bluuebunny/crossref_metadata_2025 huggingface dataset:
A Leading Role of I'MSEP for Carbon Negative Technologies by Molten Salt Electrochemical Research
Authors: Terada Seiji , Hyodo Yoshikazu , Nakanishi Ryo , Koyama Akira , Sah Santosh Prasad , Nomura Yohei , Kunihiro Takao
Published: December 2024

I’MSEP Co., Ltd is a brainchild of the late Prof. Yasuhiko Ito who passed away last year at the age of 82. Prof. Ito was a fellow member of The Electrochemical Society. Prof. Ito focused on working and developing electrochemical processes in molten salts throughout his career at Kyoto University and Doshisha University (Japan). Fig. 1 illustrates the themes of research on which I’MSEP is now working. In this meeting, the authors will briefly talk on formation of carbon particles by plasma-induced discharge electrolysis (PiDE) and the conventional electrolysis, and also reckon up their merit. The produced carbon materials can be used for next-generation secondary batteries and fuel cells.

In PiDE, carbon submicron-particles are produced under plasma discharge in a molten salt bath containing carbonate ions. The plasma is generated at the W (tungsten) cathode placed just above the molten salt while a specific anode was dipping into the melt. The molten salt was the eutectic mixture of 58.5LiCl–41.5KCl (mol%) (m. p. 352°C), and was used at 450°C under argon atmosphere. The molten salt contained 2 mol% K2CO3 dissolved within it, acting as the carbon source. Extremely fine carbon particles (size <1 μm) can be produced with PiDE.

Carbon particles produced with PiDE showed high electrochemical performance. Downsizing carbon particles beyond 1 μm is difficult with the conventional electrolysis. On the other hand, the conventional electrolysis can produce carbon of different morphology like granular, filamentous, flaky, columnar, membrane-like (both dense and porous). Finer carbon particles were successfully formed in Li-free molten salt, and work is going in this direction.

Figure 1
Acetylene Synthesis from CO2 and H2O Via Electrochemical Formation of Metal Carbides in High-Temperature Chloride Melt
Authors: Suzuki Yuta , Tanaka Seiya , Watanabe Takashi , Tsuchii Takane , Isogai Tomohiro , Yamauchi Akiyoshi , Kishikawa Yosuke , Goto Takuya
Published: December 2024

Research on CO2 conversion into valuable materials has attracted much attention, aiming to realize carbon neutrality and carbon-negative emission technology. It has been reported that the unique physicochemical properties of high-temperature molten salt, such as high conductivity and wide electrochemical window, make it possible to obtain solid carbon directly from CO2 and metal carbides.

In this study, we focused on the electrochemical formation of CaC2 from CO2 in high-temperature chloride melt. CaC2 is the raw material for acetylene, the starting material for various chemical products. This study demonstrated the selective formation of CaC2 from CO2 by an electrochemical process in NaCl-KCl-CaCl2-CaO melt at 823 K to produce C2H2 with high current efficiency. When the inert material for oxygen evolution in the high-temperature melts was used as the anode, the formation of acetylene and oxygen from carbon dioxide and water can be realized as the total reaction.

2CO2 + H2O → C2H2 + 5/2O2

On the metal cathode, the CaC2 was formed through two reactions: the carbon electrodeposition from CO2-derived CO3
2− (Step 1) and the electrochemical reduction of Ca(II) ion on the carbon (Step 2). These two reactions could be controlled by conducting potentiostatic electrolysis under CO2 and Ar atmospheres, resulting in acetylene synthesis with a maximum current efficiency of 92%. The electrolysis on carbon electrodes revealed that the higher the crystallinity of carbon, the more selectively CaC2 was formed. The CaC2 formation was induced by the reduction of Ca(II) ions on the basal plane of the graphite layer rather than the edge plane. The unique interfacial phenomenon between high-temperature melt and a carbon electrode surface will contribute to realizing a highly efficient CO2 conversion process to acetylene. It was found that the electrochemical formation of CaC2 tends to proceed at the basal plane of the graphite layer. This reaction mechanism is entirely different from the interlayer reactions that tend to occur in LIBs and is unique to this electrolytic system at the carbon/molten salt interface. The obtained data will provide a highly efficient process for CO2 resource conversion and physicochemical insights into new carbon surface reactions.
Probing Decomposition of Iron Disulfide in Molten Salt Eutectics
Authors: Schorr Noah B. , Macchi Sam , Johnson Linda , Montoya Bertha , Harrington Alan , Taphouse John
Published: December 2024

Iron disulfide is common active material for primary molten salt battery cathodes. The choice of operational temperature of molten salt FeS2 batteries is an interplay between maintaining temperature to melt the eutectic, increase cell voltage, and operate within a stable region for the active materials. While FeS2 has been used for decades for this application, understanding the controlling factors of decomposition is still required to improve battery performance. To understand thermal decomposition of FeS2, often the powder is looked at using thermal gravimetric analysis (TGA) and differential scanning colorimetry. However, the thermal properties of the powder in an inert atmosphere, like those often used in a TGA, are not representative of the properties seen in molten eutectic. In this work we look at a variety of FeS2 powders from different vendors that have a distribution of particle sizes (D50 20-150 µm) and surface areas (1-10 m2/g). Using TGA, the onset temperature for thermal decomposing under an argon atmosphere and in a molten LiCl-KCl eutectic is determined. High resolution modulated TGA was implemented to quantify the energy of activation of decomposition under both conditions. This technique enables calculation of an Ea at every temperature value. When in the eutectic the FeS2 decomposed at higher temperature compared to in Ar, increasing from ~500°C to ~550°C and was found to have a higher energy of activation for the decomposition process. This was found to be true regardless of the size of the FeS2 particles. TGA with tandem mass spectrometer was then used to investigate differences in the mechanism of the decomposition of the two conditions. Using the results of the instrumental analysis we compare the quantitative properties of FeS2 decomposition to the performance of molten salt batteries at different temperature. Specifically, the electrochemical performance of FeS2 was tested by single cells (FeS2||LiCl-KCl||LiSi) at temperatures between 450-570°C. The differences in iron sulfide decomposition in a eutectic versus when in a full electrochemical cell will be discussed.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
Ternary Ionic Liquid Analogues for Ambient and Low-Temperature Rechargeable Aluminum Batteries
Authors: Wang Jonah , Schoetz Theresa , Gordon Leo W. , Biddinger Elizabeth J. , Messinger Robert J.
Published: December 2024

Many issues surround lithium, such as scarcity, safety, and ethical extraction. One promising alternative to lithium-ion batteries are aluminum batteries, which offer the earth abundance, inherent safety, high theoretical capacity, and low cost of aluminum metal. Additionally, batteries for transportation, space, or defense applications may often need to operate at low temperatures, where electrolytes exhibit lower ionic conductivity and are prone to freezing. The state-of-the-art electrolytes for aluminum batteries, Lewis acidic AlCl3 (aluminum chloride)-[EMIm]Cl (1-ethyl-3-methyl-imidazolium chloride) ionic liquids (ILs), are not cost effective and exhibit low ionic mobilities and conductivities below 0 oC. Their electrochemical and thermophysical properties can be tuned by adding a third species, such as urea. The AlCl3-urea ionic liquid analogue has also been investigated as a lower cost alternative. However, little research has been done on ternary mixtures of AlCl3-urea-[EMIm]Cl, including investigations of their physical properties and ability to reversibly electrodeposit Al metal from ambient to low temperatures.

In this work, AlCl3-urea-[EMIm]Cl mixtures with molar ratios of 1.3:X:(1-X) molar ratios were synthesized, where X = 0, 0.125, 0.25, 0.5, 0.75, and 1. Physical and electrochemical properties were characterized from ambient to low temperatures (down to -70 oC) with spectroscopic, thermoanalytical, and electrochemical measurements. Differential scanning calorimetry (DSC) was utilized to observe the thermal behavior of the electrolytes and determine their liquid-phase temperature windows. Quantitative liquid-state 27Al and 1H single-pulse nuclear magnetic resonance (NMR) experiments revealed how the types and populations of the polyatomic aluminum complexes changed based on urea concentration, as well as understand how the local environments of the EMIm+ cations and urea change across different compositions. The Al electrodeposition capability of the electrolyte mixtures were tested from 25 to -70 oC, both galvanostatically (two-electrode cells) and potentiodynamically (three-electrode cells). Subsequently, the most promising electrolyte compositions were tested in Al-graphite batteries to determine their technological feasibility and electrochemical properties, particularly at lower temperatures. The results indicate that AlCl3-urea-[EMIm]Cl in a 1.3:0.25:0.75 molar ratio can be used to enhance the electrochemical performance, reduce the cost, and expand the operating temperature window of rechargeable aluminum batteries compared to the AlCl3-[EMIm]Cl standard.
Development of Dual-Carbon Batteries with Amide-Based Ionic Liquid Electrolytes
Authors: Yamamoto Takayuki , Oe Riku , Uehara Keigo , Ishio Yoshifumi , Yadav Alisha , Nohira Toshiyuki
Published: December 2024

Increasing demands for large-scale energy storage systems have driven us to the development of various next-generation batteries as alternatives of lithium-ion batteries (LIBs). Current LIBs potentially possess a major concern about the supply instability of scarce cobalt resources used in positive electrode materials. Dual-carbon batteries (DCBs) are considered as one of the promising solutions because DCBs are composed of carbon-based materials for both positive and negative electrodes, and thus they are free from the utilization of rare metals. We have focused on ionic liquids (ILs) as electrolytes for DCBs [1,2]. In contrast to so-called rocking-chair-type batteries like practical LIBs, the charge carrier ions are reserved in the electrolytes at the initial (discharged) state of DCBs, which is expressed as reserve-type batteries and requires large charge carrier densities in the electrolytes. Typical ILs are composed of only cations and anions without neutral solvents [3], indicating the eligibility of DCB electrolytes.

We recently conducted a systematic study on the charge–discharge behavior of graphite positive electrode in FSA- and FTA-based ILs (FSA = bis(fluorosulfonyl)amide, FTA = (trifluoromethylsulfonyl)(fluorosulfonyl)amide) [1]. Although the graphite positive electrodes showed higher reversible capacities in FTA-based ILs compared to FSA counterparts, Na[FSA]-based IL specifically gave moderate discharge capacities of approximately 80 mAh g−1. Furthermore, we selected K[FTA]-based IL as a promising electrolyte and demonstrated the graphite/graphite full-cell operation [2]. This IL-based DCBs exhibited reasonably high performance for 300 cycles in terms of capacity retention ratio and coulombic efficiency.

In the present study, we will comprehensively discuss the charge–discharge behavior of graphite positive electrode in amide-based IL electrolytes including further investigation of the specific phenomena in the Na[FSA]-based IL.

Acknowledgments

This study was partly supported by JSPS KAKENHI grants (JP21K14718 and JP24K01602) and a research grant from the Murata Science and Education Foundation.

References

[1] T. Nikaido, A. Yadav, T. Yamamoto, and T. Nohira, J. Electrochem. Soc., 170, 020526 (2023).

[2] A. Yadav, H. Kobayashi, T. Nikaido, T. Yamamoto, and T. Nohira, J. Power Sources, 585, 233628 (2023).

[3] T. Yamamoto and T. Nohira, Chem. Rec., 23, e202300169 (2023).
Redox Reaction of Some Nitroxyl Radicals in 1-Butyl-1-Methylpyrrolidinium Bis(fluorosulfonyl)amide in the Presence and Absence of Lithium Ion
Authors: Katayama Yasushi , Kato Shodai , Serizawa Nobuyuki
Published: December 2024

Ionic liquids composed of bis(fluorosulfonyl)amide (FSA–) have been investigated as the promising electrolytes for rechargeable lithium batteries due to their high conductivity and low viscosity dependence on the Li salt concentration. Despite many reports on FSA–-based ionic liquids as the electrolytes for rechargeable lithium and sodium batteries, a few studies have been reported on the electrode reactions of redox species. The redox reactions of Ag+/Ag and ferrocenium (Fc+)/ferrocene (Fc) were investigated in BMPFSA (BMP+ = 1-butyl-1-methylpyrrolidinium)[1]. It was reported that the donor ability of FSA– was found to be lower than that of bis(trifluoromethylsulfonyl)amide (TFSA–) from the potential difference between Ag+/Ag and Fc+/Fc. 2,2,6,6,-Tetramethylpiperidine-1-oxyl (TEMPO) is one of the typical niroxyl radicals with redox activity. In the present study, the redox reactions of TEMPO and 4-oxo-TEMPO were investigated in BMPFSA in the presence and absence of lithium ion.

The redox reactions of TEMPO+/TEMPO and 4-oxo-TEMPO+/4-oxo-TEMPO were observed on a Pt electrode in BMPFSA by cyclic voltammetry. The formal potential of TEMPO+/TEMPO was lower than that of 4-oxo-TEMPO+/4-oxo-TEMPO. The formal potential of TEMPO+/TEMPO in the presence of Li+ was higher than that in the absence of Li+, suggesting that the interaction between TEMPO and Li+ affected the thermodynamic properties of the redox species. The diffusion coefficients and the standard rate constants were evaluated by chronoamperometry and electrochemical impedance spectroscopy, respectively. The diffusion coefficient and the standard rate constant were suggested to be controlled not only by the viscosity but also by the interaction between the nitroxyl radicals and Li+.

Reference

[1] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 046504 (2023).
Generation of Non-Cellulosic Biopolymer Xerogels Using Ionic Liquid Based Natural Fiber Welding
Authors: Trulove Paul C. , Larm Nathaniel E. , Stachurski Christopher D. , Cho Whirang , Lentz Louis R. , Ahearn Sophia , Durkin David P.
Published: December 2024

Natural Fiber Welding (NFW) is a process that can be used for the non-derivative dissolution, restructuring, and recycling of biopolymer fibers. NFW leverages the unique solvating power of ionic liquids to mobilize and reconfigure the outermost polymer strands of adjacent fibers, “welding” them into a new singular matrix while maintaining the majority of their native structure. Recently, our group developed a modification to the fiber welding process that drastically impacts the surface area of the welded matrix. Ionic liquid removal using a polar rinse solvent (i.e., water) and then solvent exchange to a final nonpolar solvent (i.e., cyclohexane) produces nanoporous all-cellulose xerogels with up to a 20,000-fold increase in measured surface area compared to cellulose substrates treated with the standard NFW process. The current work looks at the potential of NFW to generate high surface area xerogels from non-cellulosic polysaccharides and polypeptides. We will present our evaluation of NFW procedure modifications to account for specific differences in the chemical nature of the biopolymer substrate (e.g., polysaccharide –OH and –NH2 versus polypeptide –OH, –NH2, –SH, –COOH, and imidazole groups), and we will present our characterization of generated materials using inverse gas chromatography, BET surface analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The impact of ionic liquid and solvent processing on non-cellulosic biopolymer material surface properties and xerogel porosity will be discussed.
Radiation-Driven Reactivity of Metal Ions in Molten Salts
Authors: Wishart James F. , Iwamatsu Kazuhiro , Layne Bobby , Kim Ellie , Halstenberg Phillip , Dai Sheng , LaVerne Jay A. , Holmbeck Gregory P. , Conrad Jacy , Gakhar Ruchi , Woods Michael E.
Published: December 2024

Molten salts are proposed as liquid fuels or coolants in a new fleet of molten salt nuclear reactors that would have operational and safety advantages over present reactor systems. Under those conditions, the salt will be exposed to high radiation levels, and understanding the chemical effects of radiolysis on the molten salt fuel or coolant is essential to reliable, efficient and sustainable reactor operation. Building this understanding begins with identifying primary salt radiolysis products (solvated electrons (esolv
–) and Cl2
•–) and characterizing their reactivities, for which we conduct high-temperature pulse radiolysis transient absorption spectroscopy at the BNL Laser-Electron Accelerator Facility. Here we report on the reaction kinetics of reactions of metal ions with esolv
– and Cl2
•– in different molten salt compositions. Salt mixtures containing mono- and divalent cations are particularly interesting because of their tunable Lewis acidity-basicity that can be used to control the solubility and redox poise of dissolved metal ions in the reactor. Previously we showed how varying the MgCl2:KCl mixing ratio alters the absorption spectra of radiolytically-produced excess electrons, with increasing blue shifts related to the likely number of Mg2+ ions adjacent to the cavity electron. The strong blue shifts indicate significant changes in the electron’s energetics and reactivity that we now have probed by measuring reaction kinetics with metal ion electron acceptors. We observed that reaction rates of the solvated electron depend strongly on the composition of the salt. Reactivity trends among first-row transition metals in eutectic LiCl-KCl will be discussed. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.
Molecular Dynamics Simulation Reveals the Transport Mechanism of Molten Alkali Metal Amides
Authors: Kiyobayashi Tetsu , Kubota Keigo , Kiyohara Kenji
Published: December 2024

The ionic conductivity of molten LiFSA, LiFTA and LiTFSA is peculiarly lower than that of other alkali metal counterparts, where FSA = bis(fluorosulfonyl)amide, FTA = fluorosulfonyl(trifluoromethylsulfonyl)-amide, TFSA = bis(trifluoromethylsulfonyl)amide. Another peculiarity of these lithium amides is that their ionic conductivity, σ, exceeds the Nernst-Einstein conductivity, σNE, a hypothetical conductivity that would be observed if ions were moving without correlating each other. Because the correlations between ions tend to impede their movement, σ < σNE for many cases including not only molten salts, ionic liquids but also electrolyte solutions. The present molecular dynamics (MD) simulation attempts to solve these mysteries in the transport mechanism of AFSA, AFTA and ATFSA (A = Li, Na, K, Rb, Cs).

We adopted the Lennard-Jones potential and the Yukawa potential (∝ exp(-κr)/r) for the intermolecular interactions of MD. The screening parameter, κ, of the Yukawa potential implicitly introduces the effect of induced polarization into the electrostatic interaction. We treated κ as an empirical parameter and determined it so as the simulated σ to reproduce the experimental results. The ionic conductivity σ was calculated by the time integral of the microscopic current correlations in the framework of the Green-Kubo formulation. The calculated σ can be divided into five terms, where the subscripts + and - stand for the cation and the anion, respectively:

σ = σ+ + σ++ + σ- + σ-- + 2σ+-

where σ±, σ±± and 2σ+- respectively represent the contribution to σ from the auto-correlation of each ions (σNE = σ+ + σ-), the cross-correlation between ions of the identical sign, and the cross-correlation between ions of the opposite sign.

The simulation results suggest that, for K, Rb and Cs-salts, σ±± < 0, which is understandable because the ions of the identical sign repel each other to attenuate the microscopic current and hence their correlations negatively contribute to σ. However, for Li-salts, σ-- < 0, but σ++ > 0, which is the proximate cause of bringing σ > σNE. The simulation also suggests that σ- + σ-- ～ 0 for Li-salts; i.e., anions little contribute to the total conductivity as if these salts were solid electrolytes of Li. In the presentation, we will dig deeper into the issues by hypothetical questions, such as "What if Li were bigger?", "What if Li were lighter/heavier?", etc.

Figure 1
Experimental and Theoretical Studies of the Solid-State Performance Ofelectrodeposited Yb2O3/As2Se3 Nanocomposite Films
Authors: Alshoaibi Adil
Published: December 2024

The influence of the rare-earth oxide (Yb2O3) on arsenic selenide (AseSe) host is currently investigated

and documented in this study. Nanocomposite films were grown using the electrodeposition (ED)

technique with the addition of 1 e 4 mol% Yb2O3. The film’s optical structural, optical, morphological,

and electronic features were studied. The host matrix presents the monoclinic structure whereas the

composite films present two phases ecubic and orthorhombic crystal structure. Crystallites within nano

sizes (36.2 nm) were recorded for the pristine film while the composite films showed sizes ranging from

37.2 to 48.1 nm. Moreover, the Raman spectra revealed low energy Raman phonons characteristic of Se8

rings, As4Se4 cages, AseSe hetero-polar bonds whose cleavage was due to the diffusion of the Yb ions

into the host matrix as shown by the Raman shift. More so, the refractive index peaked at n ¼ 2.66 in the

l interval of 350e600 nm, while the SEM images showed nano-balls and nanoclusters which are fairly

homogeneous. PL studies exhibited multimode emission bands spanning the UVeViseNIR regions. Firstprinciples

calculations were employed to investigate the structural properties and electronic structure of

the pristine (AseSe) film, as well as Yb contribution. It was found that Yb addition leads to reduce the

bandgap energy and consequently the lone pair p-states of Se contribute nearby to Fermi energy level.

Hence, the experimental and theoretical results of films afford potential applications in phase-change

memory (PCM) and downconverting solar cell window layer.
(Invited) All-Solid-State Photoelectric Conversion Cells Employing the Combination of Metal Nanoparticle and p-Type Semiconductors for Plasmon-Induced Charge Separation
Authors: Takahashi Yukina
Published: December 2024

Metal nanoparticles, such as gold and silver nanoparticles, can localize light energy to the nanospace near the particle surface by localized surface plasmon resonance (LSPR) under light irradiation at resonant wavelengths. In addition, by controlling parameters, such as shape and size of the metallic nanoparticles, it is possible to control the light absorption properties at any wavelength in the range from visible to near-infrared. Therefore, LSPR of metal nanoparticles is attracting attention as a technology for effective use of sunlight. When metal nanoparticles combined with semiconductors are irradiated with light at resonant wavelengths, charge is transferred from the metal nanoparticles to the semiconductors. This is called plasmon-induced charge separation (PICS) (Fig. 1(a)), and is expected to be applied to photoelectric conversion, photocatalysis, and sensing using light in the visible to near-infrared region.

Conventionally, the semiconductors to be combined are mainly n-type such as TiO2. In conventional systems, a positive charge is generated on the metal nanoparticle side, causing oxidative dissolution into the electrolyte, so the only practical options for metal nanoparticles were Au (or Ag with improved stability). In the case of all-solid-state systems that do not use an electrolyte, the counter electrode must be made of a material with a low work function, such as Al or In, which has an ohmic contact at the interface with the n-type semiconductor, resulting in air oxidation and low long-term device stability (Fig. 1(c)) [1].

In this study, we fabricated all-solid-state cells using p-type semiconductors as the semiconductor combined with metal nanoparticles (ITO/metal nanoparticles/p-type semiconductor/Au) (Fig. 1(d)). In this system, it was found that Ag and Cu can also be used as metal species because negative charges are generated on the metal nanoparticle side (Fig. 1(b)). In addition, Au, which makes ohmic contact with p-type semiconductors, could be used as the counter electrode, which dramatically improves the long-term stability of the device in air [2].

The all-solid-state photovoltaic cells composed of p-type semiconductors and metal nanoparticles realized in this study is expected to be applied as a cost-effective solar cell with a simple structure and high stability, as well as in various other applications, such as sensing and photocatalytic systems.

[1] Y. Takahashi, T. Tatsuma, Appl. Phys. Lett., 99, 182110(1 – 3) (2011).

[2] Y. Takahashi, Y. Yamadori, T. Murayama, S. Shingo, S. Yamada, in preparation.

Figure 1
(Invited) Metal and Compound Nanostructures Fabricated Via Photoelectrochemical Reactions
Authors: Nishi Hiroyasu
Published: December 2024

Metal and compound nanoparticles or nanostructures have unique properties that are different from bulk materials. For instance, metal nanoparticles exhibit light absorption and scattering due to localized surface plasmon resonance (LSPR) while compound nanoparticles such as CdS emit photoluminescence because of quantum size effects. The optical and photoelectrochemical properties of nanomaterials are significantly dependent on their size, shape, orientation, periodicity, and combination with other materials. Therefore, nanofabrication methods to control these factors are of critical importance for photovoltaic, photocatalytic, and other applications.

We have successfully demonstrated photoelectrochemical techniques to fabricate different nanostructures composed of metal and/or metal oxide. Au-PbO2[1,2] and Au-Ag[3] hetero-nanostructures were fabricated via plasmon-induced charge separation (PICS)[4,5] in the presence of Pb2+ and Ag+ ions, respectively. Site-selective oxidative or reductive deposition took place at the resonance sites under excitation of LSPR of Au nanoparticles, that are in contact with a semiconductor such as TiO2 or a potential-controlled electrode. The reaction site can be controlled only by changing the irradiation wavelength. PbO2 deposited on the Au nanoparticles was galvanically replaced with MnO2 as a cocatalyst of photocatalytic reaction based on PICS[6]. Recently, we fabricated PbO2 periodic nanostructures by irradiating incoherent linearly polarized visible light to a potential-controlled bare indium-tin oxide electrode in the presence of Pb2+ ions[7] (see the image below). These photoelectrochemical approaches allow us to fabricate a variety of nanostructures with sizes beyond or comparable to the diffraction limit of light.

References

[1] H. Nishi, M. Sakamoto, T. Tatsuma, Chem. Commun.
2018, 54, 11741.

[2] H. Nishi, T. Tatsuma, Nanoscale
2019, 11, 19455.

[3] H. Nishi, Y. Zuo, Y. Kuroiwa, T. Tatsuma, in preparation.

[4] Y. Tian, T. Tatsuma, J. Am. Chem. Soc.
2005, 127, 7632.

[5] T. Tatsuma, H. Nishi, T. Ishida, Chem. Sci.
2017, 8, 3325.

[6] K. Kim, H. Nishi, T. Tatsuma, J. Chem. Phys.
2022, 157, 111101.

[7] H. Nishi, H. Tojo, A. Kawai, T. Tatsuma, ACS Appl. Nano Mater.
2024, 7, 5426.

Figure 1
Photo-Electro-Upcycling of Biomass via Dye-Sensitized Photoanode with Passivation Effect
Authors: Lee Jeong Kyeong , Kwon Tae_Hyuk
Published: December 2024

Solar valuable chemical conversion is being actively studied for a sustainable environment. Organic dyesensitized semiconductor systems are suitable due to their easy band gap tuning, broad absorption spectrum, facile fabrication, and relatively low priced compared to metal complexes to convert light to valuable substances effectively and stably. However, charge transfer from biomass to oxidized organic dye is relatively slow in typical dye-sensitized photoelectrochemical cells, resulting in remarkably low

current density, unlike photovoltaics. Hence, the holes can be extracted from organic dye-sensitized photovoltaic system with passivation effect enhancing its efficiency and they can directly oxidize biomass. Organic dyes are researched to generate high current and voltage related to conversion yield and selectivity, so we designed IDT-1−4 organic dyes. Significantly, the methyl functional group is introduced to the acceptor unit to prevent loss of the photovoltage through slow recombination from TiO2 to oxidized organic dyes. This study shows that biomass can be oxidized and degraded with low applied bias and relatively short time.
Electrochemical Synthesis and Optimization of CdSexTe1-X Thin-Films for Enhanced Solar Cell Performance
Authors: Damaghi Amirreza , Ali Karami Somayeh , Adesanoye Samuel , Vijay Shiljashree , Cheng Wei , Jawahar Hussaini Syed Mubeen
Published: December 2024

The considerably wide light absorption spectrum and excellent chemical stability of CdSexTe1-x alloyed thin films show its significant applicability in solar cell thin film technology. In this study, a novel, economical electrodeposition technique was utilized to synthesize the CdSexTe1-x thin films, offering a simpler setup and reduced energy consumption compared to other methods of solar cell fabrication used in industrial scale. The performance of CdSexTe1-x thin film was examined with respect to several parameters, such as electrolyte composition, electrodeposition potential, treatment solution, and annealing temperature. XRD, SEM, and EDS were employed to investigate the fabricated CdSexTe1-x thin film's crystallinity, morphology, and elemental compositions. The synthesized CdSexTe1-x thin film demonstrated promising fill factor, short circuit photocurrent density (Jsc), and open-circuit voltage (Voc). The results reveal that the synthesized CdSexTe1-x thin film exhibited enhanced physical characteristics and photoelectrochemical solar cells performances as remarkable light harvesting absorber layers.
Synthesis of Near-IR-Responsive Ag-Au-Te Quantum Dots with a Heating-up Method
Authors: Kikkawa Atsushi , Miyamae Chie , Akiyoshi Kazutaka , Kameyama Tatsuya , Sato Hiroki , Ohshima Yusuke , Torimoto Tsukasa
Published: December 2024

Quantum dots (QDs) exhibit optoelectronic properties different from bulk materials due to the quantum size effect. Recently, near-IR-responsive QDs have attracted significant attention for developing highly efficient solar energy conversion systems and novel luminescent probes for in vivo bio-imaging. We previously reported that I-III-VI-based QDs of less toxicity, such as Ag(In,Ga)Se2, exhibited a sharp bandedge PL peak, the wavelength of which was controllable with their composition.(1) Here, we report the solution-phase synthesis of Ag-Au-Te QDs with low toxicity and evaluate their photoresponse in near-IR wavelength region.

Ag-Au-Te QDs were prepared by reacting corresponding metal complexes and Te compounds in a hot organic solvent. After cooling to room temperature with continuous stirring, the Ag-Au-Te QDs were isolated from the solution by adding ethanol, followed by dispersing in chloroform. The composition of the resulting QDs varied by changing the Ag/Au ratio in the precursors. TEM observation revealed that obtained Ag-Au-Te QDs with the average size of ca. 4 nm. With measurements of XRD patterns and EDX analysis, it was found that the obtained particles were Ag2Te QDs doped with Au. Absorption spectra demonstrated that thus-obtained Ag-Au-Te QDs absorbed light from the visible to the near-infrared wavelength ranges, with an absorption onset wavelength of approximately 1600 nm. Ag-Au-Te QDs exhibited a broad PL peak due to the defect-site emission with a PL quantum yield (PLQY) of 0.8%, which was slightly higher than that of Ag2Te QDs, 0.2%. In conclusion, we successfully synthesized Ag-Au-Te QDs showing near-IR photoresponse, holding promise for applications in photovoltaics and bio-imaging.

Reference

(1) T. Kameyama, et al., ACS Appl.
Nano Master., 2020, 3, 3275.
(Invited) Evaluation of Oxygen Evolution Reaction Electrodes through Machine-Learning Analysis and in-Situ Electrochemical Spectroscopy
Authors: Fukushima Tomohiro , Itatani Masaki , Murakoshi Kei
Published: December 2024

To enhance the catalysis of the oxygen evolution reaction (OER) at water electrolysis electrodes, it is imperative to eliminate the energy-consuming processes involved in multiple electron and proton transfer reactions. We propose employing a combination of machine-learning analysis of electrochemical activity and in-situ electrochemical Raman observation for the OER electrodes. The OER behavior can be categorized based on the contributions of Ni-OH and Ni-OOH, which serve as key OER intermediates. This information is utilized to elucidate the OER behavior through energetic and intermediate analyses. The presented study provides the direction for designing active OER catalysis in the future.
(Invited) Light-Guided Electrodeposition for Functional Integration of Catalyst Pattern on Semiconductor for Efficient Oxygen Evolution Reaction
Authors: Lee Suyeon , Im Hanseo , Lee Nayeon , Lim Sung Yul
Published: December 2024

Photoelectrochemical cells (PECs) for water splitting typically rely on catalysts deposited on the semiconductor due to its lack of intrinsic electrocatalytic activity. However, the placement of catalysts within the light path between the source and semiconductor in artificial leaf-based architectures can hinder the semiconductor's light absorption, diminishing photoelectrochemical activity, especially at high catalyst loading. To address this challenge, we propose a strategy involving the controlled formation of patterned catalysts on the semiconductor surface. This approach, utilizing light-guided electrodeposition facilitated by a digital micromirror device (DMD), enables the direct, localized deposition of transition metal-based catalysts. The resulting patterned catalysts correspond to the light pattern, allowing for optimized photoelectrochemical performance. We demonstrate the efficacy of this strategy on a hematite (α-Fe2O3)-based photoanode, achieving enhanced performance with grid-patterned CoPi catalysts. This approach not only facilitates high catalyst loading but also ensures sufficient light penetration through the exposed intrinsic surface of α-Fe2O3. Our findings suggest that this technique holds promise for advancing the commercialization of PECs, particularly for self-biased water splitting devices aimed at green H2 production.
Modeling the Effects of Local Species Concentrations on the Selectivity of a Modified Cobalt Phthalocyanine Catalyst for CO2 Reduction to Produce Methanol
Authors: Silcox Rachel , Yao Libo , Rivera Cruz Kevin Enrique , McCrory Charles , Singh Nirala , Bala Chandran Rohini
Published: December 2024

Methanol is a desirable end-product from CO2 reduction as it serves as a drop-in renewable fuel for the current fuel and transportation economy. Cobalt Phthalocyanine (CoPc) is an effective electrocatalyst to convert CO2 into methanol by preventing C-C coupling. In prior work with gas-fed CO2 electrolyzers, it has been shown that methanol production is suppressed when the relative concentration of CO2 to CO increases, as reaction sites for CO to methanol are blocked [1]. Therefore, having knowledge of the local concentrations of CO2 and CO can be significant to improve understanding and interpretation of experimental data. To probe these effects of mass-transfer in a gas-fed CO2 flow cell, we develop a three-dimensional computational model of the gas flow adjacent to the gas diffusion electrode. Different flow rates (1-30 ml/min) and partial pressure of the feed CO2 gas (0.02 - 1 atm) are modeled concurrently with inputs of experimentally measured partial current densities for methanol, carbon monoxide, and hydrogen formation. Model predictions determine space-time variations in the concentrations of all relevant reactant and product species. These are correlated with the relative concentrations of CO2 and CO on the measured reaction rates and selectivity. Results highlight that methanol production only occurs at sufficiently low mass flow rates or partial pressures of CO2 reactant gas, leading to low relative CO2 to CO concentrations. The value of the companion model developed is that it identifies the maximum value of the relative CO2 to CO concentration in the reactor that still yields methanol. Future predictive modeling studies can harness these local CO2:CO concentrations to relate to methanol productivity. Additionally, the modeling framework developed is applicable to probe and identify CO2 electrolyzer design/operating conditions that can enhance the relative concentration of CO as compared to CO2.

[1] Yao et al. (2024) Electrochemical CO2 Reduction to Methanol by Cobalt Phthalocyanine: Quantifying CO2 and CO Binding Strengths and Their Influence on Methanol Production. ACS Catalysis DOI:10.1021/acscatal.3c04957
In Situ Stability Analysis of Oxygen Evolution Reaction Via Mass Spectrometry
Authors: Chung Dong Young
Published: December 2024

There is a growing evidence suggesting that design principles in various fields, particularly in electrochemistry, should encompass considerations of both activity and stability. Achieving high activity alongside stability is important, yet many studies still treat these aspects as separate objectives. To overcome this limitation, establishing functional links between activity and stability based on underlying reaction mechanisms is essential. Through in situ (operando) analysis, this study aims to elucidate the interplay between activity and stability, particularly in the context of the oxygen evolution reaction, utilizing real-time mass spectrometry. By conducting comprehensive investigations, we can unveil the intricate relationships between stability and activity in electrochemical environments, thus paving the way for the design of new materials that exhibit both heightened activity and robust stability.
(Invited) Coherent X-ray Studies of Electrode Nanoparticles and Surfaces
Authors: You Hoydoo , Kawaguchi Tomoya , Komanicky Vladimir
Published: December 2024

Coherent X-rays provide a unique structural and dynamical viewpoint of electrode surfaces and nanoparticles. Using the coherent X-ray techniques, we have been studying several electrochemical phenomena such as electrochemical dissolution reactions of silver surfaces and nanoparticles, oxygen reduction/evolution reactions of platinum and platinum alloy nanoparticles, and the surface reconstruction dynamics of gold surfaces and nanoparticles. The coherent X-ray techniques are typically developed for real-space images and real-time dynamics. For imaging techniques, X-ray imaging such as Bragg Coherent Diffraction Imaging (BCDI) is used to image nanoparticles, and X-ray Ptychography is used to image electrode surfaces, and X-ray photon correlation spectroscopy (XPCS) is used to monitor the electrode surface dynamics.

In this talk, we will present a broad overview of the examples based on our previous studies and provide each example with an emphasis on the uniqueness of the coherent X-ray techniques and the structural and dynamical aspects of the electrodes, unavailable in traditional X-ray techniques. We will also provide a perspective of the coherent X-ray techniques using the more powerful and brilliant coherent X-rays becoming available in the newest generation X-ray photon sources such as upgraded Advanced Photon Source (APS-U).
(Invited) Direct Electrochemical Reduction of Carbonate to Formate
Authors: Yeo Boon Siang Jason
Published: December 2024

We shall show in this presentation that carbonates (CO3
2-), typically regarded as being electrochemically-inert, can be directly electroreduced to formate. Through a combination of in situ Raman spectroscopy, HPLC, NMR spectroscopy, 13C and deuterium isotope-labelling, and DFT simulations, our study reveals that carbonate intermediates are adsorbed onto a copper electrode during CO2RR in KHCO3 electrolyte across potentials ranging from 0.2 to –1.0 V vs. RHE. These intermediates exhibit the capability to be reduced to formate at –0.4 V vs. RHE and at more negative potentials. Our observation is corroborated by the detection of formate resulting from the direct reduction of Cu2(CO3)(OH)2. We further conducted pulse electrolysis on a copper electrode immersed in N2-purged K2CO3 electrolyte, and show that the carbonate anions can first adsorb at –0.05 V vs. RHE and then be directly reduced to formate at –0.5 V vs. RHE with a Faradaic efficiency of 0.61 %. We elucidate the catalytically-active sites and propose a mechanism for the pulse-enabled reduction of carbonate to formate. These findings shed light on a direct route for the reduction of carbonates to a valuable product like formate and offer a potential approach for mitigating carbonate formation during CO2RR.
Selective Electrochemical CO2 Reduction Reaction By Tuning Electrolyte Conditions
Authors: Hwang Yun Jeong
Published: December 2024

Electrochemical CO2 reduction (CO2R) can be integrated with renewable energy sources and water can be utilized as a direct proton source which is promising to provide a sustainable net-zero carbon cycle. However, using water as the proton source causes undesired competitive hydrogen evolution reaction (HER), and thus it is crucial to control selectivity for CO2R. Various metal-based electrocatalysts have been investigated to convert CO2 to CO, formate, ethylene, ethanol, or other C2+ chemicals. Recent efforts to understand the electrocatalytic activity have found that the cations in the electrolyte play an important role in modulating the activity even for a given electrocatalyst. In addition, the influences of the cations vary depending on the types of reactions and catalysts when the cations interact with the intermediate species, and CO2R is a sensitive reaction to the presence of the cations. Therefore, the catalyst and electrolyte interface must be carefully investigated. The relationship between the product distribution of CO2R and its intermediate species can be monitored by operando spectroscopy studies that have attracted attention. We demonstrate that *CO, one of the crucial intermediates, can be observed by Raman or Infrared spectroscopy, and their vibrational wavenumbers depend on the electrolyte condition. Meanwhile, we also investigate selectivity for electrochemical CO2 conversion to CO production between Ag nanoparticle and Ni-N-C single atom catalyst in the acidic electrolyte condition. The Ni-N-C was found to have a universally high selectivity of CO2R to CO over HER compared to the Ag nanoparticle, which showed the importance of the catalyst-electrolyte interface on the CO2R activity. This contributes to increased CO2 conversion efficiency even under low concentrations of available CO2 gas. Modulation of the cations and pH can provide new opportunities to promote challenging catalytic reactions.
Method Development and Applications of Online Inductively Coupled Plasma-Mass Spectrometry for Investigating Cathodic Degradation
Authors: Yan Katherine , Lee Sang-Won , Yap Kyra M. K. , Mule Aniket Sandip S. , Hannagan Ryan Travis , Matthews Jesse E. , Lee Dong Un , Burke Stevens Michaela , Nielander Adam C , Jaramillo Thomas F.
Published: December 2024

Online inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for investigating degradation behavior of electrochemical systems in situ. By coupling a potentiostat to an ICP-MS, one can simultaneously probe material degradation and reaction kinetics of electrochemical systems. High instrument sensitivity allows for quantifying trace amounts of degradation down to the parts per trillion range, including non-traditional mechanisms such as nanoparticle loss from bulk materials. In this study, online ICP-MS was used to investigate Au and Cu catalyst degradation via nanoparticle loss in situ during electrochemical CO2 reduction (CO2R). We created a model system to develop the experimental framework and evaluate the strengths and limitations of the technique. This framework was further developed to compare degradation behavior across multiple CO2R catalysts.

Au foil as a CO2R catalyst was used to create a model system. Under CO2R operating conditions in 0.1 M potassium bicarbonate, Au degraded in the form of potential-driven nanoparticle loss. To verify the use of ICP-MS for quantifying nanoparticle detachment, sizes of Au nanoparticle standards were measured by ex-situ ICP-MS, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The size distributions exhibit significant overlap between the three methods. For in-situ degradation experiments, a custom flow-cell design was used to ensure that degradation data was obtained at relevant current densities. We found that under CO2R operating conditions, nanoparticle loss from the Au foil can be induced through pulsing the applied potential. When such a procedure was tested on a Cu foil, both nanoparticle loss and dissolution occurred. In addition to distinguishing between different types of degradation, we used the framework to further probe the degradation mechanisms by modifying the gas environment. The developed experimental framework can be expanded to survey degradation of other electrocatalysts, determine the effects of real-world feedstocks for CO2R on electrocatalyst degradation, and investigate photocorrosion of photoelectrochemical systems.
Confinement Effects on Proton Transfer in TiO2 Nanopores from Deep Potential Molecular Dynamics Simulations
Authors: Kwon Hyuna , Calegari Marcos , Ardo Shane , Esposito Daniel V. , Pham Anh Tuan , Ogitsu Tadashi
Published: December 2024

Understanding proton transfer and water splitting reactions in nano-porous materials is critical for a wide range of emerging technologies, including hydrogen production through photoelectrochemical water splitting. However, elucidating mechanism and energetics of these processes remains a significant challenge for experimental probes. In this work, we combine large-scale molecular dynamics simulations with machine learning potential derived from first-principles calculations to investigate kinetics of proton transfer in nano-porous TiO2 as a representative photocatalyst material. We developed and applied a deep neural network potential to reconstruct the free energy surface of water dissociation and proton transport for a wide range of pore sizes to elucidate confinement effects. Although proton transfer mechanism is similar to that at a TiO2 interface with bulk water, confinement reduces the activation energy of this process, leading to more frequent proton transfer events. This enhanced proton transfer stems from the contraction of oxygen-oxygen distances dictated by the interplay between confinement and hydrophilic interactions. Our simulations also highlight the importance of the surface topology, where faster proton transport is found in the direction where a unique arrangement of surface oxygens enables the formation of an ordered water chain. Our study highlights the critical competition between kinetic and thermodynamic factors introduced by nano-confinement, suggesting potential strategies for optimization of photocatalytic systems for efficient water splitting reactions.