bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Formation of Liquid Tb–Zn Alloys in Molten LiF–CaF2–TbF3
Authors: Kawaguchi Kenji , Nohira Toshiyuki
Published: December 2024

Terbium (Tb) is added to neodymium magnets used in motors for electric vehicles (EVs) and hybrid electric vehicles (HEVs) to prevent deterioration of their magnetic properties at high temperatures. Tb metal added to neodymium magnets is currently produced by metallothermic reduction. As a novel method for producing Tb metal, we focused on the electrochemical reduction of Tb (III) ions using a liquid Zn electrode. In this study, the electrochemical formation of Tb–Zn Alloys was investigated at the liquid Zn electrode in molten LiF–CaF2–TbF3 at 1123 K.

Cyclic voltammetry and galvanostatic electrolysis were performed after adding TbF3 to molten LiF–CaF2 (80.5:19.5 mol%) in a graphite crucible under an Ar atmosphere at 1123 K. The working electrodes were a Mo flag (Φ 3 × 0.1 mm) and liquid Zn (7 g) held in a small boron nitride crucible. A graphite rod was placed in contact with the bottom of the graphite crucible, and the entire graphite rod and crucible were used as the counter electrode. A Ti rod was used as the quasi-reference electrode. The potential was calibrated using the Li+/Li potential. The samples obtained by galvanostatic electrolysis were analyzed by SEM/EDX.

Cyclic voltammetry was performed at Mo flag and liquid Zn electrodes. At the Mo flag electrode, in addition to the redox peaks of the deposition and dissolution of Li metal, the reduction current from c.a. 0.2 V (vs. Li+/Li) and a corresponding oxidation current were observed, which were attributed to the deposition and dissolution of Tb metal. At the liquid Zn electrode, an increase in the reduction current was observed from c.a. 1.0 V. This suggests the formation of the liquid Tb–Zn alloy. Galvanostatic electrolysis was performed using the liquid Zn electrode at –100 mA cm–
2 for 210 min. Figure 1 shows cross-sectional (a) optical image and (b) SEM image of the sample after electrolysis. The formation of the Tb–Zn alloy was confirmed by EDX analysis.

A part of this study was conducted as commission research with the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Figure 1
Theoretical Study of Ion Pairing in Protic Ionic Liquids of ΔpKa range 6 to 18
Authors: Rana Smit S. , Cayer Justin , East Allan L. L.
Published: December 2024

Studies on “poor” protic ionic liquids, having proton-transfer strength ΔpKa = 0-6, have shown the need to make corrections to the Fuoss equation for prediction of ΔGioniz and Kioniz for ion-pairing equilibria in these systems. Recent work built empirical functions to replace the Fuoss equation for this ΔpKa region, based on ab initio ion-pairing energies, but the functions did not perform well at the higher end of this range. Here, we extend the study to the range ΔpKa = 6-18, examining hypothetical mixtures of trimethylamine (TEA) with acids from weak (CH3COOH) to quite strong (CF3SO3H). Ab initio pairing energies were obtained for these systems, followed by refitting. It is hoped that the data will improve the understanding of the dependence of ionicity of these systems with increasing ΔpKa, with hopes of explaining (i) the known maximum of ionic conductivity vs ΔpKa, and (ii) the optimal acid/base mixing ratios (not always 1:1) for maximum conductivity.
Polymer Inclusion Membranes Based on Ionic Liquids for Cobalt, Nickel, and Lithium Ions Separation
Authors: Luo Huimin , Adigun Babafemi , Prasad Thapaliya Bishnu , Dai Sheng
Published: December 2024

The proper handling of end-of-life (EOL) lithium-ion batteries (LIBs) has become an urgent and challenging issue with the surging use of LIBs, in which recovering high-value cathode materials from EOL LIBs not only relieves the pressure on the raw material supply chain, but also minimizes environmental pollution of EOL LIBs. These spent LIBs pose significant environmental challenges due to the potential release of toxic but useful materials, including cobalt, nickel, and lithium. The efficient recovery of these valuable metals is crucial for both environmental sustainability and resource conservation. Existing separation technologies have disadvantages, including the use of large quantity solvents, prompting the need for the development of economical, efficient, and ecofriendly processes for recovering these valuable materials. A membrane system using ion-exchange polymer inclusion membranes (IEPIM) based on ionic liquids (ILs) has been developed for the separation of these metal ions. Our approach relies on proton pumping in ILs, which is driven by the pH gradient between the feed and stripping solutions and facilitates the metal ion transport through the membrane, making the separation process effective while avoiding the use of large quantity solvents. Through systematic experimentation and optimization, cobalt and nickel ions were selectively transported from lithium ions in an aqueous feed solution into a hydrochloric acid receiving solution, effectively separating these metal ions. The IEPIM demonstrated good selectivity and efficiency in metal ion separation, achieving high recovery rates (~90%) of these metals and maintaining the recovery rate over several cycles, indicating high stability over successive use, thus providing a promising and sustainable process for the separation of cathode materials from spent EOL LIBs. These results indicate that the IEPIM can be used as a viable alternative to the conventional method of metal ion separation. Recent results of different ILs concentration effects and other experimental conditions will be discussed in this presentation.
Evaluation of the Solid-Electrolyte Interphase Formation in a Bis(fluorosulfonyl)amide Based Ionic Liquid in the Presence Lithium Ion Using Different Redox Probes
Authors: Momose Shunosuke , Thomas Morgan L. , Serizawa Nobuyuki , Katayama Yasushi
Published: December 2024

The solid electrolyte interphase (SEI) is formed on the anode surface of rechargeable Li batteries by the reductive decomposition of the electrolyte. Because the SEI enables the anode reactions involving lithium ions and prevents further electrolyte decomposition, the SEI is one of the important factors affecting the battery performance.

Ionic liquids (ILs) have been investigated as the electrolytes for rechargeable Li batteries because of their favorable properties such as non-flammability and non-volatility. An amide-type IL composed of 1-butyl-1-methylpyrrolodonium (BMP+) and bis(fluorosulfonyl)amide (FSA–) has attracted attention among various ILs, because BMPFSA shows a relatively low viscosity. The SEI formation on a Pt electrode in 0.5 M LiFSA/BMPFSA was investigated by the redox reaction of ferrocene (Fc) and ferrocenium (Fc+) as a redox probe[1,2]. The SEI formation affected the electron transfer rate of Fc+/Fc and was promoted by the interaction of Li+ and FSA–. Furthermore, the breakdown of the SEI formed in 2.9 M LiFSA/BMPFSA was confirmed by the redox probe method, suggesting that the SEI can be considered as a viscous and gelled layer formed by the formation and diffusion of the decomposition products dispersed and/or dissolved in the IL[3].

In the present study, the SEI formation in 0.5 M LiFSA/BMPFSA was investigated by using different redox probes. The redox reactions of some metallocenes and organic compounds on a Pt electrode were investigated by cyclic voltammetry in BMPFSA and 0.5 M LiFSA/BMPFSA. The potential was measured against a Ag|Ag(I) reference electrode, of which the potential was 0.39 V vs. Fc|Fc+[4]. Cyclic voltammograms were taken after holding the electrode at potentials ranging from –0.9 to –1.5 V at 0.1 V intervals for 1 hour. The cyclic voltammograms were uncharged in BMPFSA, indicating that BMPFSA was stable in the potential range and that the redox reactions were not affected by a change in the structure of the electric double layer. On the other hand, peak shifts due to a decrease in the electron transfer rates were observed in the presence of Li+ at the potentials more negative than –1.1 V, indicating that the SEI formation promoted by the interaction between Li+ and FSA– affects the redox reactions not only of mettallocenes but also of organic compounds that undergo outer sphere electron transfer reactions.

References

[1] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 169, 076509 (2022).

[2] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 056504 (2023).

[3] S. Okazaki, N. Serizawa, and Y. Katayama, Electrochemistry, 92, 043006 (2024).

[4] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 046504 (2023).
Electrochemical Oxygen Evolution in Chloride Melts Using Co-Based Oxide Electrodes
Authors: Tanaka Seiya , Suzuki Yuta , Fukunaka Yasuhiro , Goto Takuya
Published: December 2024

Carbon decomposition by molten salt electrolysis has been researched for achievement of carbon negative emissions. Carbonate ions, which are derived from carbon dioxides and oxide ion in the molten salts, are reduced into carbon and oxide ions are produced at cathodes. Oxygen gas is generated from the produced oxide ions at anodes. For realizing the electrochemical carbon decomposition process, development of inert anode is essential task. In the previous research, various materials of metal, cermet and metal oxide have been tested for inert anodes to obtain low corrosion rate and high current density in electrochemical oxygen evolution. Especially, conductive oxides are expected to have both of high electrical conductivity and high corrosion resistance to produced oxygen.

In this study, we report the characteristics of Co-based oxide anodes for oxygen evolution in chloride melts. Co3O4 is one of the representative conductive oxides, which have conduction characteristic. In the experiments of molten chloride containing oxide ions at a temperature over 600℃, the cyclic voltammograms with a prepared Co3O4 anode were measured. The results show drastically increases of current density at 2.9 V vs Ca(Ⅱ)/Ca, which was approximately same to the oxygen evolution potential estimated from thermodynamic calculations. The corrosion behaviors of Co-based anodes will be discussed from the results of long-time electrochemical operation and chemical analysis using XRD, SEM, EDs, and ICP-AES analysis.
The Role of Asymmetry of Perfluoro anion in Ionic Liquids: From Basic Physical Properties to the Application in Lithium Batteries
Authors: Matsumoto Hajime , Kubota Keigo , Sano Hikaru
Published: December 2024

From the late 1990s, room temperature molten salts composed of stable perfluoro anion became known as ionic liquids and have been widely recognized and applied in various fields of chemistry for almost three decades. Our research focuses on the use of aliphatic quaternary ammonium cations (AQA) as electrolytes for lithium secondary batteries, which possess unique properties of non-volatility, non-flammability and relatively wide electrochemical window that cannot be achieved with conventional electrolytes. To improve battery performance by reducing the internal resistance of the battery system, we investigated various perfluoro anion as shown in Figure 1. From these studies we concluded that the rate characteristics of lithium secondary batteries with ionic liquids depend not only on viscosity, which governs the diffusion of Li+, but also on the chemical structure of the perfluoro anion, which govern the interaction between Li+ and the anions.1)-3)

On the other hand, through these studies, we found that the asymmetry of the anion structure 4)-6) and the ether oxygen in the anion side chain7) have significant effects on thermal and transport properties of the ionic liquid, similar to the asymmetry of the cation represented by 1-ethyl-3-methylimidazolium and the ether oxygen in the side chain represented by N,N-dimethyl-N-ethyl-N-(2-methoxyethyl)ammonium. The most striking results are obtained by lithium (fluorosulfonyl) (trifluorosulfonyl) amide (LiFTA)8), which exhibits a relatively low melting point (T
m
= 100 °C) among the Li salts and has applications in battery electrolytes 8) and unique electrochemical properties9).

Here, we would like to show the importance of developing new anion species that give rise to novel ionic liquids and alkali metal salts based on our results.

1) H. Matsumoto, Y. Miyazaki, and H. Ishikawa, Japanese Patent Application (1998).

2) H. Matsumoto, “Electrochemical window of Room Temperature Ionic Liquids”,Electrochemical Aspects of Ionic Liquids (Ed. H. Ohno), Wiley (2005).

3) H. Matsumoto, Recent advances in Ionic Liquids for Lithium Secondary Batteries: Modern Aspects of Electrochemsitry No.58,: Electrolytes for Lithium and Lithium-Ion Batteries, Eds. T. R. Jow, K. Xu, O. Borodin, and M. Ue, chapter 4, Springer, 2014.

4) H. Matsumoto, H. Kageyama, and Y. Miyazaki, Chem. Commun., 1726 (2002).

5) H. Matsumoto, H. Sakaebe, and K. Tatsumi, J. Power Sources, 146(1–2), 45 (2005).

6) H. Matsumoto, N. Terasawa, T. Umecky, S. Tsuzuki, H. Sakaebe, K. Asaka, and K. Tatsumi, Chem. Lett., 37(10), 1020 (2008).

7) Terasawa, S. Tsuzuki, T. Umecky, Y. Saito, and H. Matsumoto, Chem. Commun., 46(10), 1730 (2010).

8) Kubota, and H. Matsumoto, J. Phys. Chem. C, 117(37), 18829 (2013).

9) H. Sano, K. Kubota, Z. Shiroma, S. Kuwabata, and H. Matsumoto, J. Electrochem. Soc., 167(7) 070502 (2019).

Figure 1
Melting Behavior and Ionic Conduction of Multicomponent Carbonates Coexisting with Porous Oxides
Authors: Mizuhata Minoru , Wang Jiayue , Sato Shizuku , Chen Xueling , Maki Hideshi , Minamimoto Hiro
Published: December 2024

Multicomponent systems of alkali carbonates indicate high electrical conductivity, high chemical and thermal conductivity, and low viscosity in the medium temperature range around 500°C, and are used as high temperature reaction media, thermocouples, and sensing materials for CO However, in electrochemical reactions, the high reactivity of carbonates is accompanied by the problem of corrosion of electrodes and reaction systems. We have studied ceria-based oxides and zirconia, which have high reactivity through surface treatment of CO2 absorbing media, and have examined the electrical and thermal properties of the composite materials with molten carbonate. Ceria-based oxides have been considered for application in solid oxide fuel cells as solid electrolytes, whereas γ-LiAlO2 has insulating properties and is used as an electrolyte in molten carbonate fuel cells. In this study, lithium carbonate, sodium carbonate, and potassium carbonate are used as the liquid phase, and mono-, binary-, and ternary complex carbonates or carbonates with eutectic compositions are used. The results are summarized on the effect of salt complexation on the improvement of electrical conductivity at low temperature ranges and the lowering of melting points.

The solid phase was obtained by drying three types of γ-LiAlO2 (24.0 m2/g, 10.3 m2/g, 5.4 m2/g) and other various oxides such as α-Al2O3, MgO, ZrO2 etc. at 500°C for 2 hours under nitrogen. Li2CO3, Na2CO3, and K2CO3 were used for the carbonate phase and dried at 200°C for 48 hours under a carbon dioxide atmosphere. Eutectic carbonates were prepared by mixing them to form a eutectic composition. Each oxide powder was mixed thoroughly in a mortar to form carbonate at a given volume ratio. The sample was formed by pressurization and sintered at 500°C for 1 hour to obtain a tablet for the measurements of ionic conduction and thermal analysis.

As shown in Figure 1, the activation energy of electrical conductivity increased near the solid phase in all cases. The range of influence from the solid phase decreased significantly with increasing carbonate polymorphism: 40 nm for the mono-salt system, 10 nm for the binary system, and about 2 nm for the ternary system. These melting point drops are also affected by the solid phase, but the effect of the distance from the solid phase is not so great. In the vicinity of the solid phase, the effect of the solid phase on ionic conduction is not as strong as that on the phase change, and the more numerous ions move, the less affected by the solid phase the system is. In this presentation, we will discuss the influence of the solid phase from a viewpoint of thermodynamics.

Fig.1 Variation of ΔE
a with apparent average thickness for various carbonates /inorganic powders coexisting systems. Carbonates: (a)Li2CO3, (b) (Li0.52Na0.48)2CO3, and (c) (Li0.435Na0.315K0.25)2CO3.

Figure 1
Insight into Modulation of Ionic Liquids for Li-Ion Batteries: Unprotected Cation
Authors: Hwang Jinkwang , Zhang Shaoning , Wu Shengan , Matsumoto Kazuhiko
Published: December 2024

Sulfonylamide-based ionic liquid electrolytes have shown promising physiochemical and electrochemical properties for secondary battery systems.[1-3] Recently, highly Li-concentrated IL electrolytes have exhibited wide electrochemical stability windows, stable solid electrolyte interphases, and enhanced Li+ transport properties.[4,5] However, a significant challenge lies in the uncontrollably large irreversible capacity of negative electrodes attributed to the emergence of "unprotected organic cations" in ionic liquid electrolytes, leading to unfavorable decomposition. This results in a high irreversible capacity and a gradual decrease in the initial Coulombic efficiency of graphite electrodes.[6]

In this presentation, we will delve into detailed physicochemical analyses and computational studies aimed at elucidating the causes behind the weakened ionic interactions between the organic cation and the [FSA]− anions based on Li
x
[C2C1im]1-x
[FSA] ([FSA]– = bis(fluorosulfonyl)amide and [C2C1im]+ = 1-ethyl-3-methylimidazolium) ionic liquid. Additionally, we will discuss the interaction facilitated by high donor number anions like [OTf]− (trifluoromethanesulfonate), which are suggested to strengthen interactions between the [C2C1im]+ cation and the [FSA]− anion.

Our series presentation, titled "Insight into Modulation of Ionic Liquids for Na-Ion Batteries: Cation Modification”, explores the effects of cation structure modification on the coordination environment of ions in sodium systems.
Synthesis and Characterization of Dicationic Ionic Liquids with the Difluorophosphate Anion
Authors: Kamada Kentaro , Nokami Toshiki , Inui Naoki , Nakajima Hideto , Nishimoto Kohei , Hwang Jinkwang , Matsumoto Kazuhiko
Published: December 2024

Dicationic ionic liquids (DILs) can be diversely designed by tuning spacer and cationic-center structure. Their features possibly superior to conventional ionic liquids include thermal stability, wide potential window, and high Li ion transference number, which make them good electrolyte candidates for secondary batteries. However, there are few reports of DILs and many unknown factors about the relationship between their structure and physical properties.

Although Li[PO2F2] is known as an additive in lithium secondary batteries that improves the negative electrode performance, [1] PO2F2
- itself forms ionic liquids with a variety of onium cations. [2] In this study, we attempted syntheses of DILs with PO2F2
-, especially the ones with ether oxygen in the spacer and evaluated the physical properties of the resulting DILs.

The synthesis of DILs was carried out in three steps. Initially, ethylene glycol was reacted with paraformaldehyde and trimethylsilyl chloride in dichloromethane at room temperature to prepare 1,2-bis(chloromethoxy)ethane. In the second step, dihalide reacted with two equivalents of amines at room temperature and converted to the corresponding chloride salts. Finally, the chloride salts and K[PO2F2] were reacted in dichloromethane at room temperature to exchange anions.

According to the results of differential scanning calorimetry, the dication salts with ether spacer exhibit lower melting points than the corresponding dication salts without ether spacer owing to the flexibility around the ether group. Comparison of densities between pyrrolidinium- and linear alkylammonium-based DILs revealed the higher density of the former salt, which arises from the rotational freedom of the alkyl chain in the latter. The higher viscosity of the DIL with BF4
- than that of the DIL with PO2F2
- is due to the high dipole moment and thus polarity of PO2F2
- consisting of two oxygen and two fluorine atoms. High ionic conductivity is an important factor as electrolyte. The ion conductivity of the DIL with PO2F2
- is higher than that of the DIL with BF4
-, which implies the potential of PO2F2
- DILs in battery applications.

References:

1) G. Yang, J. Shi, C. Shen, S. Wang, L. Xia, H. Hu, H. Luo, Y. Xia, Z. Liu, RSC Adv. 7, 26052 (2017).

2) K. Matsumoto, R. Hagiwara, Inorg. Chem. 48, 7350 (2009).
Linear Ether-Based Molten Li Salt Solvate Electrolytes for Li-Metal Batteries
Authors: Ueno Kazuhide , Ishikawa Toru , Haga Shohei , Shigenobu Keisuke , Sudoh Taku , Tsuzuki Seiji , Shinoda Wataru , Dokko Kaoru , Watanabe Masayoshi
Published: December 2024

Li metal batteries have attracted much attention as the next-generation rechargeable batteries owing to the exceptionally high theoretical capacity (3860 mAh g⁻¹) and the lowest electrode potential of Li metal electrode. Molten Li salt solvate electrolytes or highly concentrated electrolytes (HCEs) are an emerging class of electrolytes having a similarity to ionic liquids (ILs) in high ionic nature, and indeed some of which are found to behave like an IL.1 This type of the electrolytes have attracted considerable attention as prospective candidates for electrolyte materials in future Li metal batteries owing to their favorable properties both in the bulk and at the electrochemical interface. In this study, linear ether-based molten Li salt solvates were investigated for potential effects of weakly coordinating linear ethers on transport properties and battery performance. We focused on the electrolytes using lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) or lithium bis(fluorosulfonyl)amide (LiFSA) as the salt and linear chain monoethers such as methylpropyl ether (MPE), n-butylmethyl ether (BME), and ethyl propyl ether (EPE) as the solvent for lithium-sulfur and lithium metal batteries. Owing to the low lithium polysulfide solubility, low viscosity, relatively high ionic conductivity, high Li ion transference number, high reductive stability, and low specific gravity, all of which are favorable for achieving high-energy density batteries, linear ether-based molten Li salt solvates were found to be effective electrolytes. The correlation between Li ion solvation and ionic transport properties of the linear ethers with different alkyl chain length were further studied to optimize the electrolyte compositions. The chemical structure of the ethers had a strong impact on the Li ion coordination structure and ionic conductivity: the monomethyl ether such as MPE and BME showed more-pronounced Li ion coordination and higher ionic conductivity whereas steric hinderance of longer alkyl chains in ethers with longer alkyl chain length such as ethyl propyl ether (EPE) resulted in lower solvation number, enhanced ion pairing and lower ionic conductivity. The improved Li ion transport property of the linear ether-based electrolytes led to the better rate performance. Furthermore, a pouch-type cell demonstrated an energy density exceeding 300 Wh kg-1 under lean electrolyte conditions.2

Shigenobu, T. Sudoh, J. Murai, K. Dokko, M. Watanabe, K. Ueno, Chem. Rec., 2023, 23, e202200301.

Ishikawa, S. Haga, K. Shigenobu, T. Sudoh, S. Tsuzuki, W. Shinoda, K. Dokko, M. Watanabe, K. Ueno, Faraday Discuss., 2024, Accepted Manuscript. DOI: 10.1039/D4FD00024B
Two-Dimensional, Multi-Reaction, and Multi-Species Porous Electrode Modeling of Metal Oxide Electroreduction with Applications in Nuclear Fuel Reprocessing and Iron Oxide Reduction
Authors: Kellamis Christian John , Sinclair Nicholas Scott , Kersten Bethany , Hawthorne Krista , Ruehl Matthew , Akolkar Rohan
Published: December 2024

Many electrochemical processes involve the reduction of a porous solid metal oxide into pure metal such as the Fray-Farthing-Chen (FFC) Cambridge process 1 for titanium and ULCOWIN 2 process for iron. With optimal electrolysis cell designs, these processes would produce metal efficiently without energy losses to parasitic side reactions. Predictive modeling of the reaction rate (current) distribution underlying these processes can allow for increased energy efficiency and higher metal electrowinning yields. This would be beneficial to the fields of nuclear fuel reprocessing and sustainable metals production, which utilize electro-reduction of uranium oxides and iron oxides, respectively. This presentation will cover the development of a two-dimensional, multi-reaction model that simulates the current distribution during oxide reduction and models the potential profiles of both the metal oxide phase and the liquid electrolyte phase within the oxide pores. The model applies the concepts of porous electrode theory developed by Newman and Tobias 3 but modifies it to incorporate multiple reactions.4, 5 The model is then applied to uranium oxide reduction in a molten salt electrolyte, and aqueous processing of iron oxide ores for iron electrowinning. This modeling study helps establish the main controlling parameters for the current distribution uniformity, i.e., the solid electronic conductivity of the oxide phase, the liquid electrolyte conductivity of the molten (or aqueous) electrolyte, the tortuosity and porosity of the porous oxide matrix, and the exchange current densities of the metal oxide and the liquid electrolyte reactions. Experimentally measured current distribution profiles on a porous electrode comprising iron oxide particles will be shown as validation of model findings.

References

G. Z. Chen, D. J. Fray, and T. W. Farthing, Nature,
407 (6802), 361-364 (2000).

M. Abdul Quader, S. Ahmed, S. Z. Dawal, and Y. Nukman, Renewable and Sustainable Energy Reviews,
55 537-549 (2016).

J. S. Newman and C. W. Tobias, Journal of The Electrochemical Society,
109 (12), 1183 (1962).

D. R. Baker and M. W. Verbrugge, Journal of The Electrochemical Society,
165 (16), A3952-A3964 (2018).

D. R. Baker, M. W. Verbrugge, and W. Gu, Journal of The Electrochemical Society,
166 (4), A521-A531 (2019).
Electric Double Layer Modification Induces Progressive Nucleation and Nanoscale Zinc Deposition for Aqueous Zinc Metal Batteries
Authors: Wang Ziqing , Mullins Charles Buddie
Published: December 2024

Aqueous zinc metal batteries have been regarded as a promising alternative to conventional lithium-ion batteries for grid-scale energy storage due to their high safety and low cost.1 However, the formation of zinc dendrites on the zinc metal surface during electrodeposition significantly deteriorates the sustainability and stability of aqueous zinc metal batteries.2 Hence, it is crucial to reduce the zinc dendrites and other side reactions and control the uniform zinc deposition on the electrode surface by regulating the electrolyte-electrode interface. In this work, we introduce a tiny amount of sodium-difluoro(oxalato)borate (NaDFOB) into the ZnSO4 electrolyte to modify the zinc deposition. The electrochemical tests and density functional theory simulations demonstrate that the DFOB− ions adsorb on the zinc electrode surface to construct a water-poor electric double layer. The molecular dynamics results confirm the occupation of DFOB− ions in the electric double layer. Because of the specific adsorption on the zinc metal surface, DFOB− ions not only suppress the aggregation of deposited zinc to form dendrites but also promote the unique progressive nucleation process. Through scanning electron microscope, the formation and growth of nanoscale zinc nuclei can be observed in the electrolyte with the addition of NaDFOB. Eventually, the early-stage nanoscale nuclei result in ultra-uniform zinc growth. Furthermore, the decomposition of adsorbed DFOB− ions yields the formation of an inorganic compound-rich solid electrolyte interphase, which effectively enhances the reaction kinetics on the electrode surface and reduces the parasitic reactions. As a consequence, the introduction of NaDFOB realizes high reversibility of zinc plating/stripping behavior in Zn/Cu asymmetric cells with a Coulombic efficiency of 99.3% and in Zn/Zn symmetric cells with a cycling life for over 500 hours under a high current density of 5 mA cm−2. Additionally, the full cells employing Na0.33V2O5 cathode materials exhibit a promising capacity of 200 mAh g−1 and long-term stability for over 400 cycles. The introduction of DFOB− anions provides a facile strategy to regulate electrodeposition in aqueous zinc metal batteries by reconstructing the electric double layer and regulating nanoscale zinc nuclei.

References:

S. Liu et al. Angew. Chem. Int. Ed., 2024, e202400045.

T. Zhang et al. Energy Environ. Sci., 2020, 13 (12), 4625-4665.

Figure 1
Theoretical View on Alternatives to Oxygen Evolution Reaction Processes
Authors: Basera Pooja , Jiang Chenyu , Ablid-Pedersen Frank , Manthiram Karthish , Bajdich Michal
Published: December 2024

Our recent survey of oxygen bonding strength in the transition metal oxides revealed a broad range of reactivities resulting in a V-shape type behavior related to filling anti-bonding states. For metals with filling close to d0 to d10, the oxygen reactivity is generally weak [1]. While oxygen evolution reaction (OER) is well known for metal-oxides with moderately bonded oxygen such as in IrO2 and RuO2, chemistry of a weakly bonded metal-oxides is significantly less explored. At the same time, photo-electrochemical solar-fuel devices, such as one developed at Liquid Sunlight Alliance (LiSA), would strongly benefit from anodic reactions which are alternative to OER as a way to produce anodic products with added value and/or having lower onset potentials.

Very promising reactions currently being explored are water oxidation to peroxide, epoxidation of light olefins [2] and alcohol oxidation reactions [3]. In our theoretical analysis, we computationally re-evaluate this weakly bonded region and identify the switch from oxo bonded species species to peroxo one, previously known to occur in systems such TiO2. We compute the overall energetics of the above reactions and analyze which reactive oxygen species is preferential for each of the alternative reactions. We conclude with discussion of fundamental feasibility and limitations of alternative anodic reactions to OER.

This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266.

[1]. Comer, B. M.; Bothra, N.; Lunger, J. R.; Abild-Pedersen, F.; Bajdich, M.; Winther, K. T. Prediction of O and OH Adsorption on Transition Metal Oxide Surfaces from Bulk Descriptors. ACS Catal. 2024, 5286–5296.

[2] Chung, M.; Maalouf, J. H.; Adams, J. S.; Jiang, C.; Román-Leshkov, Y.; Manthiram, K. Direct Propylene Epoxidation via Water Activation over Pd-Pt Electrocatalysts. Science 2024, 383 (6678), 49–55. https://doi.org/10.1126/science.adh4355.

[3] Wei, L.; Hossain, M. D.; Boyd, M. J.; Aviles-Acosta, J.; Kreider, M. E.; Nielander, A. C.; Stevens, M. B.; Jaramillo, T. F.; Bajdich, M.; Hahn, C. Insights into Active Sites and Mechanisms of Benzyl Alcohol Oxidation on Nickel–Iron Oxyhydroxide Electrodes. ACS Catal. 2023, 13 (7), 4272–4282.
Highly Sensitive Detection of Redox Species by Current Amplification Using a Thin-Layer Reactor with Boron-Doped Diamond Electrode
Authors: Asai Kana , Otake Atsushi , Einaga Yasuaki
Published: December 2024

In electrode reactions, an electric double layer exists in the nearest region of the electrode surface. And the next layer is a diffusion layer where a concentration gradient is generated by mass transport by diffusion. In a conventional electrochemical cell, a bulk layer exists between the working and counter electrodes. The rate of electrode reaction is limited by the electron transfer at electrode/electrolyte interface as well as the mass transport in the bulk layer. In this study, the thin-layer reactor was fabricated using diamond electrodes with an inter-electrode distance on the order of micrometers. Using the thin-layer reactor, we investigated the reaction mechanism and highly sensitive detection of redox species. Cyclic voltammograms (CVs) in ferrocyanide ([Fe(CN)6]4-) solution showed increasing of oxidation current. After that, the oxidation current decreased in the conventional reactor. On the other hand, the thin-layer reactor did not show the current decreasing but the steady current at the oxidative potential(Fig 1). The calibration curve obtained with the thin-layer reactor confirmed the highly sensitive detection of ferrocyanide ([Fe(CN)6]4-). In the case of a conventional reactor, the oxidation current was decreased due to lack of supply of Fe (Ⅱ) species. On the other hand, in the case of the thin-layer reactor, the steady current was observed due to a three-step cycle of (1) consumption of Fe (Ⅱ) species and formation of Fe (Ⅲ) species at the working electrode, (2) regeneration of Fe (Ⅱ) species at the counter electrode, and (3) resupply of Fe (Ⅱ) species to the working electrode, cause the steady-state current and highly sensitive detection. Comb array electrodes are reported as an example of highly sensitive detection of redox species. The proximity of the working and counter electrodes is known to contribute the current amplification. In this study, the thin-layer reactor is expected to exhibit even higher detection sensitivity than a comb electrode because it efficiently utilizes the amplification reaction at the counter electrode by completely eliminating the bulk layer. Another advantage of the thin-layer reactor is the simple fabrication with large area electrodes compared with the comb array electrodes. In addition, electrochemical behavior with different counter electrode materials is discussed.

Figure 1
Oxidative Desorption Behavior of Sulfur Species from Pt and Pt Based Alloy Single Crystal Surfaces
Authors: Morooka Tetsuro , Aoki Makoto , Nakanishi Takuya , Ishikawa Atsushi , Masuda Takuya
Published: December 2024

Pt and Pt-based alloys are the most widely used electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs) because of their very high hydrogen oxidation and oxygen reduction activities. However, trace amounts of S species in hydrogen fuel and air, especially in long tunnels and volcanic areas, often strongly adsorb on the Pt and Pt-based alloy surfaces, resulting in reduced electrochemically active surface area (S poisoning). Thus, understanding of adsorption/desorption behavior of S species at Pt and Pt-based alloy surfaces is very important to mitigate such S poisoning. In the present study, oxidative desorption behavior of S species from well-defined Pt and Pt-based alloy single crystal surfaces in acidic aqueous solutions were studied by electrochemical measurements, x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation.

Pt and Pt-based alloy single crystal surfaces were annealed by induction heating method [1, 2, 3] at various temperatures for 1 h under the flowing of Ar and H2 mixed gas, followed by cooling under the Ar and H2 flow for 7 min. The surfaces were then immersed in an aqueous solution of 1 mM Na2S for 1 h to yield S-adsorbed surfaces. After rinsing with water, electrochemical measurements were carried out in an aqueous solution of 0.1 M HClO4, followed by XPS measurements.

Bare Pt and Pt-based alloy single crystal surfaces showed characteristic current responses corresponding to adsorption/desorption of hydrogen and hydroxyl species as previously reported. After immersing in the 1 mM Na2S solution, those characteristic current responses completely disappeared due to the blocking of adsorbed elemental S species as evidenced by XPS. However, those characteristic current responses gradually recovered by repeating the potential cycles in the potential range between 0 V and 0.8 V or more positive, due to the oxidative desorption of S species. The recovery factor significantly depends on the face orientation, alloying foreign metal and surface modification. Among the Pt(111), Pt(110) and Pt(100) surfaces, Pt(111) surface showed the highest S oxidation capability. The S oxidation capability was further accelerated by alloying with several transition metals and coating with metal oxides. The details will be discussed.

References

[1] T. Masuda, S. Faridah, P. Singh, H. Naohara, K. Uosaki, Journal of Physical Chemistry C, 2013, 117, 15704-15709.

[2] T. Masuda, H. Fukumitsu, T. Kondo, H. Naohara, K. Tamura, O. Sakata, K. Uosaki, Journal of Physical Chemistry C, 2013, 117, 12168-12171.

[3] R. Devivaraprasad, T. Masuda, Langmuir, 2020, 36, 13793-13798.
Up-Scaling Solar Hydrogen Production: Development and Demonstration of Photoelectrochemical Reactors
Authors: Creasey George Henry , Moelich Arend W , Rodriguez Acosta John Wilman , Shalvey Thomas P , Garcia-Osorio Dora Alicia , McCallum Tristan W , O'Neil Liam , Zhu Jinjie , Halder Siddharth , Ai Ray , Major Jon , Cowan Alexander J , McGregor Craig , Kafizas Andreas G , Hankin Anna
Published: December 2024

For commercially viable photoelectrochemical hydrogen production, considerable progress must still be made in the development and demonstration of up-scaled devices. The development of low cost and scalable photoelectrode materials that can harness light over a wide range of wavelengths, catalyse water oxidation/reduction, and are chemically, (photo)electrochemically and mechanically robust, remains a bottleneck on which research efforts are largely focused. The design and demonstration of up-scaled devices is equally important and must be addressed in parallel, to ensure material compatibility with the systems they will be used in. The constraining factors that must be considered in device design include: (i) electrode scale-up; (ii) modes of illumination; (iii) current distribution (and associated losses); (iv) the utilisation of a membrane; (v) heat and mass transport.[1] I will present the steps we have taken to address these.

Our up-scaled photoelectrochemical reactor has an irradiance area of 60 cm2 and is capable of splitting water and oxygen using only photon energies. The reactor was irradiated outdoors with natural sunlight during March, April and May 2024 at Stellenbosch University, South Africa (33.93° S, 18.86° E), while mounted on a 2-axis tracking platform. Light was directed laterally both into the (photo)cathode and photoanode compartments, which were separated by an ion-permeable membrane.

The reactor was operated in two modes:

Photoelectrochemical (PEC), with an FTO|WO3|BiVO4|NiFeOx photoanode and a FTO|Au|Sb2Se3|CdS|TiO2|Pt photocathode[2];

PV-assisted photoelectrochemical (PV-PEC), with an FTO|WO3|BiVO4|NiFeOx photoanode, Ni cathode and externally mounted c-Si PVs.

Two modes of illumination were compared:

(i) Direct irradiation, through the use of mirrors;

(ii) Concentrated irradiation (up to a factor of five), through the use of linear Fresnel lenses coupled with stepped Al waveguides.

This research seeks to elucidate challenges of developing up-scaled materials for water splitting, to facilitate the pathway to commercially viable photoelectrochemical hydrogen production. I shall discuss the experimental results from reactor testing, the performance under various modes of irradiation, and the effects of electrode materials, geometries and relative configurations within the reactor on its design.

Refs:

[1] A review of inorganic photoelectrode developments and reactor scale-up challenges for solar hydrogen production, Adv. Energ. Mater., 2021, 11, 2003286.

[2] Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting, Nat. Commun., 2020, 11, 861.

Figure 1
Solar-Driven Polyvinyl Alcohol Remediation: Black Phosphorus Quantum Dot Sensitized g-C3N4 Photocatalyst Vs. H2 Evolution in Photocatalytic Fuel Cells
Authors: Sun Qiong , Sun Likun , Zhang Baoning , Dong Lifeng
Published: December 2024

In response to polyvinyl alcohol (PVA) waste pollution, we developed a composite photocatalyst by sensitizing g-C3N4 with black phosphorus quantum dots (BPQDs) using a simple mechanical stirring technique. Both g-C3N4 and BPQDs are inorganic semiconductors, enabling efficient photoinduced charge transfer. Leveraging the adjacency of C, N, and P elements in the periodic table facilitated the formation of P-N or P-C bonds, resulting in uniform BPQD decoration on two-dimensional layered g-C3N4, with an average size of 2.2 nm. Under solar light simulator irradiation for 20 minutes, the composite photocatalyst exhibited significantly enhanced photocatalytic activity, increasing PVA degradation efficiency from 27.1% (pure g-C3N4) to 85.9%. Experimental observations and theoretical calculations suggest the establishment of a Z-scheme route at the g-C3N4/BPQDs interface, facilitating photoinduced electron transfer from g-C3N4 to BPQDs, leading to augmented carrier generation and separation, reduced charge-transfer resistance, and accelerated PVA degradation. The proposed composite photocatalyst holds promise in addressing PVA pollution and promoting environmental sustainability.

Additionally, in a dual-chamber photocatalytic fuel cell setup, simultaneous degradation of PVA and hydrogen evolution were achieved, employing commercial P25 as the photoanode and Ag@Fe2O3 nanoparticles as the cathode. Moreover, the feasibility of a Fenton-like reaction at the cathode, utilizing Fe2+ ions and pumped O2, was demonstrated. The effects of different cathode materials, PVA types, and pH values on device performance were assessed, with quenching tests highlighting the pivotal roles of h+ and OH· radicals in PVA degradation. The device's long-term stability was established through cycling experiments.
(Invited) Electrocatalytic Ammonia Splitting to Enable the Nitrogen Economy
Authors: Hamann Thomas
Published: December 2024

Synthesis of NH3 using the most abundant renewable energy resources (sun/wind), and abundant chemical feedstocks on Earth (H2O and N2) via the energy efficient, large-scale and cost-effective Haber-Bosch (HB) process enables the possibility of producing carbon-free, high energy density liquid fuel on the TW scale. The HB reaction is almost thermoneutral, which means hydrogen’s intrinsic energy is largely retained in ammonia, making NH3 likely the best candidate for storing and transporting renewable H2. The conversion of NH3 to electricity via a direct ammonia fuel cell or back to H2 via electrolysis has received little attention until very recently, however, and is primarily limited by the ammonia oxidation half reaction. This talk will present our recent investigation of homogeneous electrocatalysts to drive the NH3 splitting reaction at room temperature and ambient pressure. Our recent efforts aimed at understanding the mechanism of the ammonia oxidation reaction with [Ru(tpy)(dmabpy)NH3]2+, using a variety of spectroscopic (NMR and optical) and electrochemical methods will be presented. Interestingly, reactions [Ru(tpy)(dmabpy)NH3]3+ with various Lewis bases are shown to trigger a catalytic reaction which results in formation of a characterized N2-bridged dimer intermediate species. Alternative ammines coordinated to the Ru center are also oxidized to form surprising highly oxidized products. The effect of solvent on the overpotential and catalysis will be discussed as well as preliminary results of next-generation Ru and Os catalysts.
(Invited) Photocatalytic Chemical Transformation in Dye-Sensitized Photoelectrochemical Cells for Lignin Valorization
Authors: Lee Jeong Kyeong , Park Seongsu , Leem Gyu , Kwon Tae_Hyuk
Published: December 2024

Lignin is a plentiful natural aromatic resource, offering potential as a feedstock for alternative fuels and chemicals.1 Dye-sensitized photoelectrochemical cells (DSPEC) have been used to C-C bond cleavage of lignin to earn valuable aromatic compounds under mild conditions, low applied bias, and room temperature.2 An oxoammonium, generated through the oxidation of an aminoxyl radical mediator, facilitates selective reactions by oxidizing benzylic alcohol or aliphatic alcohol groups following C-C bond cleavage, lowering the bond dissociation energy.3 Activation of the oxoammonium is crucial for efficient catalytic reaction, achieved through hole transfer from the oxidized dye under illumination. The effectiveness is measured by photocurrent, reflecting the oxoammonium generation driving force, which is related to the Gibbs free energy between the aminoxyl radical mediator and the HOMO energy level of the sensitizer. Therefore, elucidating the impact of organic sensitizer with D-π-A structures on oxoammonium generation driving force is vital for lignin oxidative cleavage reaction. We adjusted the HOMO to achieve close to zero, negative, and positive oxoammonium generation driving forces by modifying triphenylamine based donor structure with substituents such as -H, -OCH3, and -carbazole. The resulting photocurrent density, interfacial activity, and the yield of the lignin degradation products were proportional to the driving force, indicating the importance of the sensitizer design in controlling the oxidative cleavage reaction.

Figure 1
(Invited) Behaviors of Photogenerated Charge Carriers at the Defects on Photocatalysts
Authors: Yamakata Akira
Published: December 2024

Defects in powder photocatalysts determine the photocatalytic activity. The addition of defects sometimes enhances the activity, but sometimes decreases it. However, the factors determining the difference between these cases have not been fully elucidated yet. Herein, we investigated the effects of oxygen vacancies on several photocatalysts using time-resolved visible to mid-IR absorption spectroscopy. The detailed results will be presented at the conference.