochemical processes at the EEI in situ/operando.

Herein, by employing a set of N-methylimidazoles as the HER/HOR promotors and interface probes, we gave a reasonable explanation on how the HER/HOR of Pt proceeds within the EEI in aqueous solution.2 A combination of in situ spectroscopic characterization on the EEI showed that the N-methylimidazoles promoted the HER/HOR of Pt in alkaline solution by reorientating interfacial water against the interfacial electric field. We accordingly proposed that the HER/HOR in acidic and alkaline solution proceeds via diffusion of proton and hydroxide, respectively, through the H-bond network of interfacial water by the Grotthuss mechanism (Figure 1). We further demonstrated that adding 1,2-dimethylimidazole into the alkaline solution fed into the cathode of an anion exchange membrane electrolyzer led to an 40% performance improvement. The diffusion roles of interfacial water unraveled here may apply to many other electrochemical processes in aqueous solution.

Acknowledgements

This work was supported by the Office of Naval Research (ONR) grant N000141712608. This research used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory Contract DE-SC0012704. Beamline operations were supported in part by the Synchrotron Catalysis Consortium Grant DE-SC0012335.

Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energy Environ. Sci.
7, 2255-2260 (2014).

Sun et al. Mechanistic insights into pH-dependent hydrogen electrocatalysis by flipping interfacial water. Under revision by Nat. Energy.

Figure 1
(Keynote) Identification of Active Species and Mechanisms in Non-Precious Metal Oxygen Reduction Catalysts By Reductive Treatments and Magnetic Measurements
Authors: Gewirth Andrew A. , Esposito Anne Marie , Hua Qi
Published: July 2022

This talk addresses the Oxygen Reduction Reaction (ORR) utilizing Fe- and Co-based non precious metal (NPM) catalysts. There has long been uncertainty as to the active site for ORR in these materials due to the heterogeneity of the as-prepared catalyst. We report on two innovations directed at understanding the active sites in these materials. In the first, we interrogate the ORR activity in acid of a Fe porphyrin on different supports. While the activity is high when the Fe porphyrin is adsorbed on XC72 (a graphitic carbon), this activity is much lower when the porphyrin is adsorbed on either MoS2 or g-C3N4. Numerous physical characterization techniques show the electronic structure around the Fe center is the same for all three supports. Only the Fe porphyrin supported on XC72 exhibits a pH dependence in its ORR activity. This observation, coupled with the increased hydrophilicity of XC72 relative to the other supports, suggests that the support-electrolyte interaction controls the ORR activity. Modification of MoS2 to increase its hydrophilicity results in a more active ORR catalyst. In the second area, we use magnetometry and other techniques to examine the effect of two different reductive gas treatments on pyrolyzed ORR catalysts. We find that reductive gas treatments yield more superparamagnetic/ferromagnetic Fe species, with specific preparations yielding materials that consist almost entirely of reduced Fe (particularly Fe4N). Interestingly, catalysts exhibiting large percentages of superparamagnetic/ferromagnetic materials exhibit high activities for ORR catalysis as high as those reported in the literature.
(Keynote) Oxygen Reduction and Evolution in Ca2+ Containing DMSO on Atomically Smooth and Rough Pt and Au – Towards a Generalized ORR Mechanism in M2+ Containing DMSO
Authors: Koellisch-Mirbach Andreas , Bawol Pawel Peter , Park Inhee , Baltruschat Helmut
Published: July 2022

We demonstrate via cyclic voltammetry, differential electrochemical mass spectrometry (DEMS) and rotating ring disk electrode (RRDE) investigations with variation of the electrode surface roughness and atomically surface structure, that the CaO/CaO2 adsorbate layer formation determines the ORR product distribution. We found that on Pt electrodes peroxide is formed on the clean electrode, whereas superoxide is formed at the adsorbate covered electrode. We furthermore identified four key parameters, which strongly affect the ORR product distribution.

The electrode oxide interaction: A strong interaction shifts the product distribution to larger superoxide contribution.

The alkaline earth metal oxide interaction: A strong interaction shifts the product distribution to larger peroxide contribution.

The electrode surface area: A large electrode surface area delays the completion of the adsorbate layer and increases the peroxide contribution.

Electrode surface defects: Defects allow for faster nucleation and thus foster the adsorbate formation, which finally leads to a larger superoxide contribution.

Finally, reviewing earlier results of our group we provide a more general mechanism for the oxygen reduction alkaline earth metal cation containing DMSO, for a variety of electrode materials.

[1] A. Koellisch-Mirbach, I. Park, M. Hegemann, E. Thome and H. Baltruschat, ChemSusChem, (2021).

[2] P.P. Bawol, A. Koellisch-Mirbach, C.J. Bondue, H. Baltruschat and P.H. Reinsberg, ChemSusChem, 14 (2021) 428.
(Invited) Alloy of Platinum with Rare Earth Metals for High Oxygen Reduction Reaction Activity and Durability
Authors: Campos-Roldán Carlos Augusto , Parnière Alice , Donzel Nicolas , Pailloux Frédéric , Blanchard Pierre-Yves , Jones Deborah J. , Rozière Jacques , Cavaliere Sara
Published: July 2022

In the search for highly active and durable electrocatalysts for the oxygen reduction reaction (ORR), alloys of Pt with rare-earth metals (REM) have been demonstrated as one of the most promising candidates. However, their synthesis by conventional chemical methods is challenging, since REM have very low reduction potentials and high oxygen affinity leading to the formation of oxides rather than alloys.

We prepared a series of carbon supported Pt-REM nanomaterials with a solid-state method[1], characterized by physico-chemical techniques and evaluated towards the ORR in acidic medium.

The influence of the type of rare earth metal, of the Pt:REM ratio[2], of the post-synthesis treatment[3], and of the nature of the carbon support on the structural, morphological and electrochemical properties of the prepared electrocatalysts was investigated.

In this presentation we will give an overview of the results obtained on these highly active and durable carbon-supported Pt-REM nanostructured electrocatalysts and of the challenges to be tackled for their application at the cathode of proton exchange membrane fuel cells.

[1] Y. Hu, J.O. Jensen, L.N. Cleemann, B.A. Brandes, Q. Li, Synthesis of Pt–Rare Earth Metal Nanoalloys, J. Am. Chem. Soc. 142 (2020) 953–961.

[2] C.A. Campos-Roldán, F. Pailloux, P.-Y. Blanchard, D.J. Jones, J. Rozière, S. Cavaliere, Rational Design of Carbon-Supported Platinum–Gadolinium Nanoalloys for Oxygen Reduction Reaction, ACS Catal. 11 (2021) 13519–13529.

[3] C.A. Campos Roldán, F. Pailloux, P.-Y. Blanchard, D.J. Jones, J. Rozière, S. Cavaliere, Enhancing the Activity and Stability of Carbon-Supported Platinum-Gadolinium Nanoalloys towards the Oxygen Reduction Reaction, Nanoscale Adv. (2021). doi:10.1039/D1NA00740H.