Solar-driven hydrogen production technologies are of increasing interest. In this work, Ti3+ was incorporated into titanium dioxide via wet bead-milling, resulting in enhanced photocatalytic activity under both UV and visible light irradiation. The broad optical absorption obtained from the presence of Ti3+ ranged from the visible to near-infrared regions of the spectrum (specifically from 400 to over 900 nm) and this absorption could be enhanced by increasing the diameter of the beads used for wet milling. The hydrogen production rate from water in response to ultraviolet (UV)-visible light with ethanol as a sacrificial reagent was also found to vary depending on the bead diameter. Producing the optimal level of Ti3+ incorporation in the titanium oxide matrix while maintaining a high specific surface area increased the extent of hydrogen production during water decomposition. A sample prepared using 0.3 mm diameter beads exhibited the highest hydrogen production rate of 145 μmol h-1 g-1, which was 15 times that obtained from commercially available anatase-type titanium dioxide having higher specific surface area. The hydrogen production rate under only UV light (< 400 nm) was decreased to one-ninth of that obtained using both UV and visible light simultaneously. No hydrogen gas was generated in trials using only visible light (> 410 nm). These results indicate that visible light significantly promoted the photocatalytic reaction when both UV and visible light were irradiated simultaneously.

Cu quantum-dots of ∼1 nm having large band gaps were produced in porous silicas and size-dependent band-edge shifts were experimentally characterized.

Layered double hydroxides (LDH) were synthesized from zinc-plating wastewater and its applicability to boron adsorbent was investigated. Since the high concentration of sulfate ions in zinc-plating wastewater is assumed to inhibit the boron adsorption capacity, we searched for optimal synthesis conditions using simulated wastewater with sulfate ions added. It was suggested that the boron adsorption capacity of LDH decreases when large amounts of sulfate ions are present in wastewater. However, in case carbonated-LDH was synthesized with sodium carbonate and the interlayer carbonate ions were removed by calcination at 450 degrees C, oxidized LDH (LDO) was obtained, and the amount of sulfate ion contained in LDO was reduced, thereby boron adsorption capacity was improved. LDO obtained by calcination at 450 degrees C had the same boron adsorption capacity as that of the simulated wastewater, even when using zinc-plating wastewater, so the influence of foreign substances other than sulfate ions was negligible. Therefore, this study is expected to be an effective method of utilizing zinc-plating wastewater.

Composites of zeolitic imidazolate framework-8 (ZIF-8) and biomolecules have garnered much attention because the environmental tolerance of biomolecules is enhanced in the composites with ZIF-8. Those composites are formed easily by dissolving biomolecules with precursors of ZIF-8 in an aqueous solution. However, correlation between the composites' properties and forming conditions remains unclear. In this study, we specifically examined composites of ZIF-8 and an enzyme (glucose oxidase): a much-researched composite for application purposes. For such composites, the crystallite size dependence of ZIF-8 on prepared molar ratio of precursors (2methyimidazole / Zn ion, i.e., Hmim/Zn) was assessed and compared to that found in an earlier study for pure ZIF-8 without seeding. Results show that the ZIF-8 crystallite size decreased along with the decrease of the molar ratio of precursors. This correlation is opposite to that in cases of pure ZIF-8. Thus, the formation process of ZIF-8 in presence of enzyme is supposed to be much different from that of pure ZIF-8, and such process was discussed focusing on the pH-dependent coordination state of Zn ion in preformed amorphous phase of composite. Furthermore, the molar ratio of precursors affected the enzyme immobilization efficiency. Along with molar ratio of precursors, variations of counter anion of Zn were also investigated and discussed.

A combined solvothermal method and post-annealing to synthesize highly active ZnS-ZnO nanosheets is presented. ZnO was produced on ZnS nanosheets by thermal annealing ZnS/ethylenediamine in air. From combined studies of experimental and computational works, we revealed that during annealing, carbon (C) element was a major dopant from the decomposition of ethylenediamine, which was unintentionally doped into the ZnS-ZnO, and gave major impacts on enhanced visible-light photocatalysis. Rhodium (Rh) was deposited by in situ photoreduction to form a ZnS-ZnO/Rh catalyst composite. This multijunctioned photocatalyst was outstanding for H-2 generation from pure water under solar simulating light due to effective charge separation by Z-scheme heterojunction of ZnS and ZnO and Schottky junction of Rh-cocatalysts/semiconductors. This facile method realizes multijunctioned ZnS-ZnO/Rh photocatalysts with substantial defects that are very promising for solar energy harvesting applications.

All-solid-state Z-scheme photocatalysts, containing Cu2O, TiO2 (rutile), and Au as the electron mediator, were prepared and applied to the reduction of Cr(VI) in aqueous solutions. The Cu2O-Au-TiO2 composites were prepared by loading Au core-Cu2O shell hemisphere particles on TiO2 (rutile) nanorods using a two-step photocatalytic deposition process. Under ultraviolet-visible (UV-vis) light illumination, the Cu2O-Au-TiO2 composites exhibited higher photocatalytic Cr(VI) reduction activities than those exhibited by single TiO2 (rutile) and Cu2O. In this reaction, a precipitate containing Cr, which was considered to be Cr(OH)3, was deposited site-selectively on the Au core-Cu2O shell particles of the composites, indicating that the reduction site of the composite was Cu2O, and the reaction proceeded according to the Z-scheme. The Cu2O-Au-TiO2 composites also exhibited photocatalytic activity under visible light illumination. The oxidation state of Cu in the Cu2O-Au-TiO2 composite gradually changed from Cu(I) to Cu(II) during the photocatalytic Cr(VI) reduction. However the composite maintained its high photocatalytic performance even after oxidation. The role of Au in the Cu2O-Au-TiO2 composite was examined by comparing the properties of the Cu2O-Au-TiO2 composite with those of the Cu2O-TiO2 composite prepared via direct Cu2O deposition on TiO2.

Herein, mesoporous silica was prepared using the co-precipitation process by adding Mg, Ca, or Sr. The specific surface areas of silica were maintained with the incorporation of Mg or Ca substitutes with several tens mol%; however, they were observed to decrease significantly due to the Sr substitution. Further, the applicability of Mg, Ca, and Sr as modifiers was estimated using XPS spectra. The simultaneous ion-exchange in the mesoporous silica hybrids was confirmed by testing an aqueous solutions containing 12 coexisting rare earth metal cations. A higher degree of adsorption was obtained as the ionic radius of the cations decreased. In addition, the concave tetrad effect demonstrated that adsorption occurred through the ion-exchange reaction at specific active sites. To investigate the kinetics of the ion-exchange reaction, rate constants were estimated from time-dependency measurements. The measured rate constants for the hybrids were approximately 5.4×10-3, 5.2×10-3, and 1.5×10-3 min−1, for Mg, Ca, and Sr, respectively. Silica hybrids containing Mg and Ca exhibited mesoporous structures that proved to be advantageous on accelerating the reaction rates obtained for lanthanoid adsorption.

Photocatalysts have attracted interest in the applications of green technology due to its efficiency to eliminate detrimental substances under light irradiation. Various design strategies to enhance the efficiency of photocatalytic processes under solar irradiation is actively searched. Building on the idea to provide a better synthesis method of photocatalyst, this study explores an effective and simple synthesis strategy of Layered Double Hydroxide (LDH) silver hybrid for photocatalyst phenol degradation. Unlike the common photodeposition method that incorporates noble metal nanoparticle on the LDH surface, this study discovered a pathway of intercalation of Ag nanoparticle into LDH interlayer space by exfoliation route. Notably, the synthesized ZnAl LDH/Ag contents of several phases: Zn2.5Al(OH)(6.5)O-0.5(DS)(0)Ag-.5(0).3, Zn2.5Al(OH)(7) (HDS)(0.5)(DS)(1.5), Zn2.5Al(OH)(6)O-.3(2)0(.6)8(CO3)(0)Ag-.1(6)0.03, Zn2Al(OH)(5.32)O-0.68(CO3)(0.16). A preliminary demonstration of the concept was given by the efficient photocatalytic degradation of phenol with a resulting conversion ratio of phenol under light (Xe lamp, > 340-nm cut-off filter) irradiation by 80 % in 210 min. These findings provide a new strategy to incorporate noble metal nanoparticles into LDH interlayer space as a great potential for photocatalyst.

Layered calcium niobate perovskite with partial substitution of Nb by Ru was prepared for the catalyst of H-2 generation from NH3. The X-ray photoelectron spectroscopy confirmed that the substituted Ru exists at the intralayer position. The layered perovskite was exfoliated and re-aggregated with Ru and Na cation to increase the surface area to form a card house-type porous hybrid. The surface area apparently increased to around 12-18 times compared to the sample without exfoliation. The amount of interlayer Ru is much larger than that of the intralayer Ru from the X-ray fluorescence measurement. From the H-2 generation measurements, different roles of the intralayer and interlayer Ru were considered as follows. The interlayer Ru lowers the starting temperature of the H-2 generation, whereas the intralayer Ru increase the H-2 generation rate. (C) 2020 The Ceramic Society of Japan. All rights reserved.

Pyrochlore-type silver tantalate, Ag0.93TaO2.97·0.94H2O (AT), and fluorite-type silver niobate Ag0.41Nb0.59O1.68 (AN), were prepared by ion-exchange reactions and their ion conductivities were measured from 25 to 240°C. The total conductivities (ionic + electrical) at 240°C of AT and AN reached 4.00 © 1013 and 9.03 © 1014 S/cm, respectively. The activation energy of AT was 0.61 eV and AN showed non-linear behavior with activation energies of 0.52 eV at temperatures less than 120°C and 0.33 eV at temperatures greater than 120°C. The crystal structures of AT and AN were maintained from 25 to 240°C. ©2020 The Ceramic Society of Japan. All rights reserved.

In this work, rutile, anatase, and SrTiO3-TiO2 composites were prepared by acid treatment of SzTiO(3) using various concentrations of HNO3 at 90 degrees C. The product of the acid treatment depended on the acid concentration: fine TiO2 (anatase) particles were obtained for 0.5 M, a mixture of anatase- and rutile-phase TiO2 was obtained for 1 M, and large dumbbell-like TiO2 (rutile) particles were obtained for 2, 3, and 4 M HNO3. Furthermore, SrTiO3-TiO2 (anatase) composites in which fine TiO2 (anatase) particles formed on SrTiO3 cores were produced by a short-duration acid treatment. The composite exhibited a higher photocatalytic activity than the SrTiO3, TiO2 (anatase), TiO2 (rutile), and mixture of anatase- and rutile-phase TiO2 in methylene blue decomposition. The hybridization of SrTiO3 and anatase with a large contact area was considered to prevent rapid electron-hole charge recombination and to enhance the photocatalytic activity of the composites.

Four types of bismuth oxides, Na3Bi3O8, NaBiO3, α-Bi2O3, and ε-Bi2O3, were obtained by hydrothermal reactions using NaBiO3·nH2O in NaOH solution. The crystal structure of a new phase (Na3 Bi3+)Bi25+O8 ((Na0.75Bi0.25)2BiO4) was determined by using single crystal X-ray diffraction data, and this compound was found to show a Na2MnCl4-related structure with a monoclinic system (space group, Pm) with the following lattice parameters: a = 5.990 (2) Å, b = 3.335 (2) Å, c = 10.108 (2) Å, and β = 91.08 (3)°. The final R-factors R1 and wR2 were 0.041 and 0.090 (all data), respectively. The new phase was composed of mixed valence states of Bi (Bi3+ and Bi5+, with a mean Bi valence of 4.30) with five distinct Bi sites, where two Bi5+ (Bi1 and Bi2) fully occupied the distorted octahedral sites and three Bi3+ (Bi3, Bi4, and Bi5) were statistically distributed at the split sites with Na+ (Na3, Na4, and Na5). The Na6 site is fully occupied. The distorted Bi5+O6 octahedra formed one-dimensional chains via edge-sharing along the b-axis, with the chains held by Bi3+/Na+ split sites. The structural feature except for the split distribution of Bi3+/Na+ was classified as a Na2MnCl4-type structure. DFT calculations based on a model discounting the split distribution of Bi3+/Na+ indicated that Bi 6s and O 2p orbitals form sp hybridization at the conduction band. This new mixed valence bismuth oxide exhibited photocatalytic activity for phenol degradation under visible light irradiation. In addition to Na3Bi3O8, the hydrothermal reaction using NaBiO3·nH2O in NaOH solution yielded micrometer-sized single crystals of an ilmenite-type NaBiO3 and two polymorphs of bismuth oxides with monoclinic (α-Bi2O3) and orthorhombic (ε-Bi2O3) structures, depending on the reaction temperature and NaOH concentration.

A pyrochlore-type strontium bismuthate, (Sr0.75Bi0.25)(2)Bi2O6.83 was synthesized by a hydrothermal method using NaBiO3 center dot nH(2)O as a starting material. The crystal structure was refined using synchrotron powder X-ray diffraction data. The final R-factors were R-wp = 8.07 % and R-p = 5.87 %, and the lattice parameter was a = 11.0195 (2) angstrom. This compound had a mixed bismuth valence state involving Bi3+ and Bi5+, where Bi3+ partially occupied the A-site (Sr2+) as well as the B-site (Bi5+) in the pyrochlore-type structure. Moreover, the present compound was found to be a diamagnetic semiconductor with electrical resistivity of similar to 90 Omega m at room temperature. (C) 2020 The Ceramic Society of Japan. All rights reserved.

Electrodes with nanosheet architectures can offer the possibility to achieve enhanced energy storage performance. Herein, we have designed and synthesized novel nanosheet structures of CoAl layered double hydroxide (LDH)-polyaniline (PANI) nanocomposite thin films by a hydrothermal-electrodeposition method. The molecular structure, crystal structure, morphology and chemical composition of the composites were characterized by FT-IR, XRD (SXRD), FESEM, and XPS, whereas their electrochemical properties were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. Compared with the unmodified CoAl LDH, the CoAl LDH-PANI exhibits significantly improved the specific capacitance and cyclic stability. The composite exhibits a high specific capacitance of 528 F/g at a current density of 10 A/g and excellent cyclic stability with an increase of the specific capacitance of 42.7% after 6000 cycle tests. We revealed the degradation behavior of PANI in 1 M KOH/KCl electrolyte, and the active degradation products also further increased the total specific capacitance of the composite. The enhanced electrochemical performance of the nanocomposite can be attributed to its well-designed nanostructure and the synergistic effects of each component. By analyzing the band structure and density of states of CoAl LDH and PANI, we proposed the possible mechanism of synergistic effect in a new perspective.