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Here we describe the apparatus developed in our laboratory for carbon monoxide (CO) oxidation studies dedicated to test thin film catalysts deposited on flat substrates. Our apparatus is original for its unique technical solutions, especially in continuous gas flow mode, and specifically as: (i) the sample holder is designed such that it can allow the gas flow to interact with the entire surface of the catalyst film to be utilized for the CO oxidation reaction, (ii) three different mass flow controllers permit a gas mixture of any composition during the measurement, (iii) CO to CO2 conversion is continuously monitored for long periods of time and can be tested in a wide range of temperatures (30–500 °C) with high accuracy on-line gas chromatography, and (iv) several security measures are guaranteed during the handling of CO gas. To test the efficiency of the apparatus, an experiment for CO oxidation was carried out at various temperatures using cobalt oxide cluster-assembled thin films synthesized by pulsed laser deposition over a glass substrate. [ABSTRACT FROM AUTHOR]

Abstract: Co3O4 nanoparticles assembled coatings have been synthesized by physical (pulsed laser deposition (PLD) and electron beam deposition) and chemical (sol–gel and electroless) techniques. The morphological, structural, and optical properties of all the coatings were analyzed by SEM, XRD, Raman spectroscopy, XPS, and UV–vis spectroscopy. The catalytic activities of the several Co3O4 heterogeneous catalyst coatings have been compared by looking at their efficiency on degradation of methylene blue dye that occurs via photo Fenton reaction in presence of H2O2 or oxone oxidants. The coating synthesized by PLD exhibits the best photo-degradation rate of dye in presence of H2O2 (4h) or oxone (8min). The NPs produced by PLD process exhibit smaller average size (18nm), narrow size distribution (σ =3nm), perfect spherical shape, low degree of agglomeration, and mixed amorphous-nanocrystalline phase. These special features of NPs, along with better visible light absorption, are the main factors responsible for the enhanced photocatalytic activity of the PLD Co3O4 NPs assembled coating. It is also observed that although the concentration of oxone (0.5mM) was very small as compared to H2O2 (100mM) the photo-degradation of MB dye solution is much faster for oxone. [Copyright &y& Elsevier]

Abstract: Cobalt oxide (Co3O4) nanoparticles (NPs) assembled coating have been prepared by reactive pulsed laser deposition of Co, in O2 atmosphere, on Si or glass substrate ranging from room temperature to 250°C. The NPs, having narrow size distribution with average values of around 25–50nm, were characterized by Raman, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The Co3O4 NPs synthesized at 150°C comprise a mixed amorphous–nanocrystalline phase (that is unique property for catalysis) while complete crystallization of Co3O4 occurs at 250°C with formation of spinel structure. Photocatalytic properties of Co3O4 NPs assembled coating for degradation of methylene blue solution under visible light irradiation are reported. The effect of H2O2 concentration and effect of pH variation on dye degradation rate has been reported. The reusability of the Co3O4 NPs assembled thin coating catalyst was further evaluated in several recycling runs. The activity of heterogeneous Co3O4 NPs assembled thin coating catalyst was compared with homogenous catalyst producing Co+2 ions in methylene blue solution. [Copyright &y& Elsevier]

Highlights: [•] V–N-codoped TiO2 thin films have been prepared using RF-magnetron sputtering. [•] The band gap was narrowed up to 2.5eV when V and N were codoped in TiO2. [•] V–N-codoped TiO2 thin film was able to degrade organic water pollutants much faster than mono-doped and undoped TiO2. [•] Increased visible light absorption and charge separation are mainly responsible for enhanced photocatalytic activity for codoped-TiO2. [ABSTRACT FROM AUTHOR]