Efficient catalytic decomposition of sulfuric acid with copper vanadates as an oxygen-generating reaction for solar thermochemical water splitting cycles.

Copper pyrovanadate (Cu(2)V(2)O(7)) was found for the first time to achieve the high catalytic activity for the decomposition of sulfuric acid to evolve O(2) at moderate temperatures around 650 °C, which is essential for the development of solar thermochemical water splitting cycles.

Hydrothermal synthesis of a doped Mn-Cd-S solid solution as a visible-light-driven photocatalyst for H2 evolution.

The effect of metal doping (i.e., with Cr, Fe, Ni, Cu, Zn, Ag and Sn) on the crystal structure of hydrothermally synthesized Mn(1-x)Cd(x) S (where x≈0.1) is studied with the aim of enhancing photocatalytic activity. In contrast to the low-crystalline, undoped solid solution Mn(1-x)Cd(x)S, Ni doping yields a well-crystallized wurtzite-type Mn-Cd-S solid solution, which precipitates as planar hexagonal facets of several hundred nanometers in size, together with much larger grains of α-MnS (>10 µm). By removing inactive α-MnS through sedimentation, a single phase with composition of Ni(0.01)Mn(0.56)Cd(0.43)S is obtained successfully. The Ni doping achieved a threefold higher photocatalytic activity for H(2) evolution from a 0.1 M Na(2)S/0.5 M Na(2)SO(3) solution under visible-light irradiation (λ≥420 nm). The apparent quantum yield of 1 wt % Pt-loaded Ni(0.01)Mn(0.56)Cd(0.43)S measured at λ=420 nm reached 25 %. The enhanced photocatalytic activity is most likely the result of a decreased concentration of defects, responsible for electron-hole recombination, in the active solid-solution phase and a slightly higher bandgap energy (2.4 eV).

Catalytic activity and regeneration property of a Pd nanoparticle encapsulated in a hollow porous carbon sphere for aerobic alcohol oxidation.

A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N(2) adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.8 nm in diameter) systems. When compared to some Pd-supported carbons, Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O(2) as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles, leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.

Drastic changes in photoluminescence properties of multilayer films composed of europium hydroxide and titanium oxide nanosheets.

Multilayer films consisting of Eu(OH)(3-x) and titanium oxide nanosheets showed strong Eu(3+) emission under UV-light irradiation, in which the titanium oxide nanosheet works as an antenna collecting UV-light, and then the Eu(OH)(3-x) nanosheet acts as an emitting layer receiving the absorbed energy.

An exploration of nitrate concentrations in groundwater aquifers of central-west region of Bangladesh.

Groundwater and river water samples were collected from the study area to investigate the spatial distribution of nitrate (NO(3)(-)) in the central-west region of Bangladesh. The shallow and deep groundwater nitrate concentrations ranged from <0.10 to 75.12 and <0.10 to 40.78 mg/L, respectively. Major river water NO(3)(-) concentrations were ranged from 0.98 to 2.32 mg/L with an average of 1.8 mg/L. The average Cl(-)/NO(3)(-) ratio (4.9) of major river water has been considered as reference point to delineate denitrification processes. The alluvial fan, alluvial, deltaic and coastal deposits shallow groundwater having C1(-)/NO(3)(-) values less than that of the average river water value (4.9), suggested denitrification processes within the aquifers. On the other hand, denitrification processes are insignificant in the Pleistocene terraces area aquifers related to relatively higher concentrations of nitrate. Iron pyrite has been found as insignificant effect on denitrification.

Electrocatalytic nitrate hydrogenation over an H+ -conducting solid polymer electrolyte membrane-modified cathode assembly.

Selective electrocatalytic hydrogenation of NO3- to N2 in water has successfully been achieved at room temperature using a membrane-electrode assembly (MEA) consisting of an H+ -conducting solid polymer electrolyte (Nafion-117) and a surface-modified Pt cathode.

Asymmetrically modified silica particles: a simple particulate surfactant for stabilization of oil droplets in water.

Spherical silica particles that are able to assemble at a phase boundary of a dual-phase mixture of water and an immiscible organic solvent were prepared by a partial modification of their surface hydroxyl groups with an alkylsilylation agent. Scanning electron microscopic observation of these particles in which their remaining surface hydroxyl groups had been selectively modified with colloidal gold particles revealed that each particle has an asymmetric surface structure: one side of the surface is hydrophilic and the other is hydrophobic. We found that these particles could form a micellar structure in water in the presence of an organic solution of a toluene/polystyrene mixture. The micellar structure was evidenced by formation of golf-ball-like polystyrene particles with dimples imprinting morphologies of the hydrophobic part of modified silica particles.

Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta3O10 (M = Cs, Na, H, and C6H13NH3).

The Dion-Jacobson series of triple-layered perovskite tantalates (MCa2Ta3O10, M = Cs, Na, H, and C6H13NH3) were synthesized to evaluate their photocatalytic activity for overall water splitting to evolve H2/O2 under UV irradiation. The photocatalytic activity was susceptible to the hydration of interlayer space. The hydrous Na phase exhibited much higher activity (H2: 308 micromol.h(-1)) compared to the anhydrous Cs phase (24 micromol.h(-1)) and the hydrous H phase (22 micromol.h(-1)) in the presence of 0.5 wt % Ni impregnated. H2O/D2O isotopic experiment suggested that the hydrated interlayer plays as an active site for water splitting, where the high mobility of water molecule in the interlayer should correlate with the total photocatalytic activity. The FLAPW electronic structure calculation demonstrated that the terminating oxygen site, O4, which faces to the interlayer space, contributes largely to the top of the valence band. Judging from comparison with the double-layered tantalates, MLaTa2O7, in our previous study, the contribution of terminating oxygen site to the band structure is supposed to depend on the number of perovskite layers.