Limiting resources of fossil fuels and environmental issues inevitably require more efficient utilization of solar energy. Photocatalytic production of hydrogen is identified as one of the most promising routes for developing clean and sustainable energy. However, engineering of low-cost materials exhibiting high catalytic activity in the entire range of solar spectrum is still a challenge. Here we report, for the first time, simple, easily scalable and environmentally friendly synthesis of stable Ti@TiO 2 core-shell nanoparticles exhibiting photocatalytic activity in hydrogen production under Vis/NIR light irradiation without any noble metals. Stable to oxidation core-shell Ti@TiO 2 nanoparticles have been obtained by the simultaneous actions of ultrasound and hydrothermal treatment on air-passivated titanium metal nanoparticles in pure water. The obtained material is composed of quasi-spherical Ti particles (20-80 nm) coated by 5-15 nm crystals of defect-free anatase with small amounts of rutile. In contrast to pristine TiO 2 , the Ti@TiO 2 nanoparticles extend the photo response from UV to NIR light region due to the light absorption by nonplasmonic Ti core. In MeOH-H 2 O solutions, the Ti@TiO 2 nanoparticles exhibit the strongest catalytic activity in H 2 formation under joint effect of Vis/NIR light and heat. Isotopic study using MeOH-D 2 O solutions suggested the reaction mechanism involving electron holes accumulation in semiconducting TiO 2 shell via charge separation and multiple charge-transfer steps that follow Ti interband transition. The electron transport from Ti core presumably occurs through the junctions between TiO 2 crystals at the surface of core-shell nanoparticles.

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The present work analyses the mechanism of W(2)C/C nanocomposite formation during sonolysis of W(CO)(6) in diphenylmethane (DPhM) solutions. Carbon supported WC(x) nanoparticles attract much interest as an alternative fuel cell electrocatalysts. Sonolysis of neat DPhM under the effect of 20 kHz power ultrasound in argon at 80 °C yields a sonopolymer as a solid product and acetylene, hydrogen, methane, diacetylene and benzene as gaseous products. Diacetylene is formed due to the secondary sonochemical dimerisation of acetylene obtained at the primary stage of DPhM sonolysis. FTIR and μ-Raman studies show that the sonopolymer consists of a mixture of some polymeric partially oxidized aromatic species, and disordered carbon. Sonolysis of W(CO)(6) in diphenylmethane solutions follows the first order kinetics. This process yields monodispersed 2-3 nm X-ray amorphous WC(x) nanoparticles embedded in amorphous sonopolymer. The annealing of air sensitive as-prepared solids in an inert atmosphere at 600 °C causes formation of stable W(2)C/C nanocomposite with W(2)C average particle size in the range of 4-7 nm and hexagonal carbon fine particles with the average size of 30-40 nm. Kinetic study revealed that tungsten carbide is formed inside the cavitation bubble due to the reaction of tungsten nanoparticles originated from primary sonolysis of W(CO)(6) with acetylene produced as a result of diphenylmethane sonochemical degradation.

Porous (Ce0.5Zr0.5)O2 solid solutions were prepared by thermolysis (T=285 °C) or sonolysis (20 kHz, I=32 W cm(-2), Pac=0.46 W mL(-1), T=200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4-6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce0.5Zr0.5)O2 solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m(2) g(-1) depending on synthesis conditions. The use of Barrett-Joyner-Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce0.5Zr0.5)O2 mixed oxides loaded with 1.5%wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.