Editor’s Choice of this issue is an article entitled “Mixed Solution System Containing Anthracene and Stilbene Derivatives for an Efficient Green Fluorescent Electrogenerated Chemiluminescence Cell” by Prof. Takashi KASAHARA et al. In this article, the authors significantly enhance the performance of green fluorescent electrogenerated chemiluminescence (ECL) cells by integrating the well-designed redox mediator into an anthracene-9,10-diamine-based luminescent system. ECL cells gain a significant attention for practical display applications owing to their remarkable processabilities. To enhance the luminescent performance of ECL to meet the global demands, the authors herein introduced the rationally designed stilbene-derived redox mediator into a benchmarking anthracene-diamine luminescent system. The optimized device delivers record-high luminance and current efficiency, together with an exceptionally low turn-on voltage approaching the intrinsic emission energy of the emitter. The work not only establishes a new performance benchmark for green ECL cells but also elucidates the effectiveness of mediator engineering as a powerful strategy for enhancing ECL efficiency. The findings represent a meaningful step toward practical high-performance ECL display technologies.

The cover art of this issue is attributed to an article entitled “Formulation of Capacity Fading Caused by SOC Imbalance in Lithium-ion Batteries Based on Side Reaction Currents”, by Prof. Kingo Ariyoshi. Gaining deeper understanding of the failure mechanism of lithium-ion batteries (LIBs) is particularly important to further extend the lifetime of LIBs. This paper systematically demonstrates that the state-of-charge (SOC) imbalance between the positive and negative electrodes is the primary cause of capacity fading in lithium-ion batteries (LIBs). The imbalanced SOC is quantitatively described by the difference in inter-electrode side reaction current (ISR) between the electrodes. The author also indicates that side reactions can be classified into material-intrinsic reactions and additional reactions, such as crosstalk reactions, and that each can be quantified experimentally using symmetric cells and other methods. The mechanistic insights on degradation mechanisms and analytical techniques for the critical indicator (ISR) of the lifetime will contribute to establishing rational strategies in designing high-performant long-lifetime LIBs.

“Generation and Reaction of Benzyl Triflates by Anodic Oxidation of Toluenes” by Dr. Yosuke Ashikari et al. is selected as an Editor’s Choice. This study presents a highly original electrochemical strategy that enables the selective generation and utilization of benzyl triflates via the anodic two-electron oxidation of toluenes. By conducting the oxidation at −78 °C in a divided H-type cell, the authors successfully accumulated benzyl triflates as stable benzyl-cation equivalents, a species directly confirmed for the first time by low-temperature NMR analysis. Subsequent reactions with alcohols, thiols, and amines proceeded smoothly to afford benzylic ethers and thioethers under mild, activator-free conditions, effectively suppressing the overoxidation issues inherent to conventional benzylic C–H functionalization.This work offers a valuable and innovative platform for C–H bond functionalization using electrochemically generated cationic intermediates.

“Development and Demonstration of Large-scale Alkaline Water Electrolysis System ‘Aqualyzer’” by Yasuhiro Fujita et al. is selected as an Editor’s Choice. The paper presents an outstanding achievement in developing and demonstrating the large-scale alkaline water electrolysis system. Building on the company’s long-standing expertise in chlor-alkali electrolysis, the authors establish an integrated system that combines advanced cell components with sophisticated control and simulation technologies. The cover photograph features the newly constructed alkaline water electrolysis pilot test plant at Asahi Kasei’s Kawasaki Works, supported by the NEDO “Green Innovation Fund” adopted in 2021, and in operation since May 2024. Together with the 10 MW-class system at the Fukushima Hydrogen Energy Research Field (FH2R), these developments demonstrate remarkable technological maturity and industrial readiness. Furthermore, the integration of dynamic pressure control, reverse-current suppression, and simulation-based optimization for hydrogen-cost reduction exemplifies a comprehensive engineering approach that bridges materials science and system design. This paper highlights Japan’s leading contribution to the global green-hydrogen initiative and serves as an excellent reference for the future realization of 100 MW-class electrolysis plants and a sustainable hydrogen economy.

“Development of Photocatalysts for Artificial Photosynthesis Aiming at Carbon Neutrality” by Professor Akihiko Kudo is selected as an Editor’s Choice as commemorated for the Society Award of Electrochemical Society of Japan (Takei Award). The authors liken chess pieces to the roles of photoelectrochemical catalysts. The three chess pieces hint at different “winning lines”: a straight thrust, a leap, and long-range coordination suggesting suitable crystal engineering for development of photocatalysts and photoelectrochemical cells with band engineering. In this light, they point to two strands of the work. One concerns material systems that combine visible-range absorption with efficient hole transport by creating a “new valence band,” exemplified by BiVO4 (Bi 6s) and SnNb2O6 (Sn 5s). The other concerns design approaches that steer photoexcited carriers in one direction through cascaded band alignment, including Z-scheme architectures such as the (CuGa)0.5ZnS2–BiVO4 couple for CO2 reduction with O2 evolution. Taken together, these motifs may be read as evoking a variety of “moves”: robust performance in single-phase materials and defect/doping control; the opening of new pathways through valence-band re-design; and, further, cascaded band alignment realized through solid solutions, heterojunctions, and electron mediators.