Electrogenerated chemiluminescence (ECL) cells are promising for applications in unique displays due to their simple structure, but further improvements in cell performance have been desired. Herein, we successfully enhanced the luminescent characteristics of the green fluorescent ECL cell by introducing a stilbene derivative as a redox mediator into an anthracene-9,10-diamine derivative solution. 9,10-Bis[phenyl(m-tolyl)-amino]anthracene (TPAA) was used as a luminescent material, while (E,E)-1,4-bis[4-[bis(4-methoxyphenyl)amino]styryl]benzene (TOP-HTM-α1) was used as the mediator. The maximum luminance and current efficiency of the cell with a configuration of indium tin oxide anode/mixed solution/fluorine-doped tin oxide cathode reached 191 cd m⁻² and 1.96 cd A⁻¹, respectively, which are the highest values ever reported in green ECL cells. Moreover, the cell showed a low turn-on voltage (defined as the voltage at 0.01 cd m⁻²) of 2.5 V, which is close to the singlet emission energy of TPAA. We believe that our findings in this study could contribute to the development of advanced ECL display devices.

One of the most critical remaining challenges for extending the lifetime of lithium-ion batteries (LIBs) is the suppression of capacity fading caused by the state-of-charge (SOC) imbalance between the electrodes. Although it has been recognized that side reactions occurring at both the positive and negative electrodes play a crucial role in this degradation process, few theoretical studies have quantitatively related these reactions to battery lifetime. In this work, we formulate the relationship between the rate of side reactions, referred to as the side reaction current (I_SR), and the rate of capacity fading induced by SOC imbalance in LIBs. We first demonstrate that the presence of side reactions establishes local cells within the electrodes, thereby inducing SOC shifts in both the positive and negative electrodes. The types of side reactions responsible for SOC imbalance are then classified and discussed. Furthermore, we describe experimental methods for measuring I_SRs, both those intrinsic to electrode materials and those occurring within LIB cells. Finally, we show that the rate of capacity loss originating from SOC imbalance is governed by the I_SR values of the electrodes and clarify its correlation with conventional lifetime indicators such as Coulombic efficiency and capacity retention. The theoretical framework and equations presented here provide a kinetic basis for analyzing capacity fading caused by the SOC imbalance, offering a unified foundation for evaluating and comparing lifetime improvement strategies in LIBs.

Direct functionalization of benzylic C–H bonds provides an attractive route to access valuable benzylic derivatives, but selective oxidation remains challenging due to overoxidation of the desired products. Herein, we report a new electrochemical strategy for the generation and utilization of benzyl triflates. In this study, benzyl triflates were successfully generated from two-electron oxidation of toluenes, and their formation was directly confirmed by NMR spectroscopy. The anodically generated triflates were subsequently converted into benzylic ethers and thioethers. This approach suppresses overoxidation by generating cationic intermediates under nucleophile-free conditions, which can then be selectively transformed.

The shift towards low-carbon hydrogen via water electrolysis using renewable electricity is crucial for reducing greenhouse gas (GHG) emissions across various industrial sectors. Asahi Kasei, a Japanese chemical company, has leveraged its extensive chlor-alkali electrolysis expertise to develop and demonstrate a large-scale alkaline water electrolysis system, the “Aqualyzer.^†” This paper provides an overview of the core technologies developed for Aqualyzer, including advanced electrolysis components, dynamic control methods, and system simulation technologies. It also details the key test and demonstration facilities, specifically the 10 MW-class system deployed at the Fukushima Hydrogen Energy Research Field (FH2R) and the alkaline water electrolysis pilot test plant comprising four modules in Kawasaki, Japan.

A library of hundreds of metal oxide and metal sulfide photocatalysts has been constructed based on our original strategies of photocatalyst design that were metal cation doping, new valence band formation, and making a solid solution. Various single particulate and Z-scheme photocatalyst systems that are active in visible-light water splitting have been developed. By the doping strategy, SrTiO₃:Rh,Sb and SrTiO₃:Ir,Sb,Al of a single particulate metal oxide photocatalyst were developed for water splitting working under visible light irradiation. BiVO₄ was developed for water oxidation to form O₂ under visible light irradiation by the new valence band formation with Bi6s orbitals. Several types of a Z-scheme system have been constructed by using SrTiO₃:Rh of a H₂-evolving photocatalyst, BiVO₄ of an O₂ evolving photocatalyst, and a suitable electron mediator such as Fe^3+/2+, Co(bpy)₃^3+/2+, reduced graphene oxide (RGO), and poly-3,4-ethylenedioxythiophene (PEDOT). A CuGaS₂-ZnS solid solution photocatalyst was active for sacrificial H₂ evolution, and it was able to be applied to a Z-scheme photocatalyst with BiVO₄ of an O₂-evolving photocatalyst for water splitting without any sacrificial reagents. Novel cocatalysts such as Ag and Rh-Ru were found for photocatalytic CO₂ reduction using water as an electron donor. Ag/NaTaO₃:Ba and Rh-Ru/NaTaO₃:Sr photocatalysts gave 90 % and 10 % of an electron-based selectivity for the CO₂ reduction to form CO and CH₄ accompanied with stoichiometric O₂ evolution even in an aqueous solution under UV irradiation, respectively. A Z-scheme photocatalyst consisting of CuGaS₂-ZnS and BiVO₄ was active for the CO₂ reduction to form CO with 12 % of the selectivity under visible light irradiation in an aqueous suspension system.

We propose an impedimetric biosensor using the bipolar phenomenon with an open bipolar electrode (oBPE). The oBPE platform offers a structurally simple and highly flexible design. The unique electrochemical biosensor consists of a BPE, driving electrodes for detection, and an electrolytic cell as its components. We employed non-faradaic electrochemical impedance spectroscopy to detect biomolecular events occurring on the BPE surface. The biosensor showed a 45 % increase in impedance at 2 kHz after bovine serum albumin adsorption onto the BPE surface. Additionally, the significance of solution resistance, which was uniquely defined by the distance between driving electrodes and a BPE, was demonstrated through changes in impedance. We used the detection system as an immunosensor to detect the binding of C-reactive protein (CRP) to antibody-modified BPE, based on changes in impedance. The biosensor detected the binding of CRP to antibody without the need for redox-active reagents or complex signal amplification steps. The biosensor showed a linear response to the concentration of CRP in the range from 0.001 to 1 µg/mL, comparable to that of conventional three-electrode systems. These findings demonstrate the potential of non-faradaic impedimetric biosensors with an oBPE for sensitive detection of biomolecular events in biochemical analysis.

Thin film solar cells using halide perovskite polycrystals as semiconductors are entering the stage of factory production after their power conversion efficiencies have rapidly improved to 27 %, reaching a level comparable to the highest efficiency of single-crystalline Si solar cells. To ensure stable high efficiency and long device life, further studies on the photovoltaic performance are focused on molecular level improvement of hetero junction interfaces for efficient charge transports. Among inverted p-i-n junction devices which are becoming a major structure in the perovskite photovoltaics, the device using SAMs (self-assembled monolayers) in place of hole transport layer has succeeded in obtaining high efficiencies equivalent to conventional n-i-p devices, Interface molecular engineering, including SAM-based modified interfaces, is essential for reducing charge recombination loss and enhancing photovoltage in power generation. This paper presents research progress on interface engineering for high voltage device performance and our recent efforts to design new structures of perovskite solar cell with SAM-modified hetero-junction interfaces.

Transition metal-doped colloidal quantum dots (QDs) are promising candidates for dual-mode imaging due to their tunable optical properties and potential magnetic functionalities. Here, we report the synthesis and characterization of Mn²⁺-doped AgGaS₂ (AGS) and ZnS-alloyed Ag–Ga–S (AGZS) QDs via a one-pot heating-up method. Upon Mn²⁺ incorporation, both AGS and AGZS QDs exhibited two distinct photoluminescence (PL) peaks originating from the host QDs and doped Mn²⁺ ions, with the relative intensities tunable by varying Mn²⁺-to-total metal cation ratio in the precursor (Mn²⁺/cation_pre). The AGZS QDs prepared with Mn²⁺/cation_pre ratio of 1.1 % exhibited a high PL quantum yield of 45 %, with 40 % of the emission attributed to the d-d transition of Mn²⁺ ions (⁴T₁ → ⁶A₁). Time-resolved PL measurements revealed efficient energy transfer from excitons in the host QDs to doped Mn²⁺ ions, contributing to enhanced Mn²⁺-related emissions. Surface passivation with a ZnS shell followed by ligand exchange with 3-mercaptopropionic acid allowed stable dispersion of AGZS QDs in aqueous media while retaining optical properties. Since the Mn²⁺-doped QDs also exhibited paramagnetic behavior, we investigated the performance of Mn²⁺-doped AGZS QDs as a contrast agent for magnetic resonance imaging (MRI). The intensity of the T₁-weighted MRI signal increased with an increase in the content of doped Mn²⁺. These results demonstrate that Mn²⁺-doped AGZS QDs are promising single-component dual-mode (PL/MRI) nanoprobes for biomedical imaging applications.

A model photocatalyst composed of n-type GaN thin film as a photocatalyst body with a comb shaped electrode composed of Pt layer or Pt/Ti bilayer on the surface was successfully prepared, and photocatalytic and electric properties are investigated. Current-voltage (I-V) curve measurements revealed the formation of Schottky contact between Pt comb and GaN, and ohmic contact between Pt/Ti comb and GaN. In the reaction tests, the GaN model photocatalyst with a Pt/Ti comb showed about three times increased hydrogen evolution rates over the photocatalyst with a solely Pt comb. Under irradiation, about 0.2 V photovoltage at Pt-GaN interface was observed, which prevents electron transfer from the GaN photocatalyst body to Pt cocatalyst, while the photovoltage was eliminated by the introduction of a Ti layer between the Pt and GaN. In-situ photoluminescence (PL) measurement in oxygen ambient confirmed smooth transfer of photoexcited electrons in GaN to Pt/Ti comb, and the degree of quenching indicates efficient charge separation at the working potential. Furthermore, the filling of mid-gap states by electrons was also observed.

Antimony-based sulfide solid electrolytes exhibit high conductivity for alkaline cations. In this study, we synthesized K₃SbS₄ potassium-ion conductors using the mechanochemical method for the nominal compositions with x mol% excess K₂S (x = 0, 5, 10, and 15) to compensate for the chemical impurities in the K₂S reagent. The mechanochemically prepared samples showed X-ray diffraction patterns similar to β-K₃SbS₄ in all the compositions. Raman bands attributed to the SbS₄³⁻ unit were observed in all the samples. The ionic conductivities at 25 °C showed a positive correlation with increasing x, reaching a maximum ionic conductivity of 3.6 × 10⁻⁶ S cm⁻¹ at 10 mol% excess K₂S. Subsequent heat-treatment further enhanced the ionic conductivity, achieving 1.2 × 10⁻⁵ S cm⁻¹ at 25 °C. This improvement is attributed to the nominal composition being close to that of K₃SbS₄ by adjusting the excess amount of K₂S and the increased crystallinity of β-K₃SbS₄.

All-solid-state batteries with sulfide solid electrolytes are promising next-generation energy storage devices owing to their longer lifetimes compared with liquid-type lithium-ion batteries. However, their practical application is hindered by low moisture stability. Few studies have quantitatively compared their moisture stability and underlying mechanisms among electrolyte species. This study systematically evaluates the moisture stability of sulfide solid electrolytes by standardizing particle size and varying electrolyte species, moisture content (dew point), and atmospheric conditions. Sulfide solid electrolytes with different crystal structures, such as Li₆PS₅Cl, Li₃PS₄, and Li₄SnS₄, were exposed to Ar gas flows with dew points from −30 to 0 °C (H₂O concentrations: 0.45–4.8 g m⁻³). H₂S generation followed the order: Li₆PS₅Cl ≫ Li₃PS₄ > Li₄SnS₄. At 0 °C dew point, H₂S gas release was ∼22.7 ml g⁻¹ for Li₆PS₅Cl, ∼0.44 ml g⁻¹ for Li₃PS₄, and ∼0.17 ml g⁻¹ for Li₄SnS₄. Despite variations in H₂S generation, lithium ionic conductivity retention was similar. X-ray photoelectron spectroscopy showed surface hydrolytic decomposition species were observed on Li₆PS₅Cl, whereas Li₃PS₄ and Li₄SnS₄ showed minimal changes. Thermogravimetric analysis revealed clearer hydration in Li₃PS₄ and Li₄SnS₄, causing lower ionic conductivity without H₂S generation. Differences in conductivity reduction are attributed to sulfide unit structures.

A machine learning model that can predict the ionic conductivity of lithium-containing oxides using chemical composition and ionic conductivity data was previously developed. However, this model revealed several limitations, leading to less-than-ideal prediction accuracy. Thus, new models demonstrating improved prediction ability must be developed. This study presents the development of machine learning models for the accurate prediction of ionic conductivity in lithium-containing materials based solely on their chemical composition. The models constructed using the NGBoost and LightGBM algorithms show high compatibility with the training and test data, resulting in high predictive accuracy. The constructed models identify “entropy,” which is considered a key factor in developing ionic conductors, as an important feature. This finding highlights the potential utility of this property from a solid-state chemistry perspective. The developed models demonstrate high predictive accuracy even for previously reported lithium superionic conductor-type materials that were not included in the training dataset. The established models are expected to facilitate efficient material discovery for the development of all-solid-state lithium batteries.

To extend the lifetime of lithium-ion batteries, determining the side-reaction current (I_SR) is essential because capacity fading is mainly caused by the state-of-charge imbalances of positive and negative electrodes. Among the three types of I_SR (intrinsic, additional, and actual), the additional I_SR resulting from crosstalk reactions exhibits complex behavior owing to its dependence on the opposing electrode. In this study, the effect of the opposing electrode on additional I_SR was examined by measuring the three types of I_SR in Li[Li_1/3Ti_5/3]O₄/Li[Li_0.1Al_0.1Mn_1.8]O₄ cells with different capacity ratios of the positive and negative electrodes. The results indicate that additional I_SR correlates with the weight of the opposing electrode, whereas intrinsic I_SR depends on the weight of each electrode. These findings suggest that additional I_SR is closely related to the amounts of side-reaction products generated at the opposing electrode owing to the intrinsic I_SR. The dependence of crosstalk reactions on the concentration of side-reaction products indicates that these concentrations must be considered to extend battery life by adjusting the actual I_SR.

The electrooxidative allylation of a carbamate was successfully demonstrated using 3-propylsulfonic acid-functionalized silica gel (Si-SCX-2). It was shown that the electrochemical oxidation of the carbamate as a first step yields the corresponding N-acyliminium ion equivalent at room temperature, and the reaction of the N-acyliminium ion equivalent with allyltrimethylsilane as a next step leads to allylation without the use of Lewis acids. It was also found that the HBF₄ generated by the cation exchange reaction between the Si-SCX-2 and the supporting electrolyte plays an important role in this reaction system.

Graphene-like graphite (GLG) is capable of reversible intercalation/deintercalation of sodium ions while the interlayer distance is almost the same as that of graphite, and elucidation of this factor will provide important insights into the design guidelines for anode materials for sodium-ion batteries. We focused on oxygen-containing functional groups in GLG and investigated their effect on the sodium ion intercalation potential using density functional theory calculations. It was found that the intercalation potential of sodium ions increased significantly in models containing lactones and ketones, leading to the formation of the low-stage intercalation compounds at higher potentials compared to sodium metal deposition reaction. In addition, it was suggested that the introduction of these functional groups changed the electronic state of the materials to increase electron acceptability, which contributed to the increase in potential. Furthermore, the negatively charged oxygen atoms interacted electrostatically with sodium ions, which to some extent had a positive effect on increasing the reaction potential. From these results, it was concluded that the oxygen-containing functional groups in GLG play a crucial role in the performance as anode materials of sodium-ion batteries.

Toward decarbonized society with sustainable growth, the use of renewable energy as a primary power source is highly demanded. Water electrolysis is promising to produce hydrogen from renewable energy for energy storage and transportation. In developments of new technologies related to alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE), common measurement techniques are required to compare experimental results fairly among different institutes. In this paper, we introduce common measurement techniques, such as electrochemical half cell and full cell for AWE and PEMWE, evaluation techniques for catalytic activities and durability of catalysts under steady and non-steady operation, advanced synchrotron radiation analysis of catalysts, operando XAFS analysis, and optical observation of gas bubbles in detail, that are recently developed in the project research commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

PtNi alloy catalysts exhibit shape-dependent oxygen reduction reaction (ORR) activity and durability, influenced by synthesis conditions. In this study, a standardized synthesis method was developed by controlling the heating rate during nanowires (NWs) formation, yielding three distinct PtNi NW catalysts. Among these, PtNi-NW-3, featuring a rough surface with abundant high-index facets, demonstrated exceptional ORR activity and durability, achieving a mass activity of 1.06 A mg_Pt⁻¹ and a specific activity of 2.73 mA cm_Pt⁻², outperforming commercial Pt/C catalysts. The superior performance was attributed to reduced oxygen-binding energy and suppressed Pt oxidation, as revealed by operando high-energy-resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS). This work not only standardizes NW synthesis for improved reproducibility but also provides critical insights into the relationship between structural features and catalytic behaviours, paving the way for next-generation electrocatalysts.

Crystalline silicon solar cells have become the leading technology in solar cell manufacturing. However, conventional solar cell manufacturing methods are energy-intensive and inefficient. We previously developed an electrodeposition method that improved crystalline Si film production but faced limitations in grain size, which is crucial for minimizing recombination losses in polycrystalline Si solar cells. In this study, the co-deposition of Si and Zn on a graphite substrate is investigated to obtain large grain-sized Si films. Electrochemical measurements and electrolysis are conducted at 923 K in molten KF–KCl–K₂SiF₆–ZnCl₂ systems. Reduction currents corresponding to the reduction of Zn(II) and Si(IV) ions are observed at approximately −2.6 V vs. Cl₂/Cl⁻ and −3.1 V, respectively in the cyclic voltammogram on a glassy carbon electrode. The optimal conditions for obtaining highly crystalline Si films are investigated by varying the ZnCl₂ concentration and current density. During co-deposition, a Si–Zn liquid alloy is deposited. Post-electrodeposition cross-sectional images reveal a Si layer on the graphite substrate with a Zn layer on top. After Zn removal, the Si films exhibit larger crystal sizes than those obtained without ZnCl₂, indicating deposition through liquid alloying with Zn.

Metal-assisted etching (metal-assisted chemical etching) is increasingly recognized as a crucial method for fabricating silicon (Si) nanostructures. This process involves the dissolution of Si both directly beneath metal catalysts (local etching) and at locations away from them (remote etching). We previously investigated general corrosion, a kind of remote etching, in metal-particle-assisted etching of moderately-doped n-Si and explained its mechanism in platinum-assisted etching where a sponge-like porous layer was observable on the top surface of Si, which dissolves spontaneously. However, general corrosion caused by gold (Au)-assisted etching has not been explained yet, as the soluble layer was not clearly observed. It is also difficult to explain why general corrosion was suppressed in silver (Ag)-assisted etching under the conditions we examined. In this work, we estimated the depth of general corrosion caused by Au- and Ag-nanoparticle-assisted etching of moderately-doped p-Si and n-Si based on the etched structures and mass loss of substrate. We also discussed etching behavior based on polarization curves of bare Si, metal-deposited Si, and metal wires. This work provides insights into the underlying mechanism of remote etching and proposes a potential strategy to mitigate it.

An electrical conductivity and its activation energy are measured for solid-liquid coexistence systems consisting of TiO₂ powder/highly concentrated LiTFSA aqueous electrolyte (20.5 mol kg⁻¹). The conductivity increases exponentially with an increase of the liquid content up to ca. 40 vol%, and the activation energy of the conductivity increases with a decrease of the liquid content below 35 vol%. Various spectroscopic measurement, such as Raman, near-infrared (NIR), and NMR spectra indicated that the presence of TiO₂ disrupts the nanoscale water channel structure in the water-enriched regions of the bulk solution in the TiO₂ powder/20.5 mol kg⁻¹ LiTFSA solid-liquid coexistence system with a liquid phase volume fraction below 40 vol%, resulting in an unusual decrease in the electrical conductivity. The strong influence of the solid phase on the electrical conduction of the highly concentrated LiTFSA electrolyte was found to be significant only in the region below 50 vol% in the liquid content, while in the region of the liquid content above 50 vol%, there were no differences due to electrolyte concentration and ion species, indicating the influence of the solid phase on electrical conduction.