Mixed-anion compounds are emerging as promising oxygen electrocatalysts; however, the impact of anion-site engineering across various transition metals remains underexplored. Here, we investigate the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activities of Ruddlesden–Popper-type layered perovskite oxychlorides, Sr₂MeO₃Cl (Me = Mn, Fe, Co, and Ni), and compare them with the corresponding LaSrMeO₄ benchmark oxides. For the OER, chloride substitution universally enhanced the catalytic activity across all investigated transition metals. Density functional theory and X-ray photoelectron spectroscopy revealed that the oxygen p-band center serves as a universal OER activity descriptor, correlating strongly with surface oxygen vacancies and shifting closer to the Fermi level upon chloride incorporation. Conversely, the ORR pathway depends on the transition metal species. While the benchmark oxides predominantly proceed via a two-electron reduction of O₂, Sr₂MnO₃Cl and Sr₂CoO₃Cl oxychlorides exhibit apparent four-electron pathways. Specifically, Sr₂MnO₃Cl drives both direct four-electron and sequential (two-electron reduction followed by peroxide decomposition) pathways, whereas Sr₂CoO₃Cl exclusively utilizes the sequential pathway, facilitated by abundant oxygen vacancies. These findings establish fundamental design principles for tuning bifunctional oxygen electrocatalysis via anion-site engineering.

Ideally ordered anodic porous alumina can be obtained by anodization of an Al substrate with a regular pattern of dimples, which serve as starting points for pore formation. However, because the uniformity of the dimple shapes formed on the Al substrate affects the pore growth behavior, it is essential to form a dimple pattern with a uniform size and shape to prepare ideally ordered anodic porous alumina with a high aspect ratio. In this study, we fabricated ideally ordered anodic porous alumina with an interpore distance of 1.5 µm using dimple patterns formed on an Al surface by two different methods. Based on the 2.5 nm V⁻¹ relationship between interpore distance and voltage in anodic porous alumina, the anodization voltage was set to 600 V. Our study showed that, rather than using an array of dimples formed by mold texturing, using an array of dimples prepared by brief anodization followed by dissolution of the resulting anodic porous alumina yields anodic porous alumina with a uniform pore depth. As a result, it was observed that the uniformity of the pore depth led to improved regularity in the pore arrangement at the bottom of the anodic porous alumina.

The practical application of graphite anodes in sulfide-based all-solid-state lithium-ion batteries is hindered by their poor charging rate capability and interfacial instability caused by the reductive decomposition of solid electrolytes. To address this, we systematically investigated the impact of ultra-thin surface modifications on graphite using atomic layer deposition. Four materials with distinct electronic and lithium-ion conductivities, LiF, Al₂O₃, TiO₂, and Li₃PO₄, were deposited on graphite powder. While all the modifying materials effectively reduced the initial irreversible capacity by suppressing solid electrolyte reduction, TiO₂ and Li₃PO₄ significantly improved the charging rate capability owing to their high lithium-ion conductivities. Furthermore, extended floating tests revealed that the Li₃PO₄ modification uniquely maintained its enhanced rate capability, whereas the TiO₂-modified graphite suffered from kinetic degradation. Because Li₃PO₄ is an electronic insulator, it effectively restricts the continuous reduction of the solid electrolyte compared to TiO₂, which becomes electronically conductive upon lithiation. This study demonstrates that surface modification with a material that is simultaneously an electronic insulator and lithium-ion conductor is crucial for achieving high rate capability and interfacial durability in all-solid-state batteries.

This work demonstrated the electrooxidation of cellulose dissolved in a highly alkaline aqueous solution using Pt nanoparticle electrocatalysts prepared via an ionic liquid/metal sputtering technique. The amount of Pt nanoparticles loaded onto a carbon black support and the quantity of the resulting Pt/C applied to a glassy carbon disk electrode were optimized so as to obtain the highest anodic current. The resulting material outperformed a planar Pt disk electrode and Pt nanoparticles synthesized via a conventional wet chemical reduction method when used to promote cellulose oxidation. This increased performance is attributed to the smaller particle sizes and higher dispersibility of the Pt nanoparticles synthesized through the sputtering method, which combined to increase the electrochemically active surface area.

Electrochemical self-assembly (ESA) by electrolysis in one-pot containing inorganic and organic ingredients results in hybrid materials to exert augmented functionalities due to strong coupling between the constituents in nanoscale. We have recently discovered ESA of redox active hybrid thin films by addition of 2,5-dihydroxy terephthalic acid (DHTPA) to the bath for cathodic electrodeposition of ZnO employing oxygen reduction reaction (ORR). As the process of ESA has been examined, we have unveiled electrocatalysis of ORR by the oxidized form of DHTPA, 2,5-dicarboxy benzoquinone (DCBQ), to promote the growth of ZnO. By contrast, DHTPA is not catalytic for ORR. This “turn-on and -off” of electrocatalysis by redox between DCBQ and DHTPA have nicely explained the peculiar S-shaped I-V curve measured during the electrodeposition by potential cycling (PC method) employing a rotating disk electrode (RDE). The hybrid thin film electrode obtained by the PC method showed fast and stable redox with increased capacities in a neutral Na₂SO₄ solution, superior to those previously achieved by the materials obtained by potentiostatic electrolysis (PS method). Owing to re-construction of hybrid nanostructure during repetitive DHTPA/DCBQ redox, smooth, flat, crack-free and yet highly porous hybrid thin film can be grown thicker by the PC method, while facilitating electronic and ionic transport for the redox reaction. The redox capacity determined in the galvanostatic charging/discharging test at 10C-rate has increased 23 times (6.24 µAh cm⁻²) as compared to that of the PS sample, indicating a large room of further improvements. The process of ESA can therefore be seen as a synthetic route to obtain novel materials for energy storage, out of earth-abundant, non-toxic elements with low process energy, to be combined with extremely safe neutral aqueous electrolyte, ideally suited as ubiquitous power source to back-up wearable electronic devices.

Porosity in anodic aluminum oxide (AAO) is one of the key structural features in the research and development of AAO-based nanostructured devices. Although surface image analysis (SIA) using scanning electron microscopy is commonly used to measure porosity, it tends to underestimate this value because of inherent systematic errors and transient surface structures. In addition, the tendency of pores to adopt a tapered shape during high-throughput, high-temperature anodization requires accurate structural measurements. In this study, we derived a theoretical formula for calculating the effective surface porosity P_top. We assessed its consistency by quantitatively comparing the apparent surface porosity from SIA and the pore-bottom porosity P_bottom measured using the pore-filling method. The formula proposed in this study enables a direct comparison of P_top and P_bottom on a unified scale. This achievement contributes to the efficient fabrication of samples through high-temperature anodization and improves the structural design of AAO-based research and application devices.

The LaMgNi_3.9Co_0.1 hydrogen storage alloys were prepared by a vacuum powder sintering method, and the effects of sintering time (4–12 h) on their phase structures and electrochemical properties were systematically investigated. XRD analysis reveals that the alloys mainly consist of the Ce₂Ni₇ phase and PuNi₃ phase. With increasing sintering time, the phase evolution can be described as PuNi₃ → Ce₂Ni₇ → LaNi₅ (10 h). Electrochemical tests show that properly extending the sintering time can effectively improve the cycling stability and high-rate performance of the alloy. The alloy sintered for 10 h exhibits the optimal comprehensive electrochemical performance: C_max = 362.71 mAh g⁻¹, S₁₀₀ = 64.06 %, HRD₉₀₀ = 90.48 %. Electrochemical kinetic analysis reveals that the charge transfer rate plays a dominant role in controlling the electrochemical reaction.