In this study, relationships between preparation conditions, structure, and activity of Pt-containing TiO2 photocatalysts in photoinduced reforming of glycerol for H2 production were explored. Commercial Aerolyst® TiO2 (P25) and homemade TiO2 prepared by precipitation-aging method were used as semiconductors. Pt co-catalysts were prepared by incipient wetness impregnation from aqueous solution of Pt(NH3)4(NO3)2 and activated by calcination, high temperature hydrogen, or nitrogen treatments. The chemico-physical and structural properties were evaluated by XRD, 1H MAS NMR, ESR, XPS, TG-MS and TEM. The highest H2 evolution rate was observed over P25 based samples and the H2 treatment resulted in more active samples than the other co-catalyst formation methods. In all calcined samples, reduction of Pt occurred during the photocatalytic reaction. Platinum was more easily reducible in all of the P25 supported samples compared to those obtained from the more water-retentive homemade TiO2. This result was related to the negative effect of the adsorbed water content of the homemade TiO2 on Pt reduction and on particle growth during co-catalyst formation.
An ecofriendly, microwave (MW) promoted and solventless method is described for the alkylation of diethyl malonate, ethyl acetoacetate and ethyl cyanoacetate by a variety of alkyl halides in the presence of K 2 CO 3 . In the solidliquid phase alkylation of active methylene containing substrates, it seems to be of general value that the phase-transfer catalyst, that is an onium salt in the present case, can be omitted and substituted by MW irradiation promoting the formation of the potassium salt of the substrate and its transfer to the organic phase. In certain cases, the use of triethylbenzylammonium chloride led to the formation of by-products under the conditions (~160 °C/~12 bar) applied.
Employing an optimized Pd-catalyzed cross-coupling reaction promoted by CuI, novel Nferrocenylpyridazinones along with N-phenyl-and N-(2-pyridyl) analogues were synthetized from readily available heterocyclic precursors, iodoferrocene, iodobenzene and 2bromopyridine. Except for the ferrocenylation of 6-ferrocenylpyridazin-3(2H)-one yielding both N-and O-substituted products, the studied reactions exclusively afforded N-aryl lactams. The novel compounds exhibited cytotoxicity on HEPG2 and HT-29 human malignant cells under in vitro conditions. The measured IC50 values supplemented with the results of cyclic voltammetry and DFT calculations suggest that the cytotoxic activity of the N-and O-ferrocenyl-substituted derivatives and the decreased effect of the N-phenyl analogues seem to be at least partly associated with the potential to generate reactive oxygen species (ROS). This interpretation, allowing to predict characteristic substituent-dependent SAR, was supported by the results of related studies on the practically inactive N-(2-pyridyl)pyridazinones assumed to be present in protonated chelate forms with highly decreased propensity to undergo ionization.
Graphite-oxide/TiO 2 (GO/TiO 2 ) composite materials were prepared by heterocoagulation method from Brodie's graphiteoxide (GO) in order to test them as catalysts in the methanol photocatalytic reforming reaction in liquid phase. The preparation of the composite itself resulted in only little changes in the structure of GO as it was indicated by attenuated total reflection infrared (ATR-IR) and 13 C magic-angle spinning nuclear magnetic resonance ( 13 C MAS NMR) spectroscopic measurements. However, during the photocatalytic reaction, all of the GO/TiO 2 samples darkened strongly indicating structural changes of GO. X-ray photoelectron spectroscopy along with NMR confirmed the loss of oxygen functionalities and emergence of graphitic species in the samples recovered from the photocatalytic reaction. Model experiments were designed to identify the key factors determining the activity of the GO/TiO 2 derived photocatalysts. It was found that the emergence of a pronounced coupling between TiO 2 and the graphite-like carbonaceous material is the most important contribution to get active and stable photocatalysts.
The influence of the semiconductor microstructure on the photocatalytic behavior of Pt-PtOx/TiO2 catalysts was studied by comparing the methanol-reforming performance of systems based on commercial P25 or TiO2 from sol–gel synthesis calcined at different temperatures. The Pt co-catalyst was deposited by incipient wetness and formed either by calcination or high-temperature H2 treatment. Structural features of the photocatalysts were established by X-ray powder diffraction (XRD), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS), optical absorption, Raman spectroscopy and TEM measurements. In situ reduction of Pt during the photocatalytic reaction was generally observed. The P25-based samples showed the best H2 production, while the activity of all sol–gel-based samples was similar in spite of the varying microstructures resulting from the different preparation conditions. Accordingly, the sol–gel-based TiO2 has a fundamental structural feature interfering with its photocatalytic performance, which could not be improved by annealing in the 400–500 °C range even by scarifying specific surface area at higher temperatures.
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