To develop molten salt electrolytes for Al electrodeposition, part of AlCl₃ in the AlCl₃–NaCl–KCl molten salt was replaced with AlBr₃ at concentrations of 3, 6, and 9 mol%. The melting point decreased with increasing AlBr₃ concentration, reaching a reduction of 20 °C at 9 mol% compared with the chloride-only molten salt. Electrodeposition of Al was conducted using the bromide-containing molten salts at a constant current density of 40 mA cm⁻². During electrolysis, both the anode and cathode potentials remained constant for 5000 s. The morphology of the Al deposited on the cathode was observed, and its surface roughness was measured using a laser microscope. The measurements indicated a trend toward reduced surface roughness with increasing AlBr₃ concentration. The chloride molten salts containing AlBr₃ exhibited lower melting points and improved the surface morphology of the electrodeposits.

Quinone-based molecules provide promising electrode materials for energy-storage devices; however, their redox reaction kinetics are typically slow because the process is governed by mass transfer. The micropore confinement of quinone-based molecules exhibits anomalous pseudocapacitive behavior owing to the characteristic adsorption potentials of micropores. In addition, a highly crystalline carbon surface enhances redox reversibility through strong π-π interactions. This study investigated the effects of surface crystallinity on redox reversibility utilizing a carbon mesosponge comprising single-layer graphene with a crystalline carbon surface. The carbon mesosponge improved the redox reaction despite its mesoporous nature. This result can be attributed to the large amount of adsorbed molecules on the micropore surface and the incorporation of single-layer graphene within the framework.

It is important to develop a rechargeable battery that is safe and free from resource risk to replace the current lithium–ion battery in various application fields. We have been conducting research and development of aqueous electrolyte batteries with zinc as the negative electrode (anode) through national programs, Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING, RISING2 and RISING3), commissioned by the New Energy and Industrial Technology Development Organization (NEDO). In RISING2, we demonstrated a full cell that can achieve a target specific energy of 500 Wh kg⁻¹ for a zinc–air system through advancements in elemental technology and full-cell engineering. RISING3 aims to develop a sealed zinc-anode rechargeable battery by developing positive electrode (cathode) materials to replace air electrodes. A notable achievement of this study is proving that the manganese dioxide (MnO₂) prepared through electrolysis (EMD) has good rechargeability in alkaline electrolyte systems, in which the amount of structural water in the oxide determines the discharge capacity for the first one-electron reduction. We also found that the newly developed MnO₂ from the chemical reduction of permanganate (PMD) enables a reversible two-electron reaction even in the electrolyte containing zinc species, in which hetaerolite (ZnMn₂O₄) generally forms to inhibit further electrochemical reactions.

Suppressing zincate crossover is necessary for rechargeable alkaline Zn-MnO₂ rechargeable batteries using electrolytic manganese dioxide (EMD). We benchmarked six commercial separators for their ability to block zincate ions while maintaining the transport of hydroxide ions. Among the separators, FAAM-75-PK (FP75), a commercial anion-exchange membrane, exhibited moderate conductivity (5.8 mS cm⁻¹) with the lowest diffusion coefficient of zincate ions (D_Zn = 2.0 × 10⁻⁸ cm² s⁻¹) and a moderate diffusion coefficient of hydroxide ions (D_OH = 3.5 × 10⁻⁵ cm² s⁻¹), leading to the highest permselectivity (D_OH/D_Zn = 1.7 × 10³). In the galvanostatic discharge–charge tests, FP75 exhibited the best capacity retention of 68 % at the 7th cycle. Characterization of the discharged EMD electrodes revealed that FP75 effectively suppressed ZnMn₂O₄ formation at the cathode, favoring Mn₃O₄ formation instead. The low Zn concentration of 6 ppm in the catholyte is consistent with the favored Mn₃O₄ formation. Beaker-cell tests identify a system-dependent zinc concentration threshold. When the Zn/Mn molar ratio exceeds ∼0.05–0.15, product formation shifts toward ZnMn₂O₄ from Mn₃O₄, and thus, the capacity decay accelerates.

Homogeneous surface-enhanced Raman spectroscopy (SERS) substrates are critical for quantitative analysis but remain challenging to fabricate at scale. This study established a hybrid nanoimprint lithography and galvanostatic pulse electrodeposition strategy to fabricate scalable Ag–Au alloy SERS substrates with remarkable signal uniformity. By systematically optimizing pulse parameters, such as current, duty ratio, and deposition bath composition, including the Ag⁺/Au³⁺ ratio and the presence of thiourea additive, we achieved the uniform filling of nanoarrays with Ag–Au alloy nanoparticles with an optimal Ag content for the SERS enhancement effect. The Ag–Au SERS substrate prepared under the optimized conditions with 71 at% Ag displayed a high enhancement factor on the order of 10⁶ and a record-low signal variability with a relative standard deviation of 6.8 % throughout the mapping area, surpassing sputtering-based Ag SERS substrates. This approach combines top-down patterning with bottom-up electrochemical growth, thereby offering a cost-effective path for fabricating reproducible plasmonic substrates for electrochemical analysis and environmental monitoring applications.

An electrochemical circuit containing a control unit is used to control the interfacial potential difference between the bipolar electrodes (BPEs) and the electrolyte solution in an open bipolar system. The control unit consists of a polymeric Na⁺ ion-selective electrode (ISE) connected to a BPE and an Ag/AgCl wire, which connects the electrolyte solution in the control unit to the main chamber via the BPEs. The BPEs contain openings with exposed platinum areas, which serve as cathodic and anodic poles and a potential-determining element. The interfacial potential difference between the potential-determining opening (PDO) and the electrolyte solution can be determined by applying Kirchhoff's second law to the closed circuit containing the PDO, ISE, and Ag/AgCl wire. In the open bipolar system, the intensity of the electrochemiluminescence signal measured for analysis varies depending on the position of the opening of the BPEs. The results suggest that the interfacial potential difference between the anodic and cathodic poles can be varied with a control unit by avoiding ionic crosstalk.

The polarity reversal operation of a symmetric battery —a strategy uniquely enabled by identical electrodes— using NASICON-type Na_2.5V_1.5Ti_0.5(PO₄)₃ electrodes in a highly concentrated aqueous sodium trifluoroacetate electrolyte was examined to gain insight into the inherent asymmetric properties that develop during unidirectional charge-discharge cycling. The asymmetrically grown electrode-electrolyte interfaces (EEIs) at both electrodes exerted persistent effects on subsequent reversely directed charge-discharge cycles following electrode switching, whereas the electrolyte pH split responded rapidly. A certain number of repeated charge-discharge cycles in the same direction was required to form a robust EEI tolerant to drastic pH changes. Polarity reversal operation combined with occasional electrode switching may promote quasi-symmetric EEI formation on both electrodes, which could be beneficial for improving cyclability and coulombic efficiency.

Measuring the local potential distributions in oxygen electrodes, such as bifunctional air electrodes for metal-air secondary batteries and cathodes for fuel cells, is crucial for understanding reaction processes and for developing electrode design guidelines. In this study, we explore indicators for optically visualizing the local potential in alkaline oxygen electrodes. Ni, Ag, and Cu are selected as potential indicators, and their brightness changes depending on applied potentials were measured by using a confocal optical microscope in aqueous solutions of 1.0 mol dm⁻³ and 8.0 mol dm⁻³ KOH. The brightness of Ni, Ag, and Cu foil electrodes (thickness: 30 µm) decreases/increases with oxidation/reduction at around the oxygen evolution reaction potential (1.22–1.42 V vs. RHE), the equilibrium potential (1.12–1.22 V vs. RHE), and the oxygen reduction reaction potential (0.62–0.77 V vs. RHE) regions, respectively, demonstrating that these materials can function as potential indicators for alkaline oxygen electrodes. Furthermore, Ni and Ag microwire electrodes (diameter: 50 µm), which are supposed to have less effect on mass transport than the metal foil electrodes, also show brightness changes similar to those of the metal foils in 8.0 mol dm⁻³ KOH.

Rechargeable zinc-air batteries (r-ZABs) are excellent candidates for next-generation secondary batteries due to their high energy densities and safety; however, they have issues of electrolyte volatilization, leakage, and side reactions at the air electrode caused by zincate ([Zn(OH)₄]²⁻) diffusion. A gel polymer electrolyte (GPE) consisting of a polystyrene-based densely crosslinked network structure bearing quaternary ammonium anion exchange groups at the crosslink points was developed. The GPE showed higher monovalent anion conductivity and lower divalent anion ([Zn(OH)₄]²⁻) diffusion coefficient than a conventional anion exchange membrane and a porous separator due to the network structure with high ion exchange capacity (IEC) of the novel GPE. The charge-discharge r-ZAB test using the GPE demonstrated higher cycle stability than a liquid electrolyte due to enhanced ion conductivity and suppressed diffusion of [Zn(OH)₄]²⁻, as well as sufficient mechanical toughness of the densely crosslinked network structure.

Two-dimensional (2D) metal microstructures are widely used in advanced electronic and optoelectronic devices, however, their low-cost and high-efficiency patterned fabrication remains a significant challenge. This study developed a maskless and flexible light-induced electrochemical deposition (LED) method for the 2D patterned deposition of Cu on the surface of hydrogenated amorphous silicon (a-Si:H) coated conductive glass. The study systematically has investigated the influence of key parameters (e.g., deposition potential, electrode gap, and light source) on the deposition process, has successfully fabricated complex Cu micro-patterns with clear feature edges and dense morphology, and the specific composition of the sediment was analyzed by X-ray diffraction (XRD). The as-prepared microstructures exhibit a maximum dimension of less than 200 µm, and the minimum characteristic dimension of the deposited structures is 10 µm. This work realizes low-cost fabrication of 2D microstructures via a commercial projector. This study confirms the feasibility and superiority of LED technology in direct writing of 2D metal patterns, providing a promising low-cost solution for the rapid manufacturing of components such as flexible circuits and metal grid transparent electrodes.

H-type divided electrochemical cell is an important experimental apparatus for electro-organic synthesis by using reactive species, which is generated on the surface of the anode or the cathode. However, the preparation of H-type divided electrochemical cell at the laboratory level was expensive and not cheap. In this paper, we propose the insertion of cylinder tube equipped with the glass filter into sample tube, in order to enable anyone to easily and affordably achieve a divided electrochemical cell in organic synthesis.