The cover art is attributed to an article entitled “Advances of Perovskite Solar Cells: Interface Engineering to Achieve High Photovoltage Performance” by Prof. Tsutomu Miyasaka et al. selected as an Editor’s Choice for the 72nd Special Feature, “Research Frontiers of Photoelectrochemical Energy Conversion and Photocataly­sis” recommended jointly by the guest editors from The Photoelectrochemistry Research Group and the editorial board. It synthesizes and advances a rapidly industrializing field: halide-perovskite thin-film photovoltaics now achieving 27% power conversion efficiency, rivaling single-crystalline Si. The authors present compelling evidence that interface molecular engineering—especially SAM-modified heterojunctions in inverted p-i-n architectures—delivers efficiency on par with conventional n-i-p devices and lead to cost reduction with simplified layer structures. The work combines clear mechanistic insight with practical design rules and proposes new device structures directly relevant to scalable manufacturing and long-term stability. Its originality, rigor, and translational impact make it an outstanding contribution worthy of recognition. This cover art was created and published with financial support from The Electrochemical Society.

The cover art is attributed to an article entitled “Tuning Photoluminescence and Magnetic Properties of Ag–Ga–S and Zn–Ag–Ga–S Quantum Dots via Mn²⁺ Doping” by Chang Jiang et al. selected as an Editor’s Choice for the 72nd Special Feature, “Research Frontiers of Photoelectrochemical Energy Conversion and Photocatalysis” recommended jointly by the guest editors from The Photoelectro­chemistry Research Group and the editorial board of Electrochemistry. In this article, the authors report the first synthesis of Mn²⁺-doped AgGaS₂ and Ag–Ga–Zn–S quantum dots (QDs) via a one-pot method. These QDs were low in toxicity, and the Mn²⁺-doping improved their photoluminescence quantum yield to as high as 45%. The doping also rendered the QDs paramagnetic and readily detectable by magnetic resonance imaging (MRI). Therefore, those QDs are promising as nanoprobes for both photoluminescence- and MRI-based bioimaging.

The article entitled “Effects of ohmic contact formation between GaN photocatalyst and Pt cocatalyst” by Takaya Ochiai et al. selected as an Editor’s Choice for the 72nd Special Feature, “Research Frontiers of Photoelectrochemical Energy Conversion and Photocatalysis” recommended jointly by the guest editors from The Photoelectrochemistry Research Group and the editorial board of Electrochemistry. In this article, the authors have investigated GaN thin films as a model photocatalyst system and successfully monitored the electrode potentials of GaN and cocatalysts under light irradiation in aqueous media. Notably, the use of a Pt/Ti bilayer cocatalyst was found to eliminate the Schottky barrier between GaN and Pt, resulting in the formation of an ohmic contact. The insights provided by this article into the electric interactions at the semiconductor/cocatalyst interface under operational conditions is highly valuable for the research in photocatalytic and photoelectrochemical water splitting.

Electrochemistry overhauled its Instructions for Authors, assigned a new DOI, and aligned with the Principles of Transparency and Best Practice in Scholarly Publishing (COPE/DOAJ/OASPA/WAME). The revision codifies policies on ethics, copyright, governance, fees, peer review, and accessibility/DEI (Diversity, Equity, and Inclusion) to strengthen credibility and accountability. The editorial board also recognize a countervailing risk: lengthy, prescriptive guidelines can burden authors and delay publication. Evidence from surveys and audits supports format-free initial submission; major publishers now allow relaxed first submissions. Electrochemistry already accepts free-format manuscripts and does not desk-return for reference style etc. The Editorial Board of Electrochemistry will present policies more clearly and streamline workflow while maintaining rigorous transparency. Additionally, the winners of the ECSJ awards in 2024 are introduced of which comprehensive papers were issued in Vol. 92, No. 10.

Photoelectrochemical strategies offer promising pathways for both solar-to-electricity and solar-to-chemical conversion. Advances in functional materials and devices, including solar cells, photocatalysts, plasmonic materials, quantum dots, and electrocatalysts, have significantly broadened the scope of the field. The 72nd Special Feature of Electrochemistry, “Research Frontiers of Photoelectrochemical Energy Conversion and Photocatalysis,” covers a wide range of state-of-the-art topics of photoelectrochemistry, highlighting recent progress and emerging trends in electrochemical solar energy conversion.

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.

Plasmon-induced charge separation (PICS), which occurs at the interface between metal nanoparticles exhibiting localized surface plasmon resonance (LSPR) and semiconductors, has attracted attention as a promising method for extracting photoenergy as electric charge. Although n-type semiconductors have been the standard, p-type semiconductors are now being explored for their potential to enhance stability and catalytic performance. In this study, RuO₂ and IrO₂ were selected as p-type semiconductors and combined with Ag nanoparticles (AgNPs) to investigate the effects of their conductivity and band gap on the charge separation efficiency. As a result of evaluating the charge separation efficiency as photocurrent using an all-solid-state cell, an incident photon-to-current efficiency (IPCE) of ∼0.15 % was achieved in the system using IrO₂, which has high conductivity and the plasmon absorption band and its own photon absorption band do not overlap. This is the highest conversion efficiency in all-solid-state cells utilizing the p-type PICS mechanism. This achievement provides an effective guideline for the design of materials for further improvement of efficiency as well as for applications such as photodetectors, photoelectric conversion devices, and photocatalysts.

Considering that the simplicity of photodeposition and impregnation limits the controllable parameters during deposition, we investigate a deposition process utilizing galvanic replacement to achieve diverse deposition states of Pt cocatalysts. Various Pt nanoparticle morphologies are successfully obtained using Ag, Cu, and Bi as mediator metals. Among these, Pt nanoparticles loaded via Cu mediation exhibit high dispersion and demonstrate superior hydrogen evolution activity compared with those prepared by the conventional photodeposition method. Although using Ag and Bi results in the formation of byproducts such as AgCl and BiOCl, we demonstrate an effective deposition strategy to suppress or eliminate these byproducts. These findings suggest that the controlled deposition of diverse metal nanoparticles is beneficial for the hydrogen evolution reaction and offers considerable potential for broader applications in photocatalytic reactions, heterogeneous catalysis, and optical materials.

TiO₂ as a semiconductor photocatalyst has been extensively utilized in the purifications of water and air. However, the wide band gap of TiO₂ necessitates its activation by ultraviolet irradiation, when it is utilized as a photocatalyst. To enhance the photocatalyst performance of TiO₂, constructing the heterojunction containing TiO₂ is considered as a highly effective method. To unfold the actual application, iron metal oxides are firstly utilized to construct the heterojunction of TiO₂/α-Fe₂O₃, and the synthesized TiO₂/α-Fe₂O₃ heterojunction was successfully coated on the surface of coal tar pitch based spherical activated carbons (CTP-SACs). The structures of TiO₂/α-Fe₂O₃/CTP-SACs are verified by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results of UV-vis absorption spectroscopy supports that TiO₂/α-Fe₂O₃/CTP-SACs are promising candidates for the natural light photoncatalysis. It is believed that the exceptional conductivity of CTP-SACs enhances the activity of the photocatalyst, resulting in the TiO₂/α-Fe₂O₃/CTP-SACs exhibiting remarkable sterilization effects under natural light. For instance, the TiO₂/α-Fe₂O₃-60-CTP-SAC shows an excellent sterilization rate (89 %) for the fish culture water under the irradiation of natural light for 20 min. Associating with the excellent liquidity of CTP-SACs, it is considerable that TiO₂/α-Fe₂O₃/CTP-SACs possess the captivating application prospects in a field of the feeding water treatment.

Chiral plasmonic nanostructures attract attention recently, and one of the promising methods for chiral shaping is photoelectrochemical growth of the nanostructures under circularly polarized light (CPL). The CPL-induced method has been based on asymmetric and twisted electric field distribution generated around anisotropic plasmonic nanoparticles irradiated with CPL. In the present work, isotropic and symmetric Au nanodisks were used as plasmonic precursors, around which uniform electric fields were generated. When the Au nanodisks were irradiated with CPL in the presence of Ag ions and citrate ions, initial Ag deposition at an arbitrary site broke the symmetry, and gave rise to anisotropic and asymmetric electric field distribution, which leads to chiral shaping of Au-Ag nanostructures and chiroptical responses.

Electrochromic windows are promising devices for efficiently controlling transmission of light and heat through windows in order to suppress energy consumption of buildings. In particular, versatile electrochromic windows operating in the bright, cool, and dark modes attract attention. In the present work, we synthesized amorphous oxygen-deficient WO_3−x nanoparticles and Cu-doped NiO nanoparticles by simple and convenient methods and assembled an electrochromic cell by using the nanoparticles. In the bright mode at +1.0 V, the cell transmitted ∼90 % visible light at 500 nm and ∼80 % near infrared (NIR) light at 1000 nm, whereas the transmittance was suppressed to 10–20 % in both of the visible and NIR ranges in the dark mode at −3.0 V. In the cool mode at −2.5 V, the cell showed a marked contrast in the optical transmittance: ∼90 % in the visible and ∼20 % in the NIR range. The oxygen deficiency of the WO_3−x cathode and/or the Cu doping of the NiO anode led to the high visible-NIR transmittance contrast in the cool mode, in addition to excellent cyclability at least for 12000 cycles and improved coloration efficiencies in the visible and NIR ranges.

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.

The rational design of heterojunction Z-scheme photocatalysts with controlled particle alignment is critical for improving the efficiency of overall water splitting. In this study, we report the fabrication of a Z-scheme photocatalyst composed of Bi₄V₂O₁₁ (BVO), Au nanoparticles and ZnRh₂O₄ (ZRO), with a focus on spatially aligning the constituent particles via an electrostatic assembly method. The surface of BVO was functionalized with 3-aminopropyltrimethoxysilane (APTMS) to promote the uniform deposition of Au nanoparticles, which subsequently enabled the anchoring of ZRO particles, forming a well-aligned heterojunction photocatalyst (BapAcZ). Structural and spectroscopic analyses confirmed the successful formation of the ternary composite with embedded Au between BVO and ZRO. Photocatalytic tests under monochromatic light at 700 nm revealed that BapAcZ exhibits significantly higher activity and reproducibility than randomly assembled composites, achieving an apparent quantum efficiency (AQE) of 4.7 × 10⁻² %, which is 1.8 times that of the control sample. These findings highlight the importance of particle-level structural engineering in designing efficient Z-scheme systems for solar water splitting and provide insights for further development of multi-component photocatalytic systems with precisely controlled architectures.

Photoelectrodes based on plasmon-induced charge separation (PICS) often consist of Au nanoparticles (NPs) supported on an n-type semiconductor electrode and work as photoanodes. Meanwhile, there are fewer studies on plasmonic photocathodes fabricated by coating a plasmonic NP-modified electrode with the semiconductor. In the present study, plasmonic photocathodes in which Ag NPs electrodeposited on an indium tin oxide (ITO) electrode are covered with TiO₂ (ITO/Ag/TiO₂) were fabricated via a spray pyrolysis method. The photocathode exhibited efficient absorption and photocurrent responses derived from quadrupolar localized surface plasmon resonance (LSPR) mode. Since there are few studies on the ITO/Ag/TiO₂ photocathode and the quadrupole mode shows a smaller scattering/extinction ratio and longer lifetime than the dipolar mode, the insights obtained in the present study would lead to the design of highly efficient plasmonic photocathodes.

Localized surface plasmon resonance (LSPR) in metal nanostructures generates intense, spatially confined electric fields. At the present stage, direct experimental evidence for LSPR-induced perturbations at solid–liquid interfaces remains limited. In this study, we utilize near-infrared spectroscopy to monitor overtone and combination vibrational modes of H₂O/D₂O mixtures, which reflect hydrogen bonding networks, in the presence of colloidal Au nanoparticles under LSPR excitation conditions. Notably, spectral changes were observed exclusively in isotopically mixed H₂O/D₂O solutions (1 : 1 volume ratio) under LSPR excitation. The power and wavelength-dependent spectral variations—most prominently observed at 6900 cm⁻¹, corresponding to the first overtone of the O–H stretch—indicate a selective modulations of HOD vibrational modes. Spectral deconvolution reveals that LSPR predominantly perturbs H-D interactions rather than H-H or D-D interactions. These findings highlight an isotope-selective, field-driven reorganization of the interfacial hydrogen bond network, which may contribute to the anomalous kinetic isotope effects observed in plasmon-induced reactions.

Bismuth chalcohalides (Bi–S–X, where X = Cl, Br, or I) are promising candidates for photovoltaic and optoelectronic applications due to their low toxicity, narrow bandgaps, and solution processability. Here, we report a colloidal synthesis of Bi₁₃S₁₈I₂ nanorods (NRs) with tunable widths ranging from 7 nm to 44 nm. Surface modification with 3-mercaptopropionic acid (MPA) enabled the resulting NRs to disperse uniformly in aqueous solution, free from by-products. By varying synthesis temperature, the bandgap can be systematically engineered from 1.67 eV to 1.31 eV due to the quantum size effect. The NRs exhibit broad visible-to-NIR absorption, and retain their optical and structural integrity after ligand exchange with MPA for aqueous dispersion. This approach was extended to synthesize Bi₁₃S₁₈(Br,I)₂ alloy NRs, whose composition was tuned by varying the I/(I + Br) precursor ratio. The resulting alloyed NRs maintained a similar morphology, the width of 6–8 nm and the length of 250–300 nm, regardless of their composition, but their absorption spectra tended to be blue-shifted with an increase in the I content. Photoelectrochemical measurements revealed n-type semiconductor behavior, with photocurrent generation under visible and NIR illumination. This study establishes a versatile synthetic framework for engineering composition, morphology, and electronic structure in bismuth chalcohalide NRs for environmentally friendly optoelectronic device applications.

Water electrolysis in alkaline conditions is one of the major processes for green hydrogen production. The overpotential of the oxygen evolution reaction (OER) is generally higher than that of the hydrogen evolution reaction (HER). Therefore, understanding the origin of the OER mechanism in alkaline conditions is important. Here, we utilized Raman spectroscopic analysis and machine learning techniques to study the OER from a Ni electrode to probe the OER intermediates in alkaline conditions. Raman spectroscopy was conducted using objective lenses with long working distance to avoid the damage of lens by alkaline electrolytes. This developed method can be used for the observation of the OER intermediates of Ni even in strong alkaline electrolytes. Raman mapping analysis revealed the variation of OER intermediates, which can be additional proof of the hidden reaction pathway from machine learning analysis. This study can be utilized as a methodology for the understanding of the multi-electron transfer reaction from the electrochemical and spectrochemical analyses.

Here we report the synthesis of branched platinum nanoparticles (Pt NPs) and the evaluation of their performance as a catalyst for the oxygen reduction reaction (ORR). The morphology of the branched Pt NPs could be easily controlled from one dimensional (1D) to three dimensional (3D) by the concentration of L(+)-ascorbic acid (AA) used for the synthesis. The surface-specific activities of the product prepared at 8.0 mmol L⁻¹ AA was four times higher than that of a commercial standard catalyst. Our method could be extended to the development of higher efficient Pt NP catalysts for the ORR including photoelectrochemical systems.

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.

This study investigates the effect of the contact time of chlorobenzene, when used as an antisolvent, on the formation of perovskite layers during spin-coating. The contact time of chlorobenzene is controlled by adjusting the drop rate and dispensing volume using an apparatus developed in our laboratory that combines a spin coater and micropipette. X-ray diffraction (XRD) results show no significant change in the crystal structure of perovskite when chlorobenzene is added in the contact time range of 0.3 to 2.0 s, during the spin-coating preparation using the antisolvent method. However, as the contact time with chlorobenzene increases, the grain size decreases, and the power conversion efficiency (PCE) also decreases accordingly. Reducing the drop rate, regardless of the amount of chlorobenzene used, allows sufficient time for the formation of larger crystals, thereby improving the PCE. These results highlight the importance of controlling the contact time with the antisolvent to optimize solar cell performance.

To enable fast charging in lithium-metal anode all-solid-state batteries, the suppression of lithium dendrite formation at the solid electrolyte (SE) interface is critical. Gold (Au) sputtering has been proposed to enhance interfacial contact and mitigate dendrite growth; however, conventional sputtering can thermally damage the SE and degrade its fracture toughness. In this study, we investigated magnetron sputtering as a low-damage deposition technique for applying Au interlayers. The magnetically confined plasma in magnetron sputtering minimizes the surface exposure and thermal degradation of the SE, potentially preserving its mechanical integrity. Lithium garnet-type SEs with and without shot peening (SP) were prepared and coated with Au via normal and magnetron sputtering. Critical current density (CCD) and fracture toughness were evaluated for each condition. Without SP, CCD improvement was limited and independent of the sputtering method. In contrast, with SP, CCD was significantly enhanced, and magnetron sputtering yielded a higher CCD than normal sputtering. Fracture toughness measurements revealed that thermal damage from normal sputtering reduced toughness, whereas magnetron sputtering preserved it. These results demonstrate that combining SP with magnetron sputtering effectively improves the SE interfacial properties, thereby enhancing the fast-charging capability.

Solid electrolytes are important for realizing all-solid-state lithium batteries and improving their performance. In this study, lithium-ion conducting glasses and glass-ceramics in the pseudo-ternary system Li₃PS₄–Li₄SnS₄–LiI are prepared using the mechanochemical method and subsequent heat treatment. The glass-ceramic 67(0.75Li₃PS₄·0.25Li₄SnS₄)·33LiI (mol%) electrolyte exhibits a high conductivity of 6.8 × 10⁻³ S cm⁻¹ at 25 °C because of the precipitation of a Li₁₀GeP₂S₁₂ (LGPS)-analog phase. The LGPS-analog phase is formed by adding LiI to the Li₃PS₄–Li₄SnS₄ system. An all-solid-state cell developed using a glass-ceramic electrolyte operates stably at room temperature.

Sulfur positive electrodes in liquid-type lithium–sulfur (Li–S) batteries exhibit two discharge plateaus at approximately 2.4 and 2.1 V (vs. Li). However, conventional sulfur composite electrodes in all-solid-state Li–S batteries typically do not display these two clear discharge plateaus. Furthermore, the reaction mechanisms in such frameworks remain poorly understood. In this study, the cause of these differences and reaction pathways were clarified by examining the reaction progression and distribution through the electrode thickness using hard X-ray photoelectron spectroscopy, Raman spectroscopy, and incremental capacity analysis (ΔQ/ΔV). The results indicate that the reaction proceeds from neutral bridged sulfur to Li₂S via lithium polysulfides with Li-coordinated anionic sulfur, similar to liquid type ones. Furthermore, clear differences in the reaction progression across the electrode thickness are observed. In low-reactivity electrodes, the degree of reaction progress varies more significantly across the thickness compared with that in highly reactive electrodes. This suggests that in low-reactivity sulfur composite electrodes, the two-plateau reactions proceed simultaneously throughout the discharge region. In contrast, high-reactivity electrodes show clear discharge plateaus, with regions in which only the second plateau reaction occurs. These insights will accelerate further understanding of the reaction for all-solid-state Li–S batteries.

The authors worked as working group members in molten salt committee in FY 2020–2024 to collect the books and literatures devoted to the data of precious metal salts. They cover basic properties, phase stability, activity coefficient, complexes, and electrochemical data. Due to the easy decomposition of the compounds, several literatures report not their single properties but their properties in molten salts. We hope that this activity report contributes to the committee members developing the processes of production or recovery of precious metal using molten salts.

We propose new concept of capillary covered carbon felt electrodes in small scale of electro-organic synthesis. Capillary covered carbon felt electrode could be made by placing a couple of carbon felts in a pasteur pipette and heating them with a gas burner to stretch the glass. When it was cooled to room temperature, the electrode was prepared by cutting it to the desired length. The present electrode we propose here is more robust than fragile pencil leads, and is therefore effective for electrochemical synthesis in small sizes. Although the distance between electrodes using naked carbon felts might be changed under stirring due to threads, the distance between electrodes could be fixed by using the present electrodes under electrolysis.