Overall Water Splitting on the Transition‐Metal Oxynitride Photocatalyst LaMg1/3Ta2/3O2N over a Large Portion of the Visible‐Light Spectrum

One of the main targets of studies on water splitting photocatalysts is to develop semiconductor materials with narrower bandgaps capable of overall water splitting for efficient harvesting of solar energy. A series of transition‐metal oxynitrides, LaMg_xTa_1?xO_1+3xN_2?3x (x≥1/3), with a complex perovskite structure was reported as the first example of overall water splitting operable at up to 600 nm. The photocatalytic behavior of LaMg_1/3Ta_2/3O₂N was investigated in detail in order to optimize photocatalyst preparation and water‐splitting activity. Various attempts exploring photocatalyst preparation steps, that is, cocatalyst selection, coating material and method, and synthesis method for the oxide precursor, revealed photocatalyst structures necessary for achieving overall water splitting. Careful examination of photocatalyst preparation procedures likely enhanced the quality of the produced photocatalyst, leading to a more homogeneous coating quality and semiconductor particles with fewer defects. Thus, the photocatalytic activity for water splitting on LaMg_1/3Ta_2/3O₂N was largely enhanced.     

Understanding the Role of Gold Nanoparticles in Enhancing the Catalytic Activity of Manganese Oxides in Water Oxidation Reactions

The Earth‐abundant and inexpensive manganese oxides (MnO_x) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnO_x catalysts are still much lower than that of nanostructured IrO₂ and RuO₂ catalysts. Herein, we demonstrate that doping MnO_x polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnO_x/AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn³⁺ species, a small amount of AuNPs (<5 %) in α‐MnO₂/AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure α‐MnO₂.     

Size‐Dependence of the Activity of Gold Nanoparticle‐Loaded Titanium(IV) Oxide Plasmonic Photocatalyst for Water Oxidation

Mesoporous TiO₂ nanocrystalline film was formed on fluorine‐doped tin oxide electrode (TiO₂/FTO) and gold nanoparticles (NPs) of different sizes were loaded onto the surface with the loading amount kept constant (Au/TiO₂/FTO). Visible‐light irradiation (λ>430 nm) of the Au/TiO₂/FTO photoanode in a photoelectrochemical cell with the structure of photoanode|0.1 m NaClO4 aqueous solution|Ag/AgCl (reference electrode)|glassy carbon (cathode) leads to the oxidation of water to oxygen (O₂). We show that the visible‐light activity of the Au/TiO₂/FTO anode increases with a decrease in Au particle size (d) at 2.9≤d≤11.9 nm due to the enhancement of the charge separation and increasing photoelectrocatalytic activity.     

An Engineered Superhydrophilic/Superaerophobic Electrocatalyst Composed of the Supported CoMoSx Chalcogel for Overall Water Splitting

The development of high‐efficiency electrocatalysts for large‐scale water splitting is critical but also challenging. In this study, a hierarchical CoMoS_x chalcogel was synthesized on a nickel foam (NF) through an in situ metathesis reaction and demonstrated excellent activity and stability in the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The high catalytic activity could be ascribed to the abundant active sites/defects in the amorphous framework and promotion of activity through cobalt doping. Furthermore, the superhydrophilicity and superaerophobicity of micro‐/nanostructured CoMoS_x/NF promoted mass transfer by facilitating access of electrolytes and ensuring fast release of gas bubbles. By employing CoMoS_x/NF as bifunctional electrocatalysts, the overall water splitting device delivered a current density of 500 mA cm^?2 at a low voltage of 1.89 V and maintained its activity without decay for 100 h.     

Photophysical Properties and Photobiological Activity of the Furanochromones Visnagin and Khellin

The larger photobiological activity of visnagin (VI) versus khellin (KH) toward several living organisms, including fungi, viruses, yeasts and bacteria, induced a detailed investigation of the photophysical properties of these naturally occurring furanochromones, using laser-flash-photolysis, photoacoustic calorimetry and fluorescence (steady-state and time-resolved) techniques in solvents with different polarity and content of water, including micelles and vesicles. The results have shown that the magnitude of all the three rate constants out of S₁ (radiative, k_f; internal conversion, k_ic and intersystem crossing, k_isc) for VI and KH strongly depend on the solvent, namely on its hydrogen bonding ability and polarity. The changes of k_f and k_isc are due to the solvent-assisted mixing and/or inversion of the two first singlet excited states (¹n,π* and ¹π,π*), while k_ic increases with a decrease of the S_o–S₁ energy gap. As a consequence, the quantum yield of triplet formation (φ_T) strongly decreases from values of ?0.8 in dioxane to < 0.05 in water for both compounds. The magnitude of solvent polarity/hydrogen bonding ability required, at which the state order is inverted and φ_T starts to decrease, is greater for VI than for KH and consequently φ_T (VI) > φ_T (KH) over a broad range of water content including that appropriate to the environment of the compounds in a living system. These facts account for the larger photobiological activity of VI with respect to KH, regarding both the fungus Fusarium culmorum L. and the wild strain of Escherichia coli, studied by us.     

Interaction of Methanol Spray and Water‐Deficit Stress on Photosynthesis and Biochemical Characteristics of Phaseolus vulgaris L. cv. Sadry

This study was a factorial experiment with a completely randomized design and three replications. The four levels of methanol spraying were used. Spraying was carried out three times during the growing season at 10‐day intervals beginning at 4 weeks after sowing. The spraying of solution continued until saturation of droplets on the leaves was achieved. The levels of water‐deficit stress applied were nonstress, moderate water stress and severe water stress. The results showed that there was a significant difference (P ≤ 0.05) between the methanol and water‐deficit stress treatments for chlorophyll (Chl) a and Chl b, carotenoid, total chlorophyll, net photosynthesis (P_N), intercellular CO₂ (C_i), maximal quantum yield of photosystem II photochemistry (F_v/F_m), leaf moisture, water use efficiency and relative water content. The application of foliar methanol at all levels of water‐deficit stress significantly decreased the catalase activity of the roots. Under all levels of water‐deficit stress, the 30% (v/v) methanol treatment significantly decreased peroxidase activity in the roots over that for the control. The results suggest that foliar application of methanol can decrease the negative effects of water‐deficit stress on Phaseolus vulgaris L. cv. Sadry.     

Simple method of computing the partition coefficient

The values of log₁₀ P (partition coefficient, in octanol/water) were calculated for about 200 organic molecules of diverse structures and functionalities. The method involves a simple procedure and appears accurate enough for semiquantitative applications. Further, this method of calculating log₁₀ P values was shown to be successful in providing a better quantitative structure activity relationship (QSAR ) than the Hansch-type approach in the study of inhibitory activity of substituted phenols on Bacillus Subtilis spore germination.     

Water Activity Dependence of Lipases in Non-aqueous Biocatalysis

Eleven lipases are tested and it was found that lipases can be divided into three types according to water activity dependence. The first type is lipase that has low water activity dependence and works in a low water activity, its performance changes little with the change of water activity. The optimum water activity is 0.19 and Newlase F (Rhizopus niveus), lipase FAP-15 (Rhizopus oryzae) belong to this type. The second type is lipase that has medium water activity dependence and its performance changes with the change of water activity. Most lipases belong to this type and the optimum water activity in this type is about 0.60. The third type is lipase that has a high water activity dependence and works only in a high water activity (a _w  > 0.75). WGL (wheat germ) belongs to this type and the optimum water activity is 0.90. The relationship between enantioselectivity and water activity is also discussed and the enantioselectivity seems to be independent of water activity. And we also compared the two control methods of water activity, it was found that the method which add solid salt hydrates to the reaction mixture (method II) is more stable and effective throughout the reaction than the method that pre-equilibrate via the vapor phase (method I). The addition concentration of salt hydrates is also investigated and the optimum concentration is 1 g/l.     

A New and Sensitive Catalytic Resonance Scattering Spectral Assay for the Detection of Laccase Activity Using H2O2‐I−‐TDMAC System

In pH 3.8 acetic acid‐sodium acetate (HAC‐NaAC) buffer solution, laccase exhibited a strong catalytic effect on the H₂O₂ oxidation of I ^? to form I₂, and I₂ combined with excess I ^? to form I₃^? that reacted with cationic surfactants of tetradecyl dimethylbenzyl ammonium chloride (TDMAC) to produce the (TDMAC‐I₃)_n association complex particles, which exhibited a strong resonance scattering (RS) peak at 468 nm. Under the chosen conditions, as the concentration of laccase activity increased, the RS intensity at 468 nm (I_{468 nm}) increased linearly. The increased RS intensity ΔI_{468 nm} was linear to laccase activity in the range of 0.08–0.96 U/mL, with a regression equation of ΔI_{468 nm}?88.8U?1.9, and a detection limit of 0.02 U/mL laccase. This proposed method was applied to detect laccase activity in waste water, with satisfactory results.     

Studies of the heat of vaporization of water associated with cellulose fibers characterized by thermal analysis

The heat of vaporization (H _vap) of water associated with cellulose fibers versus moisture ratio was determined using modulated differential scanning calorimetry. A steep increase in the H _vap for decreasing moisture ratio was observed at low moisture ratios (0.0–0.3 g/g), indicating a higher energy required to evaporate water interacting with the cellulose. The water molecules with elevated H _vap correspond to non-freezing bound water. This may be attributed to (a) energy to break mono and/or multilayer sorption and (b) energy to overcome capillary forces. For polypropylene and glass fibers, H _vap was constant versus moisture ratio, in agreement with no non-freezing bound water existing in these systems. It is suggested that non-freezing bound water could be used as an indicator of H _vap, and vice versa, at low moisture ratios.     

Hydrogenation of Aromatics with [Ru(η 5-C5H5)Cl(TPPDS)2] in Biphasic Medium

[Ru(η⁵-C₅H₅)Cl(TPPDS)₂], [TPPDS=P(C₆H₅)(C₆H₄SO₃⁻)₂] in biphasic (n-heptane/water) medium hydrogenates toluene, benzene and m-xylene (105 °C, 1400 psig H₂, substrate/catalyst=600:1, 4 h) and in toluene hydrogenation gives methylcyclohexane. Catalytic activity increases with temperature, H₂ pressure, ionic strength, and pH lower than 10. The catalytic water solution can be reused several times with little activity loss.     

Hydroformylation reactions of the trans -Mo(CO)4( p -C5NH4SO3NA)2 complex in biphasic medium

Trans-bis(sodium pyridine-p-sulphonate)tetracarbonylmolybdenum(0) complex, (trans-Mo(CO)₄(p-PySO₃Na)₂, (1)) was used as a catalytic precursor for the 1-hexene hydroformylation reaction, in biphasic toluene/water medium (T = 100°C, syngas total pressure = 600 psi, pH₂/pCO = 1). Complex (1) showed good activity favoring the linear aldehyde. Likewise as other organic olefin substrates and with synthetic and real naphtha, good conversions to oxygenated products were obtained.     

Solvent and thiourea adsorption/intercalation effects on the solid-state electrochemistry of α-phase nickel hydroxide nanoparticles

Nanoparticles of α-phase nickel hydroxide were synthesized by a single-step hydrothermal method using urea as the hydrolytic agent. Precipitated powders were of pure turbostratic α-phase as confirmed by x-ray diffraction profile. The ageing of α-Ni(OH)₂ in 1.0 M alkali solutions is investigated for pure non-intercalated α-Ni(OH)₂ and thiourea intercalated/absorbed α-phase nanomaterials. The α-Ni(OH)₂ powder immobilized on the surface of graphite electrodes shows a gradual α→β phase transformation with continuous voltammetric cycling, and the concentration gradient of water that exists in the layered-double-hydroxide-like interlayers of α-phase and the solution was shown to play a crucial role on the high electrochemical activity of this phase nickel hydroxide. To understand the role of water in the ageing process, concomitant entries of non-aqueous solvents like ethanol and acetonitrile along with thiourea were effected. Cyclic voltammetric measurements of thiourea-treated α-Ni(OH)₂ samples revealed that hydroxyl ion influx during the anodic oxidation depends on the counter flux of solvent molecules, and if the intercalated the solvent is acetonitrile, then the electrochemical activity of α-Ni(OH)₂ reduced drastically; Q _a/Q _c>1 for water as solvent in the interlayers α-Ni(OH)₂ and Q _a/Q _c<1 for ethanol and acetonitrile as solvents. The α-phase gets stabilized in the presence of thiourea with water and ethanol as co-intercalates. Transmission electron microscope images of α-Ni(OH)₂ and thiourea-treated samples show a change in particle size and morphology. Elemental CHNS analysis confirms the presence of sulphur in the thiourea intercalated samples.     

Energy characteristics of adsorbed water in active carbons according to the NMR relaxation data

Nuclear magnetic relaxation measurements were used to determine activation energy E _act of the motion of water molecules adsorbed in active carbons. The E _act value was found to depend on the filling of active carbon pores due to changes in the state of water molecules under adsorption. It was established that the E _act = f(p/p _s) plots, where p/p _s is the relative pressure of water vapor observed for microporous active carbons (FAS-1, 2, N-15, SKT-6A), are similar in form to the corresponding plots of changes in water adsorption heats. In particular, we concluded that the plateau in the E _act = f(p/p _s) dependences, as in the case of adsorption heats, reflects the volumetric filling of active carbon micropores with water. We show that a linear function describes the increase in E _act values for water upon the complete filling of micropores with an increase in the volume of adsorbed water clusters per one primary adsorption center (W ₀/a _m ). We establish that, for water in the FAS-3 sample, the deviation of E _act values from this linear function was due to the contribution from the vapor phase in the mesopores (x ₀ = 0.7−1.2 nm) that make up a considerable part of the active carbon’s porous system.     

Coordination characteristics of trivalent lanthanides and actinides in molten hydrate salts of Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> and CaCl<Subscript>2</Subscript>

Distribution behavior of Ce(III), Am(III), and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO₃)₂·RH₂O or molten calcium chloride hydrate CaCl₂·RH₂O was studied radiochemically. In Ca(NO₃)₂·RH₂O systems, maximum separation factors of Ce and Cm to Am were observed to be 12 (Ce/Am) and 1.7 (Cm/Am). The distribution ratios of these elements increased with the decrease of water activity in the hydrates, and the extractabilities at the water deficient region was less sensitive compared to those at the water abundant region. This trend was similar to the coordination circumstance change observed in electronic absorption spectra of Nd(III) in the hydrates.     

Kinetics and mechanism of oxygen electroreduction on PtCoCr/C catalyst containing 20–40 wt % platinum

It is shown that the mechanism of oxygen electroreduction on the PtCoCr/C systems in 0.5 M H₂SO₄ is similar to that proposed for the Pt/C catalyst. The activity of ternary catalysts is by two and more times higher than that of monoplatinum catalyst. The constant k ₁ is much larger than k ₂ (k ₁ and k ₂ are the rate constants of O₂ reduction to water and H₂O₂, respectively) for all catalysts studied. This indicates that the catalytic systems are selective with respect to O₂ reduction immediately to water in the practically important potential range from 1.0 to 0.6 V. The yield of H₂O₂ increases with a shift of potential in the cathodic direction (<0.7 V) and does not exceed 1%. The sum of rate constants of further conversion of hydrogen peroxide also increases with a shift of potential in the cathodic direction. After a corrosion attack (a treatment in the acid for 24 h), a ratio between the rate constants (k ₁/k ₂) for the PtCoCr/C catalysts increases. This is caused by a considerable increase in k ₁, which is 2.84 × 10⁻² cm/s for the catalyst containing 34 wt % Pt (against 1.5 × 10⁻² cm/s for the untreated catalyst). This can be explained by the reaction proceeding on the particle surface, which was enriched in platinum in the course of corrosion treatment. The properties of platinum clusters on the alloy surface differ from those of monoplatinum as a result of the ligand effect. The amount of oxygen chemisorbed from water on this surface is lower than on Pt/C catalyst. This is the main factor determining an increase in the activity and stability of ternary catalysts.     

An Efficient,Visible‐Light‐Driven,Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/Zn_xCd_1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn_0.5Cd_0.5S exhibits an optimal HER rate of 16.78 mmol g⁻¹ h⁻¹ and high stability and recyclability under visible‐light irradiation (λ>420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.     

Comparative study of Cu(II) catalytic sites immobilized onto different polymeric supports

The catalysts with copper(II) ions stabilized onto different polymeric matrixes are prepared on either bulk (Cu/chitosan, Cu/polyethyleneimine-polyacrylic acid (PPA), and Cu-diiminate-impregnated polystyrene, polyarylate, or polymethylmethacrylate) or composite supports (egg-shell type Cu/chitosan/SiO₂ and Cu/PPA/SiO₂). The morphology of the samples and peculiarities of Cu(II) cationic sites are studied by SEM and ESR methods, and the catalyst activities are compared in oxidation of o- and p-dihydroxybenzenes by air in water. The catalytic activity of Cu(II) centers is governed by the coordination of isolated copper ions: for the most active catalysts, i.e., Cu/chitosan and Cu/PPA, the symmetry of isolated Cu²⁺-sites approximates a coordinatively unsaturated square-planar structure. At the same time, accessibility of active sites to water differs for different polymers, so the contribution of hydrophilicity to the reaction pattern cannot be excluded. Redox transformations of the active sites in the course of catalytic tests do not cause copper leaching from the polymer matrix. The binary composite systems with a film of low-loaded hydrofilic Cu-polymer supported on macroporous SiO₂ demonstrate substantially higher activity in oxidation of hydroquinone and 3,4-dihydroxyphenylalanine, as compared with the bulk Cu/polymer samples. In turn, the specific activity of Cu/chitosan/SiO₂ exceeds significantly that of Cu/PPA/SiO₂ due to stabilization of a thinner and more uniform film of chitosan at the surface of silica.     

Laccase behavior in the microenvironment of water core within a biosurfactant‐based reversed micelles system rhamnolipid/n‐hexanol/isooctane/water

Compared with synthetic surfactants (cetyltrimethyl ammonium bromide, sodium bis(2‐ethylhexyl) sulfosuccinate and Tween‐80), the properties of the aqueous core as well as the microenvironment behavior were investigated in water‐in‐oil microemulsions, which are formed by water and biosurfactant rhamnolipid (RL) in the solvent of isooctane/n‐hexanol (1:1, v/v). Besides, as a typical substrate of lignocellulose, guaiacol was used to detect the laccase activity in reversed micelles (RMs). The results were eventually confirmed that RL‐based RM system has higher solubilization ability, more friendly environmental compatibility and milder reaction microenvironment than the others. In this study, triangle phase diagram of surfactant/n‐hexanol/isooctane/water was constructed to analyze the variation of phase behavior between each RM system. For the RL‐based RM system, the effect of the molar ratio of water to surfactant (ω₀) on enzyme hydrolytic activity was also determined to be shown as a bell‐shaped curve and presented a maximum at ω₀ = 19; the O―H stretching vibrations of water in aqueous core was also studied by analyzing the IR spectrum over the region of 3050–3750 cm ^{? 1}. Moreover, kinetic studies showed that the catalytic efficiency of the laccase in RL‐based RM system was lower than in aqueous solution. Nevertheless, the RM system obtained the highest hydrolysis rate at RL concentration of 1.0CMC, which is 0.055 mM. Copyright © 2015 John Wiley & Sons, Ltd.