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Millimeter-sized K2Ti2O5 single crystals were grown from a KCl–KOH mixed flux using a flux-evaporation assisted method. H2O was found to be the best solvent for the liquid exfoliation of K2Ti2O5 crystals.

In order to tailor the morphology of the layered double hydroxide (LDHs) particles, we focused on a synthesis method that involves the use of Al2O3 as a precursor, employing Al2O3 with different crystal structures (e.g., α-Al2O3, θ-Al2O3, and γ-Al2O3) as well as amorphous Al2O3. A three-dimensional network of plate-shaped LDH particles was formed when θ-Al2O3 and γ-Al2O3 were used, even though α-Al2O3 barely reacts to form the LDH phase. Finally, adsorption tests involving HPO42− ions confirmed that the fabricated LDH particles exhibited high ion-removal rates. The LDH particles prepared with θ-Al2O3 and γ-Al2O3 could remove the hydrogen phosphate ions (HPO42−) in a concentration of 0.40 mmol g−1 completely within 10 min; this is approximately 20 times shorter than the time taken by the LDH particles prepared from amorphous Al2O3.

The controlled growth of needle-shaped and planar bar-shaped NaFeTiO4 crystals, a CaFe2O4-type structure, was carried out by a flux method using a NaCl–Na2SO4 binary flux. NaCl fluxes have been empirically investigated for growing unique anisotropic crystal shapes. However, strategies for controlling the crystal morphology based on NaCl fluxes have not been established. In this study, Na2SO4 was added to a NaCl flux to supply O2− ions, which is essential for the dissolving ability of a metal oxide into ions, and the growth manner was systematically investigated as a function of flux composition. As a result, needle-shaped crystals were obtained from the pure NaCl flux with exposed {100} facets. Meanwhile, with the binary flux, the morphology of the crystals changed from a needle shape to a planar bar shape depending on the Na2SO4 content, where the aspect ratio of the {100} facets was increased by about ten times. It was found out that the aspect ratio of the {100} planes of NaFeTiO4 crystals can be controlled kinetically by the cooperative effect of Na+ ions and anionic species in the flux; Na+ ions stabilize the {100} facets and a high O2−/Cl− ratio increases the concentration of ions as a precursor for crystal growth to promote the growth in the direction, resulting in planar bar-shaped crystals. We believe that the morphological control regime demonstrated here in the growth of NaFeTiO4 crystals in a NaCl–Na2SO4 binary flux could be a useful idea in high temperature chemistry and for their desirable applications.

Cu–In–Ga–S–Se (CIGSSe) is a promising light-absorber in thin-film photovoltaic cells, as well as a photocathode for solar H2 production, but the fabrication of layers of CIGSSe crystals on substrates is both time- and cost-intensive. Here, we report the fabrication of CuInS2 crystal layers on various precursor-loaded Mo/soda-lime glass (SLG) substrates using a flux coating method. X-ray diffraction analysis indicated that the main phase was CuInS2, while MoS2 which formed through the sulfurization of the Mo substrate was present as a minor phase. Top-surface field-emission scanning electron microscopy (FE-SEM) images indicated that the CuInS2 crystals were sparsely formed on the bare Mo/SLG, In/Mo/SLG, and Cu/Mo/SLG substrates. In contrast, closely packed CuInS2 crystals were formed on Cu2S/Mo/SLG. Smaller CuInS2 crystals 0.5–1 μm in size were grown on Cu2S/Mo/SLG compared to those on other substrates. This sharp difference in crystal population and size could be attributed to the pre-loading effect of the precursors. Cross-sectional FE-SEM analysis with energy-dispersive X-ray spectroscopy mapping revealed the homogenous fabrication of idiomorphic CuInS2 crystals on the partially sulfurized Mo substrate, yielding a CuInS2/MoS2/Mo heterostructure amenable to photovoltaic applications. The formation mechanism of this unique heterostructure was discussed based on the experimental results.

The use of ammonia as a hydrogen carrier has received much attention due to its high hydrogen content and liquid state under mild conditions, which could lead to fuel cell applications. This study demonstrates facile ammonia decomposition on ruthenium nanoparticles loaded on inorganic electride, C12A7:e−. A high turnover frequency (∼12 s−1 at 400 °C) and low activation energy (64 kJ mol−1) for recombinative N2 desorption were obtained for Ru/C12A7:e−. N2-temperature programmed desorption (N2-TPD) and kinetic analyses indicate that the high catalytic performance is due to the low work function of chemically stable C12A7:e−, which enables electron injection to the antibonding orbital of the Ru–N bond formed transiently through the reaction by raising the Fermi level of Ru metal.