Orbital Engineering in Sillén–Aurivillius Phase Bismuth Oxyiodide Photocatalysts through Interlayer Interactions

Multicomponent inorganic compounds containing post-transition-metal cations such as Sn, Pb, and Bi are a promising class of photocatalysts, but their structure–property relationships remain difficult to decipher. Here, we report three novel bismuth-based layered oxyiodides, the Sillén–Aurivillius phase Bi₄NbO₈I, Bi₅BaTi₃O₁₄I, and Bi₆NbWO₁₄I. We show that the interlayer Bi–Bi interaction is a key to controlling the electronic structure. The replacement of the halide layer from Cl to I negatively shifts not only the valence band but also the conduction band, thus providing lower electron affinity without sacrificing photoabsorption. The suppressed interlayer chemical interaction between the 6p orbitals of the Bi lone-pair cations reduces the conduction bandwidth. These oxyiodides have narrower band gaps and show much higher water oxidation activities under visible light than their chloride counterparts. The design strategy has not only provided three novel Bi-based photocatalysts for water splitting but also offers a pathway to control the optoelectronic properties of a wider class of lone-pair (ns²np⁰) semiconductors

Isotopic fractionation of water during snow formation: Experimental evidence of kinetic effect

Deuterium excess(d-excess=δD-8・δ^(18)O), which is calculated using two water isotope ratios(δD and δ^(18)O), is an indicator of kinetic isotope fractionation. The d-excess value reflects the evaporation process from the ocean or ice-crystal growth. Consequently, d-excess records preserved in ice cores may provide a climatic history of ocean surface conditions at the vapor source area. J. Jouzel and L. Merlivat(J. Geophys. Res., 89, 11749, 1984) proposed an isotope model to analyze information from ice cores. That model includes kinetic fractionation during snow formation, depending on the degree of the supersaturation ratio of vapor. However, no experiment was conducted under the controlled supersaturation ratio. Experiments described herein measured the isotopic ratios of the vapor and artificial snow produced under a controlled supersaturation ratio to confirm the kinetic isotope effect experimentally. Results indicate a higher d-excess value for ice crystals at a higher vapor supersaturation ratio and provide experimental evidence for the kinetic effect during snow formation

An unexplored role of the CrOx shell in an elaborated Rh/CrOx core–shell cocatalyst for photocatalytic water splitting: a selective electron transport pathway from semiconductors to core metals, boosting charge separation and H₂ evolution

A core–shell structured Rh/CrOx cocatalyst has endowed various semiconductors with high efficiency in water-splitting photocatalysis, where thin CrOx layers on Rh have been assumed to be physical blockers of O₂ to the metal surface to suppress unfavorable reverse reactions (e.g., catalytic H₂O formation from H₂ and O₂). Herein, we propose another unexplored but favorable function of CrOx layers: a selective electron transport pathway from photocatalysts to the Rh core boosting charge separation and H₂ production. The subsequent loading of CrOx layers onto Rh increased the rate of visible light H₂ evolution of a Bi₄NbO₈Cl photocatalyst, even in a half reaction with a hole scavenger where O₂ does not evolve. Transient absorption spectroscopy revealed that the CrOx layer increases the electron path from Bi₄NbO₈Cl to Rh. Importantly, the highest H₂-evolution activity was obtained by simultaneous photodeposition using CrIII and RhIII precursors, which had not yet been examined. In this sample, Rh nanoparticles were enclosed by an amorphous CrOx shell, where Rh particles were less directly attached to the semiconductor. Therein, CrOx inserted between Bi₄NbO₈Cl and Rh effectively suppresses undesirable hole transfer from Bi₄NbO₈Cl to Rh, while such hole transfer partially occurs when they are in direct contact. These results indicated that CrOx functions as a selective electron transport pathway and improves the H₂ evolution activity. Although the development strategy of cocatalysts has so far focused on surface redox reactions, this study offers a new approach for the design of highly efficient cocatalysts based on the carrier transfer process, especially at semiconductor–cocatalyst interfaces

Surface Modification with Metal Hexacyanoferrates for Expanding the Choice of H₂-Evolving Photocatalysts for Both Fe³⁺/Fe²⁺ Redox-Mediated and Interparticle Z-Scheme Water-Splitting Systems

The construction of Z-scheme water splitting systems is an effective approach toward harvesting a wide portion of the solar light spectrum; however, the success has often depended on the property of photocatalyst surfaces. This drawback is typified by the limited choice of efficient H₂ evolution photocatalysts (HEPs) (e.g., Rh-doped SrTiO₃) for Z-scheme water splitting using Fe³⁺/Fe²⁺ redox couple. The majority of visible light-responsive materials shows low activity for H2 production with Fe²⁺ electron donors despite having suitable band levels, probably due to the absence of an effective surface site for oxidizing Fe²⁺. The choice of HEPs for interparticle Z-scheme systems has also been limited. Herein, an effective strategy for overcoming these limitations is reported: activation of originally inactive materials via surface modification with metal hexacyanoferrate nanoparticles. Photocatalytic H2 evolution over TaON in aqueous Fe²⁺ solution is drastically enhanced by comodification with indium hexacyanoferrate (InHCF) and Rh–Cr mixed oxide. InHCF promotes Fe²⁺ oxidation to Fe³⁺ utilizing the holes photogenerated in TaON via FeIII/FeII redox cycles, enabling Z-scheme water splitting with the Fe³⁺/Fe²⁺ redox mediator coupled with an O2 evolution photocatalyst under visible light. It is also disclosed that InHCF nanoparticles function as effective solid electron mediators for achieving interparticle Z-scheme water splitting

Initial Results for Science Instruments Onboard EQUULEUS During the Cruising Phase Toward the Earth Moon Lagrange Point

EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) is a spacecraft to explore the cis-lunar region including the Earth-Moon Lagrange point L2 (EML2). The spacecraft is being jointly developed by JAXA, the University of Tokyo, and several other universities in Japan. After being launched into a lunar transfer orbit by NASA\u27s SLS (Space Launch System) Artemis-1 on November 16, 2022, the spacecraft successfully performed a first Delta-V and a trajectory correction maneuver. This enabled a precise lunar flyby and successful insertion into the orbit toward EML2. Although the size of EQUULEUS is only 6U CubeSat, the spacecraft carries three different science instruments. The spacecraft can effectively demonstrate science missions during and after the flight to EML2 by using these instruments; the plasmasphere observation around the Earth by PHOENIX, the space dust flux detection in the cis-lunar region by CLOTH, and the lunar impact flash (LIF) observation at the far side of the moon by DELPHINUS. All instruments have already completed its checkout. During the cruising phase, PHOENIX conducted Earth observations and successfully identified the Earth\u27s plasmashere. CLOTH has started regular standby operations. DELPHINUS obtained impressive images such as the far side of the Moon at lunar closest approach and long-period comet, Comet ZTF. This poster presents the details of these scientific missions and the initial checkout and observation results of the science instruments

Fabrication of a porous ZnRh2O4 photocathode for photoelectrochemical water splitting under visible light irradiation and a significant effect of surface modification by ZnO necking treatment

A porous ZnRh2O4 electrode was fabricated by an electrophoretic deposition method on a fluorine-doped tin oxide substrate, and photoelectrochemical water splitting under visible light irradiation (λ > 420 nm) was performed. The porous ZnRh2O4 electrode exhibited a cathodic photocurrent under visible light irradiation and an extremely positive onset potential at +1.2 V vs. reversible hydrogen electrode (RHE) in aqueous Na2SO4 solution. ZnO necking treatment, by which effective contact between ZnRh2O4 particles is formed, afforded a significant increase in the photocurrent. The incident photon to current efficiencies (IPCEs) of the ZnRh2O4 and ZnO/ZnRh2O4 photocathodes were calculated to be ca. 8% and ca. 13% at 400 nm, respectively, at 0 V vs. RHE in aqueous Na2SO4 solution. H2 evolution under visible light (λ > 420 nm) was demonstrated using the ZnRh2O4 and ZnO/ZnRh2O4 photocathodes combined with a Pt electrode under an applied bias (0 V vs. RHE)

Climatic and atmospheric histories over the past 700,000 years from the Dome Fuji deep ice core, Antarctica

第3回極域科学シンポジウム　横断セッション「海・陸・氷床から探る後期新生代の南極寒冷圏環境変動」11月26日（月） 国立国語研究所 ２階講

Building primary care in Japan: Literature review.

Japan's health system is well known for achieving one of the world's highest life expectancy with universal health coverage. However, the country now faces challenges of a rapidly aging population and changes in patterns and burden of disease. Primary care is an important component of a well-functioning health system. In Japan, primary care services are provided in both the community and hospital settings. The distinction between primary and secondary care may not always be clear. This review is based on the framework from the 2015 WHO publication on primary care systems in Europe. Our aim is to describe the journey of primary care in Japan, with its past, present, and future as a valuable addition to the academic English literature. We also hope that this article would inspire readers outside of Japan who might face similar issues in their respective countries

A Sillén Oxyhalide SrBi₃O₄Cl₃ as a Promising Photocatalyst for Water Splitting: Impact of the Asymmetric Structure on Light Absorption and Charge Carrier Dynamics

Bismuth-based oxyhalides with layered Sillén(–Aurivillius) structures have attracted significant attention as photocatalysts. Recent studies have unveiled a part of the structure–property relationship of the materials; however, it has not been fully understood. In the present study, we investigated a Sillén-type oxyhalide SrBi₃O₄Cl₃ with single and double halogen layers. Interestingly, SrBi₃O₄Cl₃ showed a visible light response up to ∼460 nm, whereas SrBiO₂Cl and BiOCl with single and double halogen layers, respectively, did not. Rietveld refinement and STEM-EDX mapping determined the asymmetric Bi occupation in the fluorite [Sr₀.₅Bi₁.₅O₂] layer of SrBi₃O₄Cl₃, which was derived from the coexistence of the halogen layers. DFT calculations and Madelung potential calculations showed that the asymmetric Bi occupation affords both the Bi–Bi interaction across the single halogen layer and the electrostatic destabilization of Cl in the double halogen layer, probably leading to the narrow bandgap of SrBi₃O₄Cl₃. Another merit of possessing the two different halogen layers was revealed by time-resolved microwave conductivity measurements as well as DFT calculations; the spatial separation of the conduction band minimum and valence band maximum based on the coexistence of the halogen layers would promote charge carrier separation. Visible-light-driven Z-scheme water splitting was accomplished using a RuO₂-loaded SrBi₃O₄Cl₃ sample as an O₂-evolving photocatalyst. This study provides another option for engineering band structures and promoting the charge carrier separation of layered oxyhalides for efficient water splitting under visible light