Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Transparent conductors as solar energy materials: A panoramic review

The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

Over the past few decades, the design and development of advanced electrocatalysts for efficient energy conversion technologies have been subjects of extensive study. With the discovery of graphene, two-dimensional (2D) nanomaterials have emerged as some of the most promising candidates for heterogeneous electrocatalysts due to their unique physical, chemical, and electronic properties. Here, we review 2D-nanomaterial-based electrocatalysts for selected electrocatalytic processes. We first discuss the unique advances in 2D electrocatalysts based on different compositions and functions followed by specific design principles. Following this overview, we discuss various 2D electrocatalysts for electrocatalytic processes involved in the water cycle, carbon cycle, and nitrogen cycle from their fundamental conception to their functional application. We place a significant emphasis on different engineering strategies for 2D nanomaterials and the influence these strategies have on intrinsic material performance, ...

Emerging Two-Dimensional Nanomaterials for Electrocatalysis

Kamihara and coworkers' report of superconductivity at ${T}_{c}=26\text{ }\text{ }\mathrm{K}$ in fluorine-doped LaFeAsO inspired a worldwide effort to understand the nature of the superconductivity in this new class of compounds. These iron pnictide and chalcogenide (FePn/Ch) superconductors have Fe electrons at the Fermi surface, plus an unusual Fermiology that can change rapidly with doping, which lead to normal and superconducting state properties very different from those in standard electron-phonon coupled ``conventional'' superconductors. Clearly, superconductivity and magnetism or magnetic fluctuations are intimately related in the FePn/Ch, and even coexist in some. Open questions, including the superconducting nodal structure in a number of compounds, abound and are often dependent on improved sample quality for their solution. With ${T}_{c}$ values up to 56 K, the six distinct Fe-containing superconducting structures exhibit complex but often comparable behaviors. The search for correlations and explanations in this fascinating field of research would benefit from an organization of the large, seemingly disparate data set. This review provides an overview, using numerous references, with a focus on the materials and their superconductivity.

Superconductivity in iron compounds

In the recent development of the studies in iron-based superconductors, high-pressure experiments have been played an important role. Large enhancement of Tc with applying pressure and pressure-induced superconductivity were reported in LaFeAsO1-xFx. In this work, electrical, magnetic and structural measurements on 1111 type Ca(Fe1-xCox)AsF and 11 type Fe(Se1-xTex)0.92 under high pressure have been performed. For Ca(Fe1-xCox)AsF, the substitution of Co suppressed the magnetic and structural transitions and raised superconductivity. Pressure-induced superconductivity was observed for x = 0.0 and 0.05. The highest Tc was obtained in parent compound under high pressure, in contrast to LaFeAsO1-xFx. These results suggest that the substitution of Co increases carrier concentration and induces disorder in the FeAs superconducting layer. For FeTe0.92, pressure-induced superconductivity was not detected under high pressure up to 19 GPa, although the resistive anomaly due to the structural and magnetic phase transition was suppressed by applying pressure.

Pressure Studies for 1111 and 11 Type Iron-based Superconductors

The optical properties of a BaO–SnO–P2O5–B2O3 glass fiber with a very small photoelastic constant are characterized, and its phosphate and borate structure is studied via micro Raman and 31P and 11B magic-angle-spinning nuclear magnetic resonance spectrometry. The characteristics of the lead-free borophosphate fiber are equivalent to those of the developed lead silicate fiber used as an optical component in current transducers. The azimuth of polarized light is maintained through the new fiber with a very small photoelastic constant, which represents a potential new current transducer without hazardous elements. The elucidated structural units of the fiber are pyro- and metaphosphates and tetrahedral borate, which resemble the structural units of a preform glass.

Characterization and structure of a fiber of BaO–SnO–P2O5–B2O3 glass with a very small photoelastic constant

A superconductor which comprises a new compound composition substituting for perovskite copper oxides. The superconductor is characterized by comprising a compound which is represented by the chemical formula A(TM) 2 Pn 2 [wherein A is at least one member selected from the elements in Group 1, the elements in Group 2, or the elements in Group 3 (Sc, Y, and the rare-earth metal elements); TM is at least one member selected from the transition metal elements Fe, Ru, Os, Ni, Pd, or Pt; and Pn is at least one member selected from the elements in Group 15 (pnicogen elements)] and which has an infinite-layer crystal structure comprising (TM)Pn layers alternating with metal layers of the element (A).

Superconductor comprising lamellar compound and process for producing the same

The new title compound is prepared by hydrogenation of CaNiGe (obtained by arc-melting of the elements) under 2.0 MPa H2 (573 K, 40 h).

Layered Hydride CaNiGeH with a ZrCuSiAs-Type Structure: Crystal Structure, Chemical Bonding, and Magnetism Induced by Mn Doping.

Recent discoveries of topological phases realized in electronic states in solids have revealed an important role of topology, which ubiquitously appears in various materials in nature. Many well-known materials have turned out to be topological materials, and this new viewpoint of topology has opened a new horizon in material science. In this paper we find that electrides are suitable for achieving various topological phases, including topological insulating and topological semimetal phases. In the electrides, in which electrons serve as anions, the bands occupied by the anionic electrons lie near the Fermi level, because the anionic electrons are weakly bound by the lattice. This property of the electrides is favorable for achieving band inversions needed for topological phases, and thus the electrides are prone to topological phases. From such a point of view, we find many topological electrides, Y$_2$C (nodal-line semimetal (NLS)), Sc$_2$C (insulator with $\pi$ Zak phase), Sr$_2$Bi (NLS), HfBr (quantum spin Hall system), and LaBr (quantum anomalous Hall insulator), by using ab initio calculation. The close relationship between the electrides and the topological materials is useful in material science in both fields.

Satoru Matsuishi

Papers

Pressure Studies for 1111 and 11 Type Iron-based Superconductors

Characterization and structure of a fiber of BaO–SnO–P2O5–B2O3 glass with a very small photoelastic constant

Superconductor comprising lamellar compound and process for producing the same

Layered Hydride CaNiGeH with a ZrCuSiAs-Type Structure: Crystal Structure, Chemical Bonding, and Magnetism Induced by Mn Doping.

Electrides as a New Platform of Topological Materials