Takayuki Homma

The behavior of bubbles generated by the hydrogen evolution reaction (HER) and the effect of these bubbles on HER performance were investigated using Ni micro-patterned electrodes. This study focused on the correlation between bubble behaviors affecting potential increase of HER and the surface microstructures of micro-patterned Ni cathode. Ni microdot array structures with diameters of approximately 5–10 μm, pitch of approximately 5–10 μm, and various dot heights were fabricated for alkaline wa

Electrochemical processing can potentially be used for the cost-effective and large-scale fabrication of solar cells based on nanostructured Si thin films. Herein, we fabricated Si thin films for solar cell applications by electrodeposition in ionic liquids and performed a systematic investigation of film structure control and doping effects. Notably, relatively smooth and compact films were obtained by the modulation of the rest time during the electrodeposition under light irradiation, and the

Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid–liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extra

Abstract We designed an in situ surface‐enhanced Raman spectroscopy (SERS) system to detect pH change near the electrode surface. An optically transparent substrate covered with Ag nanoparticles (NPs) that induce SERS was positioned vertically to the electrode. A probe molecule that protonates/deprotonates according to the change in pH of surroundings were distributed nearby the NPs, so that the SERS spectrum of the probe indicated the pH changes in the vertical direction to the electrode due to

Electroless deposition enables the in situ growth of NiFeP electrocatalysts on anion exchange membrane, resulting in a binder- and ionomer-free structure that enhances the catalytic activity and durability to hydrogen evolution reaction.

Water-repellent glass surfaces have become increasingly important to ensure clear visibility in outdoor cameras, sensors, and automotive windows. In this study, we investigated a process for the formation of nanoscale structures on a glass surface using chemical reactions with hydrogen fluoride gas. Using this approach, nanostructures with superhydrophobicity, superhydrophilicity, and antireflective properties were formed on glass surfaces with minimal processing time. This mask-free method, wor

Zn negative electrodes are expected to be used in next-generation batteries. However, irregular shape evolution, such as mossy structures, limits its practical applications. Cationic additive species are useful in suppressing this, and Li + is a promising species. To identify the effect of Li + on the nucleation and growth of Zn, this study analyzed the Zn aggregation behavior during electrodeposition with Li + at the initial stage via experimental methods and theoretical calculations using dens

Zn is a promising anode material for next-generation large-scale energy storage devices. However, irregular shape evolution on its surface during cycling causes electrode degradation. The shapes and crystal structures of the deposits naturally originate from the initial behaviors of the depositions. At the initial stage of deposition, a micro-protrusion initiates on the Zn electrode, leading to an irregular shape evolution. This study focuses on the initial steps of Zn deposition using a multisc

In this study, ultrathin CoPt alloy films oriented along face-centered cubic (fcc) (111) with perpendicular magnetic anisotropy (PMA) are fabricated by electrodeposition at room temperature and normal pressure without annealing. By increasing the concentration of Pt ions in the electrolytes, initial nucleation of CoPt becomes fine, forming epitaxial CoPt alloy films oriented along fcc (111) to the film planes with very smooth surfaces (Arithmetic average roughness Ra ∼ 0.43 nm). The deposited Co

This study directly monitored molecular structures of lubricant species during sliding using in-situ surface-enhanced Raman spectroscopy (SERS) with plasmonic sensors developed by our research group. This method, characterized by exceptional sensitivity to interfacial chemical structures and high temporal resolution (1 s), facilitated tracking changes in lubricant species. Results for pure dodecane, used as the base oil for the lubricant, revealed immediate degradation upon sliding, forming amor

In this study, ZnO formation during the dissolution−passivation process of Zn anodes is observed via in situ Raman and optical characterization. The Zn passivation during galvanostatic anodization merely follows the dissolution−precipitation model, whereas that of potentiodynamic polarization exhibits different behaviors in different potential ranges. Initially, the Zn electrode is gradually covered by a ZnO precipitation film and then undergoes solid‐state oxidation at ~255 mV. The starting poi

We demonstrate an electrochemical deposition process suitable to form arrays of L10 Fe–Pt nanodots with hard magnetic properties via electron-beam lithography, template deposition, and thermal annealing. Synthesis parameters are selected by growing single and multilayer blanket films and investigating the effect of thermal annealing on the various films. We find that the fastest ordering transformation is achieved in eight-layer Fe–Pt multilayers with a sublayer thickness of 2.5 nm, while a sing

Thick copper selenide (Cu₂Se) films were synthesized potentiostatically in acidic aqueous solutions, demonstrating a controlled and scalable pathway for fabricating high-performance microdevices. The study systematically examined the influence of solution composition and pH on film morphology, revealing that pH is critical in achieving compact, nonporous, and smooth-surfaced films. For the first time, scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed the d