bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrowinning of Light Metals from Molten Salts Electrolytes
Authors: Haarberg Geir Martin 
Published: December 2024

Light metals such as lithium, sodium, potassium, magnesium and aluminium are produced by molten salts electrolysis. Aluminium is by far the largest in terms of production volumes. Magnesium is currently produced by silicothermic reduction of MgO according to the Pidgeon process. Titanium is also regarded as a very attractive light metal with excellent properties. The current Kroll process is energy intensive and requires lots of work as well as low productivity. Ongoing research focuses on developing a process based on electrolysis in molten salts.
The main reason for large carbon footprint during electrowinning of metals from molten salts is the source of electricity due to the fact that China is the largest producer where generation of electricity is based on coal. In the Hall-Heroult process for producing aluminium the use of carbon anodes is an additional important cause for increased CO2 emissions. The use of carbon anodes also leads to the formation of perfluoro carbon (PFC) gases CF4 and C2F6 which are powerful greenhouse gases. The search for an inert oxygen evolving anode has been going on for many decades and if successful it will improve the carbon footprint significantly. The possibility to use alloys with iron, nickel and copper has been popular recently. Magnesium is produced by the Pidgeon process which is based on silicothermic reduction of MgO. However, electrolysis in molten chloride electrolytes using MgCl2 as feedstock used to be the main process for producing magnesium for many years until around 2000. Electrowinning is better in terms of environmental issues and carbon footprint but the Pidgeon process is more profitable. The production processes for alkali metals by electrolysis in molten chloride electrolytes may be improved by using alkali metal oxides as raw materials and inert oxygen evolving anodes, where tin oxide is a strong candidate and is commercially available. Electrolysis to produce titanium is very challenging mainly because of the existence of several stable valencies of dissolved titanium species. Electrodeposition of titanium based alloys by co-deposition of alloying elements may be a new and interesting alternative.
Oxygen Evolution Behavior of Ni-Containing Alloy Electrodes in NaOH–KOH Hydrate Melt
Authors: Kawaguchi Kenji , Nohira Toshiyuki 
Published: December 2024

Hydrogen is expected to be the next-generation energy carrier with zero CO2 emissions. Alkaline water electrolysis (AWE) is one of the methods for hydrogen production; however, improving its energy efficiency is a challenge. We are currently developing a highly efficient water electrolysis using hydroxide hydrate melts at 150–200°C [1,2]. Recently, we reported that the overpotential for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a Ni electrode in a NaOH–KOH hydrate melt at 200°C under atmospheric pressure was significantly reduced compared to a 30 wt% KOH aqueous solution at 80°C, which is a typical electrolyte for conventional commercial AWE [2]. In addition, the OER overpotential was found to be larger than the HER overpotential at the Ni electrode in the NaOH–KOH hydrate melt [2]. In the present study, we investigated the OER behavior of Ni-containing alloys in the NaOH–KOH hydrate melt.
Linear sweep voltammetry was performed in the NaOH–KOH hydrate melt (NaOH:KOH:H2O = 9:61:30 mol%) at 150 and 200°C using a three-electrode cell. Several types of commercially available Ni-containing alloy plates with a flag-shaped and 3 mm diameter were used as the working electrode. A Ni rod was used as the counter electrode. A palladium hydride (Pd–H) electrode was used as the reference electrode and the potential was calibrated with respect to the reversible hydrogen electrode (RHE). All measured potentials were IR compensated. All measurements were performed in stationary electrolytes under Ar gas flow at atmospheric pressure.
Figure 1 shows anodic polarization curves at Ni–Fe and Ni–Cu alloy electrodes in the NaOH–KOH hydrate melt at 150°C. The polarization of Ni–Fe and Ni–Cu alloy electrodes is lower than that of the Ni electrode. In this paper, we will also present the results for other Ni-containing alloys.
A part of this study was supported by Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) from Japan Science and Technology Agency (JST) Grant Number JPMJTR23TB.
[1] K. Kawaguchi, K. Goto, A. Konno, and T. Nohira, J. Electrochem. Soc., 170, 084507 (2023).
[2] K. Goto, K. Kawaguchi, and T. Nohira, Electrochemistry, 92, 043021 (2024).

Figure 1
Study on Ionic Plastic Crystals As Lithium-Ion Electrolytes
Authors: Sugisawa Hiroki , Takahashi Toshifumi , Nakatsuka Emi , Aikyo Hiroyuki , Fukii Kaoru , Kato Masahiko , Satake Kenichi , Hamamura Tomofumi 
Published: December 2024

Ionic plastic crystals (IPC) have a highly symmetrical crystal structure similar to CsCl or NaCl, as a result of utilizing the energy associated with crystal melting for molecular rotational motion [1,2]. The introduction of lithium salt into these materials can realize the lithium-ion electrolytes enhanced conductivity compared to pure plastic crystals [3]. However, this operation concurrently reduces the plastic crystal's melting point, thereby limiting the temperature range existing as an electrolyte [3]. Therefore, this study explores two avenues to discover materials featuring the plastic crystal phase with the broad temperature range and the high ion conductivity.
In the first approach, attention is directed towards the anion structure of lithium salts. Conventionally, the anion of lithium salts is selected to be same with one of the plastic crystals. However, investigating various combinations of plastic crystals and lithium salts holds promise. The second approach is development of additives. Increasing the amount of additives similar to lithium salts causes the disadvantage of narrowing the temperature range of the plastic crystal phase. Therefore, we seek to investigate if this disadvantage can be avoided through anion or additive modification. Detailed findings from these investigations will be reported on the day of the presentation.
[1] J. Pringle, Phys. Chem. Chem. Phys.
15, 1339 (2013).
[2] J. Pringle, P.C. Howlett, D.R. MacFarlanea and M. Forsyth, J. Mater. Chem.
20, 2056 (2010).
[3] M.L. Thomas, K. Hatakeyama-Sato, S. Nanbu, and M. Yoshizawa-Fujita, Energy Adv.
2, 748 (2023).
Online Monitoring of Alkali Chloride Molten Salt Composition, Speciation, and Basicity Using UV-Vis-NIR Absorption Spectroscopy
Authors: Moon Jeremy , Sharpless Laurel , Chidambaram Dev 
Published: December 2024

For molten salt reactors and pyrochemical reprocessing systems, it is vital to monitor the concentration and speciation of U and fission products in the fuel salt as well as the basicity of the salt. We show that NIR spectroscopy allows for better monitoring of actinide and lanthanide fission product concentrations and speciation with greater sensitivity than UV and visible range absorption spectroscopy due to fewer interfering absorption lines, more tractable molar absorption coefficients of transitions present in this range, and less sensitivity to scattering from solid phases suspended in the salt. Additionally, to monitor the basicity of the molten salt mixture, we have explored the use of Pb2+ and Bi2+ as probe ions; shifts in the absorption maxima of their 6s→6p electronic transition are correlated to changes in the Lewis basicity of the molten salt. We show that this optical basicity method is viable in alkali chloride molten salts and may be of use for online monitoring of molten salt chemistry in nuclear molten salt applications.
This work was funded by Department of Energy under award DE-EE0009822
The Specific Adsorption of Chloride Ions from Ionic Liquid
Authors: Siinor Liis , Ers Heigo , Luure August , Leuska Ermo , Pikma Piret 
Published: December 2024

Interactions and processes that determine the characteristics of the electrode–ionic liquid (IL) interface are crucial for developing fundamental understanding and various applications1-2. This implies that the expected progress of electrochemical energy storage devices and other appliances relies on the success of describing these interfacial systems and processes in detail. Various factors define the interfacial properties of any electrode-electrolyte system3. These factors can be roughly divided into 3 groups: electrode-related (the effect of surface structural and electronic properties), electrolyte-related (the chemical composition and/or presence of additives), and external factors (applied potential, temperature, etc.). Numerous well-recognized research groups have described the properties of the electrode-IL interface. The consensus is that ILs form ordered interfacial layers at electrodes, while the interfacial processes are much slower than in other electrolytes4. Despite the consensus, numerous fundamental questions have yet to be answered.
The main aim of this work was to characterize the adsorption of chloride ions from the mixture of two ionic liquids based on the same 1-ethyl-3-methylimidazolium cation5.
Electrochemical impedance spectroscopy and cyclic voltammetry methods have been applied to study the electrochemical characteristics of the interface between Bi(111) and mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and 1-ethyl-3-methylimidazolium chloride (0-2 wt%).
Experimental results show that within the potential region of specific adsorption of Cl–, capacitance (C) values increased significantly compared to neat EMImBF4 and were limited by Gibbs adsorption effect at high Cl– concentration. The equilibration of the interface and the formation of a stable adsorbed layer of Cl– is a lengthy process timewise. The C values decrease in time, reaching a stable value after 36 h. Phase angle values confirmed that the kinetics of these processes is limited by the adsorption kinetic step in a wide range of alternative current frequencies. The findings are supported by in situ STM images, where a highly ordered structure was visualized.
References

Fedorov, M. V. et al., Chem.Rev.114 (5) 2978 (2014).

MacFarlane, D. R. et al., Phys.Chem.Chem.Phys. 12 (8) 1659 (2010).

Trasatti, S. Electrochim. Acta 37 (12), 2137 (1992).

Ers, H. et al., Electrochim. Acta 421, 140468 (2022).

Siinor, L. et al., J. Phys. Chem. C 128, 2722 (2024).

Acknowledgements
This work was supported by the Estonian Research Council Grants PSG249 and PRG676; the European Regional Development Fund under Project TK141 (2014-2020.4.01.15-0011), the Estonian Ministry of Education and Research Project TK210, and by the project “Increasing the knowledge intensity of Ida-Viru entrepreneurship” (ÕÜF12) co-funded by the European Union.
Electrochemical Hydrogen Evolution Using Proton Transport through Graphene Monolayers
Authors: Baranitharan Sekar , Motobayashi Kenta , Ikeda Katsuyoshi 
Published: December 2024

Pursuing sustainable hydrogen, electrochemical Hydrogen Evolution Reaction (HER) is crucial. However, challenges arise during HER, including the dissolution of catalytic materials and the formation of hydrogen bubbles on the electrode surface. Bubbles that evolve at an electrode may result in undesired blockage of the electrocatalytic surface, and ion conducting pathways in the electrolyte resulting energy losses1. Our study addresses this issue using monolayer graphene as a two-dimensional electrode with proton permeability.
A graphene monolayer was synthesized using chemical vapor deposition (CVD) on a copper substrate. The fabrication process involved assembling the graphene monolayer on copper foil with nafion followed by hot pressing at 140°C for 2 minutes under 1.4 MPa pressure. Subsequently, this assembly was floated on Cu etchant (0.2 M (NH4)2S2O8 aqueous solution) facing Cu foil side overnight at 25°C and then rinsed Milli-Q water for several times. Platinum nanoparticles on graphene/nafion membrane was deposited using potential step method2. The electrochemical tests were carried out in 0.5 M H2SO4 vs RHE under argon (Ar) saturation using home-built electrochemical cell designed for proton permeable electrodes as illustrated Fig (a) and Cyclic voltammetry (CV) Fig (b) was performed Pt/Gr/N, Pt electrode at a scan rate of 50 mV/s.
The hydrogen evolution performance of Pt/Gr/N measured in the proton permeable transport configuration in 0.5 M H2SO4 as evidenced by cyclic voltammetry revealing an observed lower overpotential of 17 mV at 10 mA/cm²(Pt-ECSA) suggests that proton transport occurs through the graphene layer, facilitating the hydrogen evolution reaction (HER) in gas phase without the generation of gas bubbles in electrolytes. This leads to minimal H2 reoxidation on Pt, which results in a positive shift in the observed onset potential and higher current density. On the other hand, Pt electrode in the conventional proton diffusion transport configuration exhibited a slightly higher overpotential of 28 mV at the same current density per Pt-ECSA, due to the HER in the solution phase. Indeed, hydrogen oxidation reaction (HOR) during the backward potential scan ofs the CV was observed only in the case of the conventional Pt electrode.
1.Zhang C, Guo Z, Tian Y, et al. Nano Research Energy, 2: e9120063 (2023)
2.Domínguez-Domínguez, et al. J Appl Electrochem 38:259–268 (2008)

Figure 1
Challenges in Accurate Calculation of Electrochemical Reactions Using First Principles Calculations: Water Adsorption on Pt(111) Surface Under Applied Potential
Authors: Shishkin Maxim , Yamaguchi Takeo 
Published: December 2024

Modelling of chemical reactions controlled by an applied external potential could greatly enhance technological developments in the fields like electrochemical synthesis, fuel cells, water electrolysis and etc. Such modelling could be used for in silico search for more active and more stable catalysts, avoiding time consuming and costly experiments. However, a key prerequisite for reliable and successful modelling should be a close agreement between evaluated properties and their experimental observations.
In this presentation the fundamental reaction of water interactions with a surface of Pt electrode is discussed. We chose this reaction as a useful illustrative example where available experimental measurements, such as potentials of water adsorption and dissociation on Pt surface could be directly compared to the modelling for benchmarking of a computational accuracy. Herein, the ability of an employed DFT-based method with implicit model of solution is tested, addressing challenges such as limitations in accurate evaluation of materials work functions, approximate model of solution and difficulties in total energy evaluation under the constant potential.
As a first step, we point out to the problem of employing an experimental range of a potential of the standard hydrogen electrode (SHE), used as a reference in theoretical calculations in view of an inability of DFT to provide sufficiently accurate evaluation of materials work function and hence an operating potential. Secondly, we also show that upon hydration of a Pt surface there exists a peculiar non-monotonic change of a potential upon charging of a slab in contrast to monotonic relation for a clean Pt surface, which we explain by modification of water binding mechanism (presence of a dual charge in certain voltage range) with changing of a charge state of Pt surface (Fig. 1).
To characterise the binding mechanism of a water molecule to Pt(111) surface we analysed the partial density of states, Fukui function and density matrices of p-states of an oxygen atom of a water molecule upon adsorption. Based on our calculations we conclude that greater binding upon application of a higher potential is accounted for by a charge accumulation in the Pt-O interatomic space, in spite of an overall total charge decrease.
In summary our work provides a reliable methodology, that could be applied for analysis of reaction steps of electrochemical reactions on Pt surface under the applied external potential.
This presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Figure 1
Effects of Rb-Based Mixed Fluxes on Surface Crystal Growth of BaTaO₂N and Photocatalytic Activities
Authors: Tashiro Keito , Yamada Tetsuya , Yanagisawa Kazumichi , Tipplook Mongkol , Hayashi Fumitaka , Teshima Katsuya 
Published: December 2024

Photocatalytic water splitting has been actively studied from the viewpoint of environmental issues as a method to produce hydrogen, a clean energy source, without using fossil fuels. Oxynitride BaTaO2N is a visible light responsive photocatalyst and is expected to have high energy conversion efficiency for hydrogen production using sunlight. In a previous study, single phase BaTaO2N crystals were successfully grown by the flux method. However, the maximum activity value is only about 500 µmol/h, which is insufficient to produce enough hydrogen for practical use. One of the reasons for this is unoptimized crystal surface, such as crystal face, and lattice defects. Flux method is known as an effective method to control crystal properties, but single flux is difficult to control these crystal properties at the same time. For example, although RbCl flux can reduce defect density by minimizing elemental contamination of BaTaO2N, it is highly volatile and not effective in controlling the crystal surface. Therefore, we considered the use of multiple fluxes at the same time. This allows appropriate modification of factors related to the flux reaction field, such as viscosity, melting point, and solute-solvent interaction, while avoiding elemental contamination. This leads to flexible adjustment of the crystal growth mode, which we believe will bring crystal growth closer to ideal conditions.
In this study, the effect of multi-flux on the growth mode and photocatalytic properties of BaTaO2N crystals was investigated. As an example, we report the crystal growth of BaTaO2N using mixed fluxes of RbCl, RbBr, and Rb2CO3. A single RbCl flux provided step-terrace surface structure of the BaTaO2N crystal, while an equimolar mixture of RbCl and RbBr resulted in a flatter and more rounded crystal. The visible-light responsive photocatalytic activity of the BaTaO2N crystals obtained with each flux was evaluated. The photocatalytic H2 evolution value of BaTaO2N grown in RbCl-RbBr mixed flux was about 30% of that grown in RbCl flux. This drastic change in activity may be explained by decrease of active crystal surface, including step-terrace one derived from mixed flux reaction field. We are now investigating the effect of step-terrace structure on photocatalytic activity, by tuning the surface structure using the mixed flux species. In the presentation, we will systematically report fine design of crystal growth, photocatalytic activity, and also the contribution mechanism of the mixed fluxes on them.
Acknowledgement
This work was partly supported by the NEDO Green Innovation fund projects, the Strategic Innovation Program (SIP) of the Cabinet Office, and joint research with a company.
Organic π-Conjugated Polymers as a Photoelectrocatalyst for Water-Splitting
Authors: Oka Kouki 
Published: December 2024

Introduction

Hydrogen gas (H2
) is an important chemical feedstock; it is used as a reductant in petroleum refining, ammonia synthesis, the manufacture of stainless steel, and the production of core chemicals (e.g., methanol) and food (e.g., margarine). H2
is also regarded to be a critical and indispensable clean fuel for sustainable energy systems because of its extremely high energy density of 142 kJ g−1 (vs. 44 kJ g−1 for gasoline) and low pollution emissions.1) However, H2
is presently produced by conversion of hydrocarbons or fossil fuels and is accompanied by enormous energy consumption and greenhouse gas emissions. To realize carbon neutral and sustainable circulation technology, carbon-free and green H2
production methods, such as water-splitting, are required. 2)

Results and discussion

This presentation describes organic π-conjugated polymers as a novel photoelectrocatalyst towards water-splitting.2-4) π-Conjugated polymers synthesized without residual metals were developed to function in "water", which defied common sense, leading to this novel catalytic ability. In detail, (1) we succeeded in synthesizing polythiophene, which is a type of π-conjugated polymer, in a film form without residual metal by our unique iodine-vapor-phase polymerization method (2) We found that this polythiophene film worked as a novel photoelectrocatalyst that absorbs visible-light and highly efficiently reduces water to generate H2
. (3) In addition, based on a rigid π-conjugated polymer structure, this polythiophene film catalyzed water-splitting/ H2
production with surprisingly high durability (more than 1 month without no degradation). The development of environmentally-friendly organic catalysts that do not use precious metals will lead to the production of truly green H2
.
We will also describe developments to other catalytic functions (O2
reduction/ H2O2
production etc.) of organic π-conjugated polymers.

References

1) Schlapbach, L. et al., Nature, 2001, 414, 353-358.
2) Oka, K. et al., Adv. Energy Mater., 2021, 11, 2003724.
3) Oka, K. et al., Energy Environ. Sci., 2018, 11, 1335-1342.
4) Oka, K. et al., Adv. Energy Mater. 2019, 9, 1803286.

Acknowledgment

This work was partially supported by Grants-in-Aids for Scientific Research (No. JP23K17945, JP23H03827, JP24K01552) from MEXT, Japan. K. Oka. also acknowledges the support from Shorai Foundation for Science and Technology, TEPCO Memorial Foundation, Amano Industry Technology Laboratory, Sugiyama Houkoukai, The Yamada Science Foundation, Kenjiro Takayanagi Foundation, Kansai Research Foundation for Technology Promotion, and JACI Prize for Encouraging Young Researcher.
(Invited) Organic Molecule and Polymer Nanoparticles in Biohybrid Photocatalysis
Authors: Tian Haining 
Published: December 2024

Organic molecule and polymer nanoparticles have found extensive application in photocatalysis for solar fuel production, owing to their excellent dispersion in water and customizable optical properties [1]. These nanoparticles, characterized by their small size and modifiable surface charge through different surfactants, present a unique opportunity for integration with bio-systems. While organic nanoparticles have been traditionally employed as fluorescent probes and phototherapy reagents [2], their exploration within bio-systems for solar fuel production remains underexplored. In our recent research, we present innovative approaches utilizing organic particle-based bio-hybrid systems for solar fuel production.
In one study, we successfully integrated polymer particles (Pdots) with FeFe hydrogenase, as evidenced by Cryo-EM and electrophoresis revealing a visually detectable interaction between Pdots and hydrogenase [3]. The Pdots-hydrogenase system demonstrated remarkable performance in light-driven hydrogen production.
In another investigation, we immobilized Pdots onto the membrane of Ralstonia eutropha H16 (RH16) bacteria and employed natural redox shuttle, utilizing natural red as a mediator between Pdots and RH16 bacteria to facilitate the transport of protons and electrons [4]. The resulting Pdots-RH16 bio-hybrid system exhibited a threefold increase in the yield of poly(3-hydroxybutyric acid) compared to the original RH16.
Furthermore, I will provide insights into the progress of our work within the EU Photo2Fuel project, specifically focusing on the development of biohybrid systems for CO2 fixation.

References

[1] Pavliuk M., et al., Chem. Soc. Rev., 2022, 51, 6909-6935

[2] Wu C., et al., Angew Chem Int Ed Engl. 2013, 52(11), 3086–3109

[3] Pavliuk M., et al., J. Am. Chem. Soc. 2022, 144, 30, 13600–13611

[4] Yu W., et al., ACS Appl. Mater. Interfaces, 2023, 15, 1, 2183–2191