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Ethylamine-intercalated HxK2−xLaTa2O6N, further modified with a Pt cocatalyst, exhibited 60 times height photocatalytic activity for H2 evolution under visible light, as compared with the parent layered material.

Mixed-anion compounds, in which multiple anions such as O2−, N3−, and H− are contained in the same compound, have recently attracted attention. Because mixed-anion compounds have a unique crystal s...

Photoluminescent properties under different pH conditions and the effect of the photocatalysis over a Eu3+/Tb3+-TiNbO5− electrostatic self-assembly were investigated.

Graphene oxide (GO) contains various types of oxygen functional groups (e.g., C–OH, C–O–C, C=O, and O=C–OH groups), which provide superior functions such as proton conductivity, catalytic activity,...

Invited for the cover of this issue is the group of Biplab Manna at the University of Kumamoto. The image depicts various kinds of stacking between the metal-organic layers of MOFs. Read the full text of the article at 10.1002/chem.202201665.

Positive suppression of photocatalytic activity of TiO2 used for an antireflection film or UV-light protection material is required while maintaining its white color and transmittance of visible li...

Electrochemical (EC) reduction of graphene oxide (GO) serves as a green chemistry pathway to produce reduced GO (rGO). However, the mechanistic understanding of this process is still limited due to the structural complexity of GO-based materials. In the present study, we employ an inductive approach that consists of investigating the structures afforded by alternating EC reduction and oxidation steps to elucidate the electrochemical reduction reactions in aqueous solution. The initial EC reduction of chemically derived GO mainly converts epoxides (C–O–C) to COH/CH pairs. Simultaneously, carbon-centered radicals (C•) are eliminated. Subsequent EC oxidation does not result in restoration of epoxides but reverse dehydrogenation and radical formation. The second EC reduction and oxidation cycle involves reversible C–H formation coupled with radical elimination, suggesting that C• serves as an active site for the hydrogenation. As a result of this study, COH–CH is revealed as a plausible characteristic structure in electrochemically derived rGO. The reversible radical hydrogenation reaction can offer an effective route to manipulate the chemical reactivities of GO-based materials. We demonstrate that the electrons transferred by EC reduction can delocalize in the rGO to some extent, activating the pseudocapacitance that probably originates from COH.

Proton-conducting oxides have garnered much attention as electrolyte materials of electrochemical devices operating at intermediate temperatures ranging 400–700 °C. For the implementation, quantify...

YCoO3 is discussed as a novel cathode material for solid oxide fuel cells (SOFCs). One of the major issues for SOFC development is the side reactions that occur at the electrode and electrolyte interfaces. Characteristics such as the phase stability, reactivity against YSZ, electrical conductivity, and thermal expansion coefficients (TECs) of YCoO3 were investigated. YCoO3 was produced by the sol–gel method below 975 °C, and the fewest impurities were observed at a Y molar ratio of 0.96 (YCO-096). YCO-096 did not react significantly with the YSZ electrolyte when fired at 975 °C for 1 h. The main charge carrier of YCO-096 was confirmed to be electron–holes, h+, and the maximum conductivity was estimated to be 700 S cm−1 at 900 °C. The TECs of YCO-096 were in the range of 16.5–44.2 × 10−6 °C−1 from room temperature to 900 °C. The YCO-096 cathode was stable in the YSZ electrolyte SOFC. Oxygen defects formed at the surfaces of particle YCO-096 were considered to significantly improve the cathodic performance.

Electrocatalysts with metal–nitrogen–carbon (M–N–C) sites have recently attracted much attention as potential catalysts for the oxygen reduction reaction (ORR), and a hybrid of iron phthalocyanine (FePc) and reduced graphene oxide (rGO) is one of the promising candidates. Herein, a FePc/GO nanocomposite was synthesized by electrostatic deposition on the electrode. The electrochemically reduced FePc/GO nanocomposite (ER(FePc/GO)) contained Fe2+ centers in well reduced graphene sites without agglomeration. The ER(FePc/GO) exhibited high ORR activity with an ORR onset (Eonset) and half-wave potential (E1/2) of 0.97 and 0.86 V, respectively. Furthermore, the ORR activity successfully improved by adding an electrolyte such as KCl or KNO3. The small H2O2 yield of 2%, superior tolerance to methanol addition and high-durability indicate that the ER(FePc/GO) is a promising electrocatalyst. Theoretical studies, indicating that the presence of Cl− and NO3− ions lowered the conversion energy barrier, strongly supported the experimental results.

Nanosheets doped with isolated single-atom reaction sites for hydrogen evolution are a potential means of suppressing recombination during photocatalytic water splitting. Oxide nanosheets show high...

Our present work demonstrated electrochemical oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activities of ultrathin nickel cobalt hydroxide (NixCoy-OH, Ni/Co = x/y) nanosheet ...

A graphene oxide (GO) nanosheet with epoxy groups was prepared by exfoliating the graphite oxide. The free standing membrane of the GO nanosheet with epoxy groups was used for water purification, w...

Core/shell-type nanoparticles composed of GdPO4: x mol% Nd3+/calcium phosphate (CaPO) (0 ≤ x ≤ 5) were synthesized by a precipitation method, as nontoxic bio imaging phosphors that can emit near-infrared (NIR) light under NIR excitation. The GdPO4: x mol% Nd3+ core, obtained in a single-phase form of the monoclinic rare-earth orthophosphate structure, exhibited characteristic emissions attributed to the f–f transitions of Nd3+. The strongest emission peak was observed at 1061 nm under excitation at 800 nm in a sample containing 3 mol% of Nd3+. The average particle size of GdPO4: 3 mol% Nd3+ was 42 nm, indicating that nano-sized particles were successfully obtained. Although the average particle size of the core/shell-type GdPO4: 3 mol% Nd3+/CaPO nanophosphor was slightly increased to 54 nm by a second calcination in the surface coating process, the CaPO shell was well formed with a thickness of 3 nm around the GdPO4: 3 mol% Nd3+ core. With surface coating with the CaPO4 shell, the NIR emission intensity increased to 4.2 times higher than that of GdPO4: 3 mol% Nd3+. This emission intensity was significantly higher than that of indocyanine green, moreover, which is used in practice as an organic bioimaging reagent.

Preparation of highly porous MnO2 and Cr2O3 with regular structure was investigated in this study by using hard template method. Cr2O3 nanoarchitects with regular pore structure and α-MnO2 with porous nanosheet were successfully prepared. By mixing with single wall carbon nanotube (SWCNT), application of MnO2, Cr2O3 nano architects (Mn-Cr oxides supported SWCNT) was studied as active air electrode for Li-O2 battery which is now expecting as a new rechargeable battery with large capacity. It was found that the synergy effects between two mesoporous metal oxides with SWCNT resulted in excellent electrochemical properties of air electrode. Prepared Mn-Cr oxide supported SWCNT can sustain stable charge and discharge capacity up to 150 cycles with 500 mAh/g without capacity degradation indicating outstanding catalytic activity for oxygen reduction and evolution reaction (ORR/OER). Consecutive cyclic voltammetry tests also showed excellent reversibility of formation and decomposition of reaction products of Li2O2. This could be resulted from large pore volume and ordered structure of Cr2O3, MnO2/SWCNT air electrode.

We propose a single crystallization and transfer technique of organic semiconductors using a hydrogel capillary (gel capillary crystallization method). Single crystals of the C8-BTBT thienoacene-ba...

The present study demonstrated delamination of the layered silicate RUB-18 with no organo-modification of the silanol group. The obtained nanosheets showed a homogeneous thickness. A sponge-like material and a free-standing transparent, dense membrane were reconstructed using the nanosheets.

A perfectly oriented, free-standing and transparent titania nanosheet film was prepared using the spin-coating technique. The free-standing film (thickness: ∼210 nm) showed a wide band gap that corresponded to that of the monolayer nanosheet despite the stacking of hundreds of layers.

We have demonstrated a direct metallic conversion from nickel hydroxide nanosheets to nickel metal nanostructures by thermal annealing in vacuum. The metal transition of the single-layer nanosheets deposited on a Si substrate was revealed by x-ray absorption near edge structure (XANES) measurements. The XANES signal significantly changed at annealing temperatures above 250 °C. The metal transition temperature coincides with the reported temperatures at which layered nickel hydroxide nanosheets are converted to nickel oxide nanosheets by calcination in air. Auger measurements confirmed that a dissociation of oxygen from the hydroxide nanosheet induces the metallic conversion. The converted nickel metallic structures exhibit ferromagnetic behavior revealed by x-ray magnetic circular dichroism (XMCD) measurement. Atomic force microscopy measurements indicate that diffusions of nickel atoms on the substrates leads to a structural change from a 2D-like structure to a particle-like structure.

An all-solid-state supercapacitor with no boundary between the electrode/electrolyte interface is prepared using methanesulfonic acid (MSA)-intercalated graphene oxide (GO) membranes as a proton-conducting electrolyte. The electrodes (reduced GO) are formed within the surface of the solid GO electrolyte by a combination of self-reduction of the GO under UV-light illumination and electrochemical reduction. In this process, the surface of the GO film is converted to an electrode material with mixed electron/proton conduction, which results in the formation of a seamless capacitor structure. The resultant capacitor shows a large capacitance of 33.8 mF cm

The aim of this study is to examine cases in which emergency temporary housing units constructed in Japan following the 2011 Great East Japan Earthquake, and which were dismantled as of December 2016, were reused intraregionally. This study will clarify the relevant issues and lay out the prospects for subsequent reuse. Interview surveys were conducted with local governments that reused emergency temporary housing and with building contractors who undertook the construction work necessary for reuse. Eight applicable cases were used as subjects. The results indicated that changes in floor plan and specifications of foundation are issues during the reconstruction planning stage. The former are due to changes in sites and use, which affect changes in dimensions of material. The latter are caused by laws and regulations that require the use of wooden piles in the foundations of emergency temporary housing. Meanwhile, joining methods for components are an issue during the reconstruction work stage. From these results, to reuse emergency temporary housing, it is necessary to use components in circulation that are capable of accommodating changes in floor planning, and to join them with bolts, screws, or similar fasteners. Additionally, wooden piles of foundation are frequently problematic, and therefore, their use should be reconsidered. These are the issues that should be dealt with at the time of supply, so it also should be taken into consideration how to supply these components immediately after great disaster at the same time.

The hydrogen evolution reaction using semiconductor photocatalysts has been significantly improved by cocatalyst loading. However, there are still many speculations regarding the actual role of the cocatalyst. Now a photocatalytic hydrogen evolution reaction pathway is reported on a cocatalyst site using TiO2 nanosheets doped with Rh at Ti sites as one-atom cocatalysts. A hydride species adsorbed on the one-atom Rh dopant cocatalyst site was confirmed experimentally as the intermediate state for hydrogen evolution, which was consistent with the results of density functional theory (DFT) calculations. In this system, the role of the cocatalyst in photocatalytic hydrogen evolution is related to the withdrawal of photo-excited electrons and stabilization of the hydride intermediate species; the presence of oxygen vacancies induced by Rh facilitate the withdrawal of electrons and stabilization of the hydride.

Ca2-αLaαNb3-βXβO10 nanosheets ((α, β=0-0.14), X= Rh(LaRh), Mn(LaMn), Fe(LaFe), Ni(LaNi)) were synthesized by exfoliation using the surfactant aided sonication method. These nanosheets demonstrated superior photocatalytic activities for water splitting into hydrogen at room temperature. SEM-EDX images and spectra confirmed the morphology and composition of the materials where doped metal precursors inserted into the heterogeneous structure aided the photocatalytic activity.

Nitrogen doping into a metal oxide is a conventional method to prepare a visible-light-responsive photocatalyst. However, the charge imbalance that results from aliovalent anion substitution (i.e., O2–/N3– exchange) generally limits the concentration of nitrogen that can be introduced into a metal oxide, which leads to insufficient visible-light absorption capability. Here we report an effective route to synthesize nitrogen-doped metal oxide using KTiNbO5, which is a compositionally flexible layered oxide and can be exfoliated into nanoscale sheets. KTiNbO5 has a unique layered structure, in which Ti4+ and Nb5+ coexist in the same two-dimensional sheet, and controllable Ti4+/Nb5+ ratios while maintaining the original KTiNbO5-type structure. The use of a Nb-rich oxide precursor could allow for the improvement in the introduction of nitrogen compared with stoichiometric KTiNbO5 during thermal ammonolysis with ammonia gas. Reassembled KTiNbO5 nanosheets with a larger surface area were found to be more useful...

Large-capacity rechargeable batteries are becoming increasingly necessary for mobile devices, and the metal–air battery is currently the most promising for this application. Although Zn–air rechargeable batteries have a long research history, they remain far from commercialization due to their poor charge–discharge cycle life and are currently used only as primary batteries. One reason for this is the low stability of the air electrode against reversible operation. In this study, the extremely positive effects of a mesoporous nanosheet structure in La0.6Ca0.4CoO3 perovskite oxide—a non-precious metal air electrode catalyst—on the cycle life of the Zn–air battery (>1000 cycles) with a high discharge potential of 1.15 V at 50 mA cm−2 are demonstrated. The high reversibility is a result of low activity toward carbon oxidation during the charge process, which may result from the large surface area of the porous nanosheet structure and also the high stability of the perovskite phase.

Effects of nitridation condition on gallium-zinc oxynitride solid solution (GaN:ZnO) was investigated to optimize the composition of GaN:ZnO for dye-modified photocatalysts. Gallium nitride (GaN) formed from Ga 2 O 3 at 973 K, and GaN:ZnO was obtained over 1073 K under NH 3 gas flow. Nitrogen content in GaN:ZnO increased with increasing nitridation temperature and time, while zinc content decreased because of evaporation. Although UV–vis absorption spectra of GaN:ZnO powders were not significantly changed in different compositions, the water splitting activities of the dye-modified GaN:ZnO photocatalysts depended on the composition of GaN:ZnO. The highest formation rates of H 2 and O 2 were achieved by the GaN:ZnO containing 15% of zinc and 73% of nitrogen. Finally, the nitridation condition was optimized at 1123 K 15 h under NH 3 gas flow (200 ml/min) for preparation of the dye-modified GaN:ZnO powder as water splitting photocatalyst.

Due to a high surface area to volume ratio, two-dimensional nanosheets have gained interest for photo and/or electro-catalytic water splitting. In particular, experimental Rh doping of lepidocrocite TiO2 nanosheets has significantly increased catalytic activity. We use first-principles density functional theory to consider the oxygen evolution reaction (OER) on both pristine and transition metal doped systems. While the undoped TiO2 nanosheets exhibit several limitations and require high overpotentials during the water splitting reaction, selected dopants modify the binding strength of reaction intermediates and can reduce rate limiting thermodynamic barriers and theoretical required overpotentials. We present an activity volcano for these nanosheets, with the full spectrum of 3d, 4d, and 5d transition metals as candidate dopants. Subsequent photocatalytic measurements of OER activity with selected dopants are carried out to validate the predictions, and the trends are found to be consistent. These result...

To obtain a clean hydrogen production system, we have developed an inorganic-bio hybrid photocatalyst system based on the combination of anatase TiO2, methylviologen (MV) as an electron mediator, and a whole-cell biocatalyst consisting of [FeFe]-hydrogenase and maturase gene-harboring recombinant Escherichia coli; however, the apparent quantum yield at 300 nm (AQY300) for hydrogen production was low (0.3%). The system consists of a two-step reaction: (1) photocatalytic MV reduction by TiO2, and (2) hydrogen production with reduced MV using a biocatalyst. The enhancement of step 1 under biocatalyst-friendly conditions was investigated in an attempt to further improve the reaction efficiency. Among the condition tested, the use of 100 mM Tris-HCl (pH 7), 150 mM NaCl, and 5% (v/v) glycerol with P-25 TiO2 especially enhanced the step 1 reaction by a 300-fold increase in the MV reduction rate compared with previously tested reaction condition (100 mM Tris-HCl (pH 7), 150 mM NaCl, 5% (v/v) glycerol, and 100 mM ascorbate with anatase TiO2). Under the enhanced step 1 reaction, AQY300 and AQY350 for photocatalytic MV reduction reached 60.8% and 52.2%, respectively. The enhanced step 1 reaction thus significantly improved the overall photocatalytic hydrogen productivity of the hybrid system and AQY300 and AQY350 reached 26.4% and 31.2%, respectively. The inorganic-whole-cell biohybrid system can therefore provide noble metal-free, efficient, and clean hydrogen production.

In this work, the Isotope diffusion coefficient (D*) and surface exchange coefficient (k*) of Sc2O3 stabilized ZrO2 (ScSZ) series oxide, 6 mol% Sc2O3-ZrO2 (6ScSZ), 10 mol% Sc2O3-ZrO2 (10ScSZ) and 10 mol% Sc2O3- 1 mol% CeO2-ZrO2 (10Sc1CeSZ) were evaluated by using oxygen isotope exchange method. It was found that these ScSZ oxides showed a relatively higher D* value; 10Sc1CeSZ showed 1.1 × 10− 7 cm2 s− 1, 10ScSZ showed 9.3 × 10− 8 cm2 s− 1 and 6ScSZ showed 6.1 × 10− 8 cm2 s− 1 at 711 °C, respectively. In addition, its activation energy was 1.0 eV for 10Sc1CeSZ, 1.1 eV for 10ScSZ and 1.0 eV for 6ScSZ, respectively. The rapid change of D* due to the phase transition was also confirmed at around 600 °C in the case of 10ScSZ. The surface exchange coefficient (k*) of these ScSZ oxides showed a relatively high value at lower temperature. 10Sc1CeSZ showed 1.3 × 10− 8 cm s− 1 at 498 °C under lower vapor pressure of less than 20 Pa.

A 1.3 nm-thick nickel hydroxide (p-type, 0.5 nm)/titania (n-type, 0.8 nm) pn junction prepared by lamination of nanosheets improved the onset potential for photoelectrochemical oxidation and increased the photooxidation current, indicating that ultrathin pn junctions suppress the recombination of photo-generated carriers.