Abstract

Nanocrystalline Bi₂MoO₆ photocatalysts were successfully synthesized by conventional solvothermal and microwave–solvothermal routes, respectively. The prepared samples were characterized by X-ray diffraction, BET surface area analysis, UV–vis diffuse reflectance spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The samples have high surface areas in the range of 10–32 m² g⁻¹. Their average crystallite sizes are in the range of 16–35 nm. The absorption edge of the samples is at ∼491 nm, corresponding to a band gap energy of about 2.53 eV. Different morphologies with nanosheets and nanorods were also observed. The photocatalytic activities of Bi₂MoO₆ photocatalysts were evaluated by the decomposition of Rhodamine B under visible-light irradiation (λ > 420 nm). Nanocrystalline Bi₂MoO₆ samples obtained via different conditions exhibited different photocatalytic performances. The effects of the crystallinity, specific surface area and morphology of the samples on the photocatalytic activities are also discussed.

The reaction of ferrocene with the acidic hydroxy groups in the supercages of zeolite HY dehydrated at 673 K and the reactivity of the resultant surface species towards CO and O₂ were investigated by temperature-programmed decomposition (TPD) and reduction (TPR) and IR, X-ray absorption fine structure analysis (XAFS), and X-ray photoelectron (XP) spectroscopy. In situ FTIR, TPD, TPR, and chemical analysis reveal that the Cp₂Fe molecule adsorbed on the zeolite surface loses one cyclopentadienyl group under vacuum at 423 K, which leads to the formation of a well-defined mononuclear surface Fe-C₅H₆ complex grafted to two acidic sites and one (Si-O-Si) unit, as confirmed by the lack of Fe–Fe contributions in the EXAFS spectra. Each iron atom is coordinated, on average, to three oxygen atoms of the zeolite surface with a FeO distance of 2.00 Å and to five carbon atoms with a FeC distance of 2.09 Å. IR spectra indicate that the cyclopentadiene–iron species grafted on the surface of the zeolite is quite stable in vacuo or under an inert or hydrogen atmosphere below 423 K, and is also relatively stable under oxygen at room temperature. However, the cyclopentadiene ligand readily reacts with CO to form a compound containing carbonyl at 323 K, and even at room temperature. The single carbonyl band in the IR spectra provides evidence for the nearly uniform formation of a cyclopentadiene–iron species on the surface of the zeolite.

Mesoporous solid superacid molecular sieve films have been prepared (see Figure) and used as photocatalysts. The new class of superacid possesses large surface area, uniform pore size, and accessible 3D mesoporous architecture. These are attractive properties for catalytic or photocatalytic applications.