bluuebunny/crossref_metadata_2025 huggingface dataset:
(Keynote) Single Atom Co-Catalysts in Photocatalytic H2 Generation
Authors: Schmuki Patrik
Published: February 2024

Photocatalytic H2 generation has been a highly investigated topic ever since Fujishima und Honda (1972) reported on the use of TiO2 as a solar-illuminated semiconductor for the splitting of water into H2 and O2. Generally, in a fully photocatalytic setting (when photogenerated electron and hole are transferred from a solution-suspended TiO2 nanoparticle to an aqueous electrolyte), a reasonable electron transfer rate can only be established when a noble metal co-catalyst is attached to the TiO2. Mostly this is a Pt nanoparticle that is deposited onto the TiO2 by various reductive treatments. Over the years numerous efforts have been devoted to the shrinkage of the particle to enhance the usage of the noble metal. Evidently the most extreme case shrinkage is the use of an insulated single atom of Pt. The use of such isolated atoms as a co-catalyst in photocatalysis has in recent years attracted strong interest, not only because the single atom state represents a maximized surface to volume efficiency, but also because single atom reactivity allows for unprecedented reaction pathways. In the presentation we discuss the use of Pt dispersed and anchored as single atoms on TiO2 nanocrystallites, powders and nanotubes as a co-catalyst in photocatalytic H2 generation. We discuss various trapping and stabilization approaches of SAs on photocatalysts and report on a SA-Pt photocatalyst with a higher photocatalytic activity than observed for classic arrangements of co-catalyst on the semiconductive substrate. Moreover, we show that a small fraction of the totally deposited Pt that is stably trapped SAs provides virtually all photocatalytic reactivity of a Pt decorated catalyst.

References

1) C. Gao, J. Low, R. Long, T. Kong, J. Zhu and Y. Xiong, Chem. Rev., 2020, 120, 12175-12216.

2) N. Denisov, S. Qin, J. Will,, T. Yokosawa, .. and P. Schmuki, Adv. Mater., 2022, n/a, 2206569.

3) S. Hejazi, ..O. Tomanec, S. Kment, and P. Schmuki, Adv.
Mater., 2020, 32, 1908505.

4) S. Qin, N. Denisov, J. Will, ..E. Spiecker and P. Schmuki, Solar RRL, 2022, 6, 2101026.

5) S. Qin, J. Will, H. Kim, N. Denisov, S. Carl, E. Spiecker and P. Schmuki, ACS Energy Lett., 2023, DOI: 10.1021/acsenergylett.2c02801, 1209-1214.

6) I. Hwang, A. Mazare, ..and P. Schmuki, Adv. Funct. Mater., 2022, n/a, 2207849.
(Invited) DFT Studies on Interactions between Heteropolyacids, Noble Metal Ions, and TiO2 Support
Authors: Tokarz-Sobieraj Renata , Niemiec Piotr , Rutkowska-Zbik Dorota
Published: February 2024

Heteropolycompounds of Keggin structure have been used as homogeneous and heterogeneous catalysts for decades. Recently, they gained popularity in photo- and electrocatalysis where they can be used as components of complex materials e.g., composed of metal ions/heteropolyacids/oxide-based supports.

The aim of the current theoretical studies is to characterize systems comprising of free and TiO2-supported heteropolyanions (PW12O40
3-, PMo12O40
3-) with embedded noble metal ions (Ag, Au, Cu, Pd, and Pt) acting as single atom catalysts. Their ground-state geometric and electronic structures were elucidated. Next, their redox and photochemical properties were determined: frontier (HOMO, LUMO) orbitals were defined, energy gaps and UV-VIS spectra were calculated, total and partial density of states were plotted and analysed. The interactions between components of the systems, in particular the influence of the support on the heteropolycompound electronic structure, were investigated. Next, the reactivity of the noble metal cations towards typical reagents (CO, H2, CH3, and C6H6) was studied.

The performed calculations demonstrated that the type of the metal and its oxidation state determines the energetics and character of the frontier orbitals, bond lengths and bond orders in their first coordination sphere, incl. the strength of their interactions with common reagents. The presence of TiO2 as the support is manifested by the emergence of new metal ion sitting sites, usually located at the interface between the heteropolyacid and the support, and modification of the redox properties of the systems.

Acknowledgements: This work was supported by the National Science Centre, Poland within Solar-Driven Chemistry project no 2019/01/Y/ST4/00024.
(Invited) Metal Oxide Mixed Sulphide of Controlled Crystal Structure As Catalysts for Two-Electron Water Oxidation
Authors: Slesinski Adam , Frackowiak Elzbieta
Published: February 2024

Conventional catalysts based on noble metals (Pt, Ru) are often used for production of oxygen during water electrolysis in four-electron pathway as they can decrease gas evolution overpotential. Another possible valuable product from water oxidation is hydrogen peroxide obtained via two-electron process. Currently, transition metal oxides, are readily employed to catalyse this reaction. Although they display certain activity, it is still not satisfactory for mass production of H2O2, therefore further optimisations are needed. We suggest in this work, in addition to typical nanostructure modifications of metal oxides (MoO2) such as doping or structural engineering, an application of transition metal dichalcogenides (MoS2). Consequently, the oxide is partially replaced by sulphur. The selection of molybdenum as a centre atom ensures sufficient electrical conductivity of material as an electrode active layer. This combination is intended to provide the benefits thanks to layered materials of tuned interlayer spacing as well as controlled number of active sites. It enables selective adsorption of intermediate products of water oxidation (O∗, OH∗, and OOH∗), and therefore increased preference towards two-electron pathway.

Various chemical approaches are considered to synthesize this material, especially hydrothermal treatment in autoclave and high-temperature sintering of precursors. The catalytic activity of the nanostructured metal oxide is further enhanced by its deposition on conductive high surface area support made of carbon/graphite particles of strictly defined textural parameters and surface chemistry. The final composite is obtained using hydrophobic binders (PVDF and PTFE) to form the electrode and improve the catalyst stability. The measurements are carried out in flow electrolyser unit with an alkaline electrolyte. The amount of produced H2O2, H2 as well as quantity and quality of evolved gases are assessed in terms of faradaic efficiency, pressure and overvoltage measurements.
Benchmarking Activity and Stability of Layered Double Hydroxides (LDHs) Electrocatalysts for Alkaline Water Electrolysis
Authors: Lloret Segura Vicent , Hartert Adrian , Seijas Da Silva Alvaro , Geuß Moritz , Freiberg Anna T.S. , Mayrhofer Karl J. J. , Thiele Simon , Abellán Gonzalo , Cherevko Serhiy
Published: February 2024

In order to reduce the cost of producing hydrogen through water electrolysis, novel technologies must be improved. Recently, the merging of conventional alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEM) has led to the development of anion exchange membrane electrolysis (AEMWE), which offers several advantages over AEL and PEM. In a nutshell, this technique employs cheap, abundant, and easily available (non-geostrategic) transition metals with anionic exchange membranes, overcoming the drawbacks of AEL and PEM.[1]

To reach the readiness level of this technology, new and scalable synthetic routes for catalysts that lower the overpotential of the sluggish oxygen evolution reaction (OER) are required. Amongst all the OER catalysts reported in the literature, Layered Double Hydroxides (LDHs) have gained increasing attention due to their low overpotentials and stabilities.[2] Besides, electrochemical protocols to determine the activity and stability of these catalysts in different electrochemical cells must be established to understand their properties. Thus, this work focuses on the advantages and limitations of different electrochemical techniques, such as rotating disk electrode (RDE), three-electrode cells, and single-cell tests, to determine the activity and stability of two different LDHs. Unlike laboratory scale LDHs ‒prepared by hydrothermal treatment (HT-LDH)‒ room temperature synthesized LDHs (RT-LDH) can be prepared in kilogram quantities and present chemical structure and morphology differences. In this work, the LDHs have been characterized with spectroscopic techniques to correlate the chemical structure and morphology of the materials to their electrochemical response by RDE, three-electrode cells, and single-cell measurements.

All in all, the scalable RT-LDH presents higher activity compared to HT-LDH in all three techniques. On the one hand, small current densities can only be reached by RDE, and the short-term stability of the materials is affected by the catalyst layer interface. On the other side, single-cell test measurements require long operational times, and the contribution of the membrane degradation to the overall cell voltage is still unclear. Thus, three-electrode cell measurements offer the possibility of characterizing LDHs at relevant current densities in a fast and straightforward manner, without membrane contributions, and are further employed in this work to study the stability of these systems.

References:

[1] N. Du, C. Roy, R. Peach, M. Turnbull, S. Thiele and C. Bock, Chemical Reviews, 122, 11830 (2022).

[2] R. Sanchis-Gual, A. Seijas-Da Silva, M. Coronado-Puchau, T. F. Otero, G. Abellán, E. Coronado, Electrochimica Acta, 338, 138613 (2021).
Enhanced Oxygen Evolution Reaction Activity and Structural Stability of Sulfur and Manganese Substituted Co(OH)2
Authors: Shamraiz Umair , Etzold Bastian J. M.
Published: February 2024

The search for efficient, cost-effective, and sustainable energy sources is a crucial challenge for the modern world.1, 2 In this regard, the development of effective electrocatalysts for water splitting, specifically the oxygen evolution reaction (OER), is a critical aspect of renewable energy technology.3, 4 In recent years, layered double hydroxides (LDHs) have emerged as promising materials for electrocatalysis due to their unique structural and electronic properties.5, 6

This study presents the synthesis and characterization of sulfur and manganese substituted Co(OH)2 as electrocatalysts for the oxygen evolution reaction (OER). The research employed a range of structural and physical characterization techniques, including XRD, EDX, SEM, TEM, and XPS to investigate the synthesized materials.

The OER activity was measured via LSV curves in 1 M KOH solution which showed that the S-Mn-Co(OH)2 has significantly low over-potential of 250 and 275 mV for current densities of 10 and 50 mA cm-2 when compared with the Co(OH)2. Additionally, the S–Mn–Co(OH)2 catalyst demonstrated after a 15 hours treatment at 50 mA cm−2 and in 1 M KOH only an overpotential increase of 34 mV and thus excellent stability. High-resolution transmission electron microscopy (HRTEM) analysis confirmed sheet like structure, while the XPS analysis revealed an increase in electron density around the Co owing to the presence of Co2+ and Co3+ in the sample. PXRD and HRTEM analysis also showed a slight reduction in the interlayer gap, indicating further stabilization of the layered structure. Both, stabilized the layered structure and increased electron density around Co could be reason for the enhanced OER performance and be important insights into the role of cation and anion substitution for enhancing LDH OER catalysts.

References

S. Chu and A. Majumdar, nature, 2012, 488, 294-303.

M. M. Rahman, I. Khan, D. L. Field, K. Techato and K. Alameh, Renewable Energy, 2022, 188, 731-749.

Y. Feng, H. Yang, X. Wang, C. Hu, H. Jing and J. Cheng, International Journal of Hydrogen Energy, 2022.

X. Liu, Y. Han, Y. Guo, X. Zhao, D. Pan, K. Li and Z. Wen, Advanced Energy and Sustainability Research, 2022, 3, 2200005.

P. Shandilya, R. Sharma, R. K. Arya, A. Kumar, D.-V. N. Vo and G. Sharma, International Journal of Hydrogen Energy, 2022, 47, 37438-37475.

A. Hameed, M. Batool, Z. Liu, M. A. Nadeem and R. Jin, ACS Energy Letters, 2022, 7, 3311-3328.
Assessing the Stability of Co3O4 Under Oxygen Evolution Reaction Conditions at Low and Mild pH
Authors: Priamushko Tatiana , Franz Evanie , Escalera López Daniel , Brummel Olaf , Libuda Jörg , Kleitz Freddy , Cherevko Serhiy
Published: February 2024

Water and CO2 electrolysis will play a crucial role in converting renewable energy into value-added chemicals and chemical fuels. To successfully employ and expand these technologies globally, ideally, one should develop Earth-abundant, cost-effective catalysts with high activity and stability. The requirements for the catalysts depend on the configuration of the electrolyzer, and the electrolyte used there. However, especially in CO2 electrolysis, the stability of the catalyst in a certain electrolyte does not guarantee its successful use on a long-term scale, as the pH in the electrolyzer may change during long-term experiments due to ion transfer through the membrane.1 The anode materials should, therefore, be stable across a broad pH range and/or in carbonate-rich electrolytes. Although the earth-abundant, non-noble transition metals, and their compounds are highly stable at higher pH, they are less stable than Ir or Pt at low and (near-)neutral pH.2 Interestingly, recent studies have shown that Co-based oxides exhibit promising stability even at low pH.3, 4 However, the nature of this stability as well as the mechanisms of non-noble metal oxides catalyzing OER at low or near-neutral pH, are yet to be discovered. In this work, we analyze the stability of cobalt oxide under various electrochemical conditions at low pH with the use of a scanning flow cell (SFC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) and differential electrochemical mass spectrometry (DEMS). By using these techniques, we can follow the dissolution of Co online and find potential narrow stability windows before and during the oxygen evolution reaction (OER). Benefiting from the obtained results, mitigating strategies for minimizing Co dissolution are proposed and discussed.

References:

(1) Vass, A.; Kormanyos, A.; Koszo, Z.; Endrodi, B.; Janaky, C. Anode Catalysts in CO2 Electrolysis: Challenges and Untapped Opportunities. ACS Catalysis
2022, 12 (2), 1037-1051. DOI: 10.1021/acscatal.1c04978.

(2) Vass, A.; Endrodi, B.; Samu, G. F.; Balog, A.; Kormanyos, A.; Cherevko, S.; Janaky, C. Local Chemical Environment Governs Anode Processes in CO2 Electrolyzers. ACS Energy Letters
2021, 6 (11), 3801-3808. DOI: 10.1021/acsenergylett.1c01937.

(3) Cherevko, S. Stabilization of non-noble metal electrocatalysts for acidic oxygen evolution reaction. Current Opinion in Electrochemistry
2023, 38. DOI: ARTN 10121310.1016/j.coelec.2023.101213.

(4) Li, A. L.; Kong, S.; Guo, C. X.; Ooka, H.; Adachi, K.; Hashizume, D.; Jiang, Q. K.; Han, H. X.; Xiao, J. P.; Nakamura, R. Enhancing the stability of cobalt spinel oxide towards sustainable oxygen evolution in acid. Nature Catalysis
2022, 5 (2), 109-118. DOI: 10.1038/s41929-021-00732-9.
Theoretical Study on Inhibition of Oxygen Evolution in Layered Cathode Materials during Charging
Authors: Lin Kuan-Yu , Xu Shi-Hong , Nachimuthu Santhanamoorthi , Jiang Jyh-Chiang
Published: February 2024

In recent years, Ni, Mn-based layered cathode materials (Li1.2Ni0.2Mn0.6O2, LiNi1-x-yCoxMnyO2) have shown great promise for high energy density LIBs. Research has shown that nickel-rich materials are ideal candidates for high-capacity batteries. The valence state from Ni2+ to Ni4+ allows more Li+ to transfer between the cathode and anode, providing excellent electrochemical performance. However, the oxidation of oxygen atoms triggers irreversible structural rearrangements on the surface, while Ni3+ introduces Jahn-Teller distortion. At high voltages, the stability of layered cathode materials is severely hampered. We present theoretical work on Li1.2Ni0.2Mn0.6O2 and LiNi1-x-yCoxMnyO2 using density functional theory, considering cation- and anion-doped surface treatments. We found that doped layered cathode materials successfully suppressed O2 formation at highly delithiated levels. Through DFT calculations, we understand the mechanism of oxygen evolution from layered cathode materials during the charging process and discover how to suppress oxygen evolution strategies.
(Invited) Optimization of Carbonate Electrolytes for Lithium Metal Anodes
Authors: Lucht Brett L.
Published: February 2024

A solid electrolyte interphase (SEI) is generated on the anode of lithium ion batteries during the first few charging cycles. While the SEI generated for LiPF6/carbonate based electrolytes is stable on graphite anodes, the stability of the SEI is poor for LiPF6/carbonate based electrolytes with lithium metal anodes. However, modification of the carbonate based electrolytes via incorporation of alternative salts and/or electrolyte additives significantly improves the stability of the SEI and the cycle life of lithium metal anodes. Investigations of the SEI structure have been conducted via a combination of XPS, IR-ATR, SEM, and TEM. Mechanisms for the generation of the complicated mixture of products are presented along with the differences in the SEI structure and function.
Fabrication and Model-Guided Design of Thick-Format Lithium Ion Electrodes
Authors: Hu Kedi , West Alan C. , Steingart Daniel A.
Published: February 2024

To enable the use of renewable energy in place of fossil fuels for grid-scale electricity generation, low-cost, long-duration (3 hr charge, 12 hr discharge) energy storage systems must be developed to bridge the intermittency of these resources. This present work explores the adoption of thick-format lithium-ion electrodes to minimize inactive material cost and achieve <$100/kWh of storage. Thick lithium iron phosphate (LFP) pellets were fabricated using a dry pressing process, and the effects of composition, thickness/porosity balance, and electrolyte choice on the performance of the LFP half cells were explored. LFP electrodes with thicknesses up to 1 mm and capacities up to ~15 mAh/cm2 exhibited good rate performance (~90% utilization at a C/10 rate) and stable cycling over 100 cycles. A physics-based model was used to study transport within these thick electrodes. As thickness increases, large concentration gradients form across the electrode, with salt depletion at the current collector and salt accumulation at the separator exceeding the solubility limit of conventional electrolytes. Unlike fast-charging thin electrodes where kinetic overpotentials dominate inefficiencies, thick electrode performance is diffusion-limited, suggesting that methods for minimizing tortuosity and increasing ionic conductivity will be key in enabling low-cost thick electrodes.

Figure 1
Electrode Parameterization as an Investigative Tool for Solid Electrolyte Interphase Evolution Monitoring on Commercial Lithium-Ion Battery Electrodes
Authors: Jackowska Roksana , Chen Yongxiu , Spathara Dimitra , Kendrick Emma
Published: February 2024

The formation process is one of the most critical aspects of lithium-ion battery (LIB) production. It involves the creation of an interface layer known as solid electrolyte interphase (SEI). The layer predominantly forms during the first few charging cycles of the battery, resulting in approximately 10% capacity reduction [1]. However, forming a stable SEI layer is critical in ensuring uniform cell capacity, safe operation, and a long lifetime of LIBs [2].

The thickening of the SEI layer is one of the main contributors to capacity fade over the battery lifetime and strongly depends on electrochemical cycling conditions [1]. Despite its importance, there are still no comprehensive theories and models describing SEI formation and evolution. The difficulties arising from its characterization could explain why various structure models have appeared in the literature [3–5]. Therefore, it is indispensable to go beyond traditional characterization methods to fully elucidate the SEI layer behaviours.

In this work, we investigate changes in the kinetic and thermodynamic electrode parameters with growing SEI layer thickness, deriving relevant variables, such as exchange current density, electrode tortuosity, and lithium diffusion coefficient from experimental data. The measurements are performed on commercially relevant electrodes. Parameter evolution monitoring will contribute to developing a predictive understanding of the SEI layer evolution under different cycling conditions, and to unlocking improvements in LIB sustainability by prolonging their lifetime and enhancing safety.

References:

[1]. Edge, J. S. et al. Lithium ion battery degradation: what you need to know. Physical Chemistry Chemical Physics vol. 23 8200–8221 (2021).

[2]. Wood, D. L., Li, J. & Jin An, S. Formation Challenges of Lithium-Ion Battery Manufacturing. Joule 3, 2884–2888 (2019).

[3]. Peled, E. The Electrochemical Behavior of Alkali and Alkaline Earth Metals in Nonaqueous Battery Systems — The Solid Electrolyte Interphase Model. J. Electrochem. Soc. 126, 2047–2051 (1979).

[4]. Aurbach, D. Review of selected electrode – solution interactions which determine the performance of Li and Li ion batteries. J. Power Sources 89, 206–218 (2000).

[5]. Peled, E., Golodnitsky, D. & Ardel, G. Advanced Model for Solid Electrolyte Interphase Electrodes in Liquid and Polymer Electrolytes. J. Electrochem. Soc. 144, L208–L210 (1997).
Position-Dependent Storage in Mixed Conductors: Generalized Storage Model, Improved Mott-Schottky Analysis and Correct CV-Response
Authors: Xiao Chuanlian , Wang Hongguang , Usiskin Robert , van Aken Peter A , Maier Joachim
Published: February 2024

In this work, TiO2 and Nb2O5 thin films have been used as model systems to study the fundamental issues related to charge storage and transport in solids. Firstly, the storage capacity of lithium in TiO2 as a function of thickness for various electron-accepting substrates is measured precisely. Contributions from bulk and boundary storage were deconvoluted based on the electrochemistry and electron microscopy results. The results allow for working at three basic points. (1) Such experimental and theoretical investigation of the bulk and interfacial defect chemistry enables deriving the entire profile and embedding bulk and boundary contributions into a common generalized thermodynamic model, and hence a unification of battery intercalation electrode and supercapacitive storage1. (2) Bias-dependent resistance and capacitance measurements across the LixTiO2/electronic conductor interface allow us to improve the Mott-Schottky model by implementing a charge density that has been determined by the preparation conditions2. (3) Cyclic voltammetry (CV) performed at these systems leads to a description that is adjusted to the solid state and deviates significantly from the description in liquids. All these fundamental studies are highly relevant to energy-related application3.

1. C. Xiao, H. Wang, R. Usiskin, P. A. van Aken, J. Maier, submitted.

2. C. Xiao, J. Maier, in preparation.

3. C. Xiao, R. Usiskin, J. Maier, in preparation.
(Invited) Revealing Charge Storage Processes at the Interfaces of Supercapacitor Electrodes
Authors: Wang Xuehang
Published: February 2024

The fast development of electrochemical energy storage devices has revolutionized almost every aspect of modern life by enabling portable electronic devices, electric vehicles, and grid storage of renewable energy. To satisfy the growing industrial and consumer needs for energy storage systems with high output power and short recharge time, the electrode materials should have excellent high-rate performance.1

Electrical double-layer (EDL) capacitors exhibit high-rate capability and long-cycling life as they store charges electrostatically. Using ionic liquid (IL) as the electrolyte leads to a large voltage window but low capacitance. In this first session of the presentation, I will introduce a mathematical model to simulate the IL ion packing structure in nanopores. This model is capable of estimating the EDLC capacitance based on pore size distribution. Then, we further revealed that mixture IL ions can be selectively driven into the pores of different confinement levels, which was confirmed by solid-state NMR, and further explained by DFT simulation2.

In the second part of the presentation, I will shift to pseudocapacitors, which are expected to have a much higher charge storage capacity than EDL capacitors and a much higher rate than batteries as they store energy through fast surface redox reactions.3 The emerging 2D material family, 2D transition metal carbides/nitrides MXenes, shows outstanding pseudocapacitive performance due to their ionophilicity, metallic conductivity, and highly reactive surfaces. The proper coupling between electrolyte and electrode is critical to increase energy and power density. In the organic electrolyte, we found that the solvent has a strong impact on the ion/solvent arrangement in 2D MXene material and hence the charge storage capability.4 In the aqueous electrolytes, we successfully introduced surface redox reactions to MXene electrodes by using the water-in-salt electrolytes and by adjusting the initial valence of Ti in Ti3C2 MXenes, which dramatically increases the capacitance of MXene in the neutral aqueous electrolytes5.

References

Simon, P.; Gogotsi, Y., Nat. Mater.
2020,
19 (11), 1151-1163.

Wang, X.; Mehandzhiyski, A. Y.; et al., J. Am. Chem. Soc.
2017,
139 (51), 18681-18687.

Fleischmann, S.; Mitchell, J. B.; et al., Chem. Rev.
2020,
120 (14), 6738-6782.

Wang, X.; Mathis, T. S.; et al., Nat. Energy
2019,
4 (3), 241-248.

Wang, X.; Mathis, T. S.; et al., ACS Nano
2021,
15 (9), 15274-15284.
Exploring Operando Electrochemical Techniques to Track Degradation Mechanisms in Li-Ion Batteries
Authors: Leal de Souza Matheus , Morcrette Mathieu , Simon Patrice
Published: February 2024

The battery field has recently received unprecedented attention and investments in order to handle the upcoming demands of energy storage notably from the electric mobility sector. The pursuit of higher performance batteries that store more energy, charge faster and have a longer life cycle has been converted into studies for new electrode materials, coatings, electrolytes, among others that often find the common key challenge of the performance decline. The precise identification of the degradation mechanisms and their tracking along aging is thus essential to pave the way for the next generation batteries. For that several methods are employed although most of them are not in operando, not following the practical cell operation. In that context, this paper introduces a set of operando electrochemical techniques that are still largely underexploited but that can be coupled and offer broader comprehension of the degradation mechanisms through deeper than usual analysis of electrochemical data. Taking insertion cells (like Li ion or Na ion batteries) as example it is first shown how differential techniques like incremental capacity analysis (ICA or dQ/dV vs V) and differential voltage analysis (DVA or dV/dQ vs Q) allow to identify main degradation mechanisms in the positive and in the negative electrodes separately by following their active material masses and their curves dynamics (relative displacement of the potential x capacity curves, the slippage) in a two electrodes configuration. For that the in house and free access developed software Electrochemical Visualization Application (EVA) is employed. In addition, using defined protocols, other techniques as Distribution of Relaxation Times (DRT) are coupled to those first analyses in order to complement the understanding of the degradation mechanisms in each electrode. This presentation intends to show an introduction of how to deeper analyze electrochemical techniques to follow loss of mass and lithium ion inventory from each electrode along aging, how to use the DRT with the ICA and DVA to identify the evolution of Impedance from each electrode along aging and how to build protocols that allow to couple those techniques minimizing any eventual degradation interference from those techniques, that all shown through experimental results and with the aid of a free and open software for the part of the ICA and DVA analyses.

Figure 1
(Invited) Modeling of the Electric Double Layer (EDL) at Li/SEI/Electrolyte Interfaces
Authors: Qi Yue
Published: February 2024

Liquid electrolytes, consisting of salts, solvents, and additives, must form a stable solid electrolyte interphase (SEI) to ensure the performance and durability of lithium(Li)-ion batteries. However, the electric double layer (EDL) structure near charged surfaces is still unsolved, despite its importance in dictating the species being reduced for SEI formation near a negative electrode. Recently, we have developed an interactive Molecular Dynamics -Density Functional Theory -data statistics (MD-DFT-data) model to investigate the reduction reactions of multicomponent electrolytes within the EDL. We will illustrate the effect of EDL on SEI formation in two essential electrolytes, the carbonate-based electrolyte for Li-ion batteries and the ether-based electrolyte for batteries with Li-metal anodes. Our results reveal that the role of fluoroethylene carbonate (FEC) additive differs drastically in the two electrolytes as an SEI modifier to form the beneficial F-containing SEI component (e.g., LiF). The competition among the cations, anions, and various species in the solvents with a charged surface at different temperatures can all jointly determine the EDL structure and therefore the SEI compositions. [1]

While the classical Poisson–Boltzmann EDL model developed for fully solvated ions face new challenges in high-concentration liquid electrolytes (HCE), localized high-concentration liquid electrolytes (LHCE) as well as solid electrolytes (SE), new theoretical developments are required. We will introduce a new DEL model in SE and SEI by solving the DFT-informed Poisson–Fermi–Dirac equation and demonstrate how it can be used for interlayer thickness design. [2]

[1] Wu, Q.S, McDowell, M.T., & Qi, Y., Journal of the American Chemical Society 145 (4), 2473-2484 (2023)

[2] Swift, M.W., Swift, J.W. & Qi, Y. Modeling the electrical double layer at solid-state electrochemical interfaces. Nat Comput Sci
1, 212–220 (2021)
Interface Induced Fast Ion Conduction in Complex Hydride/Oxide Nanocomposites: Interplay between Hydride and Oxide Properties
Authors: Ngene Peter
Published: February 2024

Solid-state electrolytes are crucial for next generation batteries with high energy density, long lasting and improved safety. The compatibility of most solid electrolytes with metallic anodes such as Li and Na metals, and cathodes such as sulfur, makes them suitable for high-capacity batteries (e.g., Li-S). They also address the safety concerns of current batteries by eliminating the flammable organic solvents in liquid electrolytes and by preventing/limiting dendrite formation.

The lithium and sodium containing complex metal hydrides (e.g., LiBH4, NaBH4, LiCB11H12) have recently gained attention as solid-state electrolyte. They show high ionic conductivities but only at elevated temperatures (typically above 110 °C). Extending the high ionic conductivities to ambient temperatures is pivotal to the application of this fascinating class of solid electrolytes [1].

In this contribution, we will use LiBH4 and NaBH4 as examples to show that the ionic conductivities of complex hydrides can be greatly enhanced through interface effects resulting from the formation of nanocomposites with metal oxides. This strategy can lead to several orders of magnitude increase in the room temperature ionic conductivity [2]. Using DSC, DRIFT, solid-state NMR, and XRS (Xray Raman scattering), I will discuss how nanocomposite formation and presence of interfaces modifies either the phase stability, the defect concentration and/or leads to the formation of tertiary phase, and thereby increase profoundly the ion mobility of the complex hydrides. Systematic studies with different oxide nanoscaffolds and surface modified metal oxides, reveal that these effects can be optimized by tuning/engineering the nanostructure and interfaces in the nanocomposites. [3-4]. We will show that the effects also depend on a complex interplay between the stability of the metal hydride and surface properties of the metal oxide. Finally, the performance of some of the nanocomposite electrolytes in all-solid-state batteries, will be highlighted [5]

References

[1] L.M de Kort, P. Ngene et al. J. Journal of Alloys and Compounds 901 (2022) 163474

[2] D. Blanchard et al., Advanced Functional Material. 25 (2015), 182.

[3] P. Ngene et al. Physical Chemistry Chemical Physics 21 (40), 22456-22466

[4] L.M de Kort, P. Ngene et al. Journal of Materials Chemistry A 8.39 (2020): 20687-20697

[5] D. Blanchard et al, J. Electrochem. Soc. (2016).
X-Ray Absorption Spectroscopy Studies of Ti-Mn Redox Flow Battery to Clarify the Redox Reaction
Authors: Asakura Daisuke , Hosono Eiji , Kitamura Miho , Horiba Koji , Magome Eisuke , Setoyama Hiroyuki , Kobayashi Eiichi , Yuzawa Hayato , Ohigashi Takuji , Sakai Takaaki , Kanega Ryoichi , Funaki Takashi , Sato Yukari , Ohira Akihiro
Published: February 2024

Redox flow battery (RFB) is a promising candidate of large-scale stationary energy storage which is necessary to utilize renewable energy. For RFBs, the capability to easily increase the capacity by enlarging the electrolyte tank, high charge-discharge cycle performance, and wide flexibility to high- and low-frequency fluctuations are highly advantageous.

Nowadays vanadium RFBs are used for practical use, but the material cost of vanadium is problematic to further spread them. An alternative candidate for commercial use is titanium-manganese (Ti-Mn) RFBs [1] whose material cost should be lower. On the other hand, the stability of the electrolyte for positive electrode (catholyte) need to be improved, because precipitates are created by a charge disproportionation reaction of Mn ions in the charged catholyte [2]. The formation of precipitates decreases the energy density and degrades the cyclability. To improve the characteristics, the chemical state and redox reaction of the electrolytes of Ti-Mn RFBs should be clarified by precise analyses.

We performed synchrotron radiation X-ray absorption spectroscopy (XAS) for the electrolytes of a Ti-Mn RFB to directly observe the redox reaction [3]. In this study, the same Ti-Mn RFB electrolyte was used for both positive and negative electrodes. The Ti K-edge XAS of the electrolyte for negative electrode (anolyte) revealed gradual reduction reaction of Ti from Ti4+ on the charge process. The Ti L
2,3-edge XAS spectrum for the anolyte at state of charge (SOC) of 80% was mostly attributed to Ti3+ state. The results for Ti are consistent with electrochemical views in previous reports [2]. The Mn K-edge XAS of the catholyte gradually shifted to higher energy-side up to SOC of 50%, indicating a slight oxidation reaction of Mn from Mn2+. However, the Mn L
2,3-edge XAS spectrum for the catholyte solution at SOC of 80% was of Mn2+ state that was not changed from the initial state. Instead, scanning transmission X-ray microscopy (STXM; XAS mapping with a high spatial resolution) at the Mn L
3-edge unveiled that the precipitates mostly consist of Mn4+. Thus, the charge disproportionation reaction of 2Mn3+ -> Mn2+ (solution) + Mn4+ (precipitates) in the charged catholyte was confirmed. In the presentation, the electronic-structure change of the Ti and Mn ions in both catholyte and anolyte will be discussed in detail.

References

[1] T. Shigematsu, Curr. Opin. Electrochem.
18 (2019) 55-60.

[2] Y. R. Dong et al., SEI Technical Review
84 (2017) 35-40.

[3] D. Asakura et al., Chem. Asian J.
18 (2023) e202201047.
High-Throughput Screening of Molecules for Flow Batteries
Authors: Peljo Pekka , Gonzalez Gabriel , Martínez González Eduardo , Li Qiujun , Hannonen Jenna , Mattinen Ulriika , Hamza Andrea , Németh Flora , Madarasz Adam , Papai Imre , Nechaev Anton , Pihko Petri M
Published: February 2024

Development of next generation stationary energy storage technologies is of crucial importance for increasing the share of the intermitted renewable electricity generation in the world. Traditional trial and error based approach for discovery of novel materials is very slow, so we have been thinking of how to accelerate the process. Some crucial parameters such as redox potentials can be readily evaluated with computational tools, such as those developed in our CompBat project [1], [2], but other parameters such as stability are more difficult to be evaluated. In this work we will demonstrate our web-based application for evaluating redox potentials of molecules from the SMILES structure, illustrating very impressive or problematic performance depending on the training data used for the model.

For the question of stability, we believe that sufficient quantity of experimental data is required for training of specific machine learning models for stability prediction. For this purpose, we will illustrate our experimental approach for high-throughput electrochemistry, to evaluate the stability of molecules in the time-scale of voltammetry. Moreover, we will discuss the order of magnitude of the kinetics of the decomposition reactions that can be evaluated by voltammetry, and illustrate that voltammetry is a good tool for roughly separating more stable species from the less stable, but other techniques are required for evaluating stability in the time scale of battery operation.

References

https://compbat.eu/

A. Hamza, F.B. Németh, Á. Madarász, A. Nechaev, P. Pihko, P. Peljo, I. Pápai, N-alkylated pyridoxal derivatives as negative electrolyte materials for aqueous organic flow batteries: Computational screening, 10.26434/chemrxiv-2023-bzc6w
Stability of Highly Soluble Ferrocyanides at Neutral pH for Energy Dense Flow Batteries
Authors: Reber David , Thurston Jonathan R. , Becker Maximilian , Marshak Michael P.
Published: February 2024

Ferro- and ferricyanides are among the most employed positive electrolyte materials in aqueous flow battery research but the limited solubility of commonly available sodium and potassium salts is a critical factor limiting application at scale. We systematically study the cation dependent solubility of these materials and, importantly, the cation dependent stability of the anion in aqueous solution. For Li4Fe(CN)6 we report a maximum solubility of 2.3 M and show stable cycling of a 2 M symmetric cell (54 Ah L−1) over 200 days, and also demonstrate solubilities of 1.6 M for ammonium and calcium salts. Importantly, we observe cation dependent electrolyte stability in long-term experiments and investigate the pronounced anion decomposition observed in presence of ammonium cations.[1]

While achieving high solubilities leads to increased energy densities, concentrated electrolytes present many challenges such as high osmotic strength and high viscosity. This is particularly pronounced in electrolytes that employ ions with high charge states such as ferrocyanide. Furthermore, the selected cation needs to be compatible with the membrane in the cell.[2] We thus outline several often neglected design aspects that must be considered when developing new active materials for aqueous flow batteries.

[1] Reber, D., Thurston, J.R., Becker, M., Marshak, M.P., Stability of highly soluble ferrocyanides at neutral pH for energy dense flow batteries, Cell. Rep. Phys. Sci. 2022, 4, 101215

[2] Waters, S.E., Thurston, J.R., Armstrong, R.W., Robb, B.H., Marshak, M.P., Reber, D., Holistic design principles for flow batteries: Cation dependent membrane resistance and active species solubility J. Power Sources 2022, 520, 230877
Electrochemical Evaluation of Manganese Electrolytes for Redox Flow Batteries
Authors: Villar Erlantz , Khataee Amirreza , Lindstrom Rakel
Published: February 2024

Redox flow batteries (RFBs) are promising candidates for long-duration energy storage mainly due to the lower cost of improving the energy density compared to lithium-ion batteries. However, the full sustainability of RFBs has not been achieved yet, and there is a lot of room for further improvement. One of the main parameters showing a strong influence on the sustainability of RFBs is redox active materials. In this work, manganese was selected for electrochemical evaluation as it fulfills the sustainability requirements. Manganese is a non-toxic, low-cost and abundant material with sufficient aqueous solubility[1]. Moreover, the standard potential of manganese (1.51 V) is higher than that of vanadium (1.26 V).

For electrochemical parameters, we have, through cyclic voltammetry (CVs) and polarization curves, estimated the diffusion coefficient (D0
) and heterogeneous standard electron transfer rate (k
0) of manganese in an acidic electrolyte in the presence of titanium as an additive. In order to investigate the performance of an RFB system using a manganese electrolyte, a hybrid system was designed that uses hydrogen gas on the negative side and an acidic manganese electrolyte the positive side. We have studied the resistance behavior of the hybrid RFB through electrochemical impedance spectroscopy at different states of charge. From EIS data, cell ohmic resistance, and a general idea of the different processes taking place at different state of charge were obtained. Moreover, we studied the performance of the hybrid RFB during 70 cycles, obtaining an average coulombic efficiency of 98.1%, voltage efficiency of 77.8% and capacity retention of 97.7%.

Carney, J.R., B.R. Dillon, and S.P. Thomas, Recent Advances of Manganese Catalysis for Organic Synthesis. European Journal of Organic Chemistry, 2016. 2016(23): p. 3912-3929.
Fabrication and Performance of Symmetric Flow Battery Systems Incorporating Novel Pyridinium Anolytes
Authors: Samaroo Sharmila , Hengesbach Charley , Opolka Taylor D. , Kruper William R. , Hickey David , Guarr Thomas F.
Published: February 2024

The push to bring more renewable energy sources onto the grid has spawned a flurry of work to develop viable options for long duration energy storage. Redox flow batteries (RFBs) represent one of the most attractive possibilities, and research toward employing redox-active organic materials to improve or replace the incumbent commercially available vanadium-based RFB technology is burgeoning. In particular, numerous pyridinium-based salts have been extensively studied as anolytes in both aqueous and nonaqueous RFBs. We have recently reported a series of readily synthetically accessible 2,6-dimethyl-4-arylpyridinium compounds that display quite negative reduction potentials (ca. -1.55 to -1.8 V vs Fc/Fc+), along with high solubility and excellent electrochemical kinetics. Some of these materials are also extremely persistent in the reduced state, suggesting that they may be good candidates for RFB applications.

In this presentation, we will describe the preparation and properties of new pyridinium compounds from the corresponding pyrylium precursors, as well as the fabrication of symmetric RFB systems in which these materials are covalently linked to phenothiazine or ferrocene catholyte moieties. Synthesis, solubility, and electrochemical performance (including preliminary RFB cycling data) of these materials will also be discussed.
Electrode Imbibition and Surfactant Interactions with Vanadium Flow Battery Electrolytes
Authors: Imel Adam , Barth Brian , Zawodzinski Thomas A.
Published: February 2024

Redox flow batteries (RFB) are a critical technology for stationary grid-scale energy storage, with potential usage with intermittent power sources, such as wind and solar. RFBs are attractive for long-duration energy storage because the anolyte and catholyte are stored separately external to the electrochemical reactor. Separating the electrolytes and the electrochemical cell decouples energy and power densities, unlike batteries that store charge in the solid-state, such as Li-ion, Pb-acid, or Ni-Cd. A standard RFB chemistry is the all-vanadium redox flow battery (VRFB), which utilizes the four oxidation states of vanadium, with V2+, V3+, V4+, and V5+. Recently our group found that adding small amounts of sodium dodecyl sulfate (SDS) to a VFRB increased the kinetics of the V2+ to V3+oxidation.

Furthermore, surfactants play essential roles in battery manufacturing and operation. Surfactants can change metal oxide crystal structure, inhibit dendrite growth, limit corrosion, and prevent nanoparticle agglomeration. Surfactants are never wholly removed during manufacturing and can be present during battery operation. Therefore, it is crucial to understand how surfactants impact battery performance and their effect on the materials.

This talk describes SDS's equilibrium surface properties and adsorption characteristics at the liquid−air and liquid-solid interfaces, thus providing insights into the interactions of SDS with a VFRB electrolyte. Experiments focusing on the effects of sulfuric acid and vanadium ions on SDS's equilibrium surface tension and critical micelle concentration (CMC) were completed. The Szyszkowski equation is used to calculate SDS's adsorption parameters, such as interfacial surface excess, Γsz [mol/m2], the surface excess at the saturated interface, Γ∞ [mol/m2], the minimum molecular area in the adsorption layer at the saturated interface, Amin [nm2], and the Gibbs free energy of adsorption, ΔGads [kJ/mol]. Furthermore, an examination of the spontaneous imbibition of the VFRB electrolyte with SDS into a porous carbon electrode is presented. The microstructure of porous systems, interfacial tension, and fluid−solid interactions controls the capillary-driven flow and is vital in multiphase flow in porous media. Therefore, understanding SDS's effects on the VFRB electrolyte in an electrode is critical to understanding the electrochemical reactions and molecular interactions occurring.

This work was supported as part of the Breakthrough Electrolytes for Energy Storage and Systems (BEES2), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0019409.