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In this paper, the interaction between cobalt oxides (Co3O4 and CoO) and methanol is studied. CoO was obtained by heating under high-vacuum (HV) conditions and characterized by X-ray photoelectron spectroscopy (XPS). The Co3O4 powder sample was characterized by means of XPS, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), and thermal analysis. The interaction between Co3O4 and methanol was studied both at atmospheric pressure (by means of DRIFT spectroscopy) and under HV conditions (by means of XPS and quadrupolar mass spectroscopy, QMS), whereas the chemisorption of methanol on the CoO surface was studied only under HV conditions. Methanol chemisorbs mainly molecularly on the cobalt oxide surfaces, the alcohol dissociation being more evident at higher temperatures. In the case of Co3O4, the formation of formate and polymers of formaldehyde is evident around 473−523 K, whereas under HV conditions, formaldehyde and several decomposition and fragmentation products were observed as well as carbon oxides. Similar results were obtained in the case of CoO.

N-type metal oxide solar cells sensitized by infrared absorbing PbS quantum dots (QDs) represent a promising alternative to traditional photovoltaic devices. However, colloidal PbS QDs capped with pure organic ligand shells suffer from surface oxidation that affects the long term stability of the cells.Application of a passivating CdS shell guarantees the increased long term stability of PbS QDs, but can negatively affect photoinduced charge transfer from the QD to the oxide and the resulting photoconversion efficiency (PCE). For this reason, the characterization of electron injection rates in these systems is very important, yet has never been reported. Here we investigate the photoelectron transfer rate from PbS@CdS core@shell QDs to wide bandgap semiconducting mesoporous films using photoluminescence (PL) lifetime spectroscopy. The different electron affinity of the oxides (SiO 2 , TiO 2 and SnO 2 ), the core size and the shell thickness allow us to fine tune the electron injection rate by determining the width and height of the energy barrier for tunneling from the core to the oxide.

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La0.6Sr0.4Co1−y FeyO3−δ (y = 0.2, 0.5, 0.8) perovskite-type oxide powders were prepared by the citrate gel method with the aim of investigating the influence of cobalt/iron atomic ratio on the chemical and structural properties as well as on the catalytic activity. The samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal analysis, Kr physisorption surface area, scanning electron microscopy (SEM), and temperature programmed reduction (TPR). XRD outcomes reveal the formation of perovskite phase after calcination at 873 K. Depending on the Co/Fe atomic ratio, the perovskite exhibits two different structure: rhombohedral for y < 0.5, orthorhombic for y ≥ 0.5. However, other phases are also observed. The crystallite size increases with the calcination temperature, while decreases with the iron content. The specific surface area of the La0.6Sr0.4Co1−y FeyO3-δ perovskites (calcined at 1073 K) is low, but increases with the iron amount: it varies between 4.1 and 6.6 m2 g−1 moving from y = 0.2 to y = 0.8. XPS results reveal the presence of traces of Co(II) in the sample with lower cobalt amount. The scanning electron micrographs reveal nanoscaled near spherical particles which are clustered together, forming a highly porous microstructure. However, the samples with higher iron content show a more compact morphology due to the enhanced agglomeration. The perovskite phase is rather stable even after aggressive treatment as high temperature reduction. The influence of cobalt/iron atomic ratio on the catalytic activity toward alcohol steam reforming was investigated. All the samples present good alcohol dehydrogenation activity, as resulting from the methanol steam reforming experiments. In the steam reforming of ethanol, the La0.6Sr0.4Co0.5Fe0.5O3-δ presents the better performance (especially after reduction at 873 K) with the complete conversion of ethanol into syngas above 850 K and the almost complete suppression of the ethylene formation at lower temperature. The differences of the activity toward ethanol steam reforming are attributable to a different stabilization of Co(0) nanoparticles produced during the reduction at 873 K.

Three nanostructured cerium(IV) oxide powders were synthesized by two different synthetic routes: two samples were obtained by precipitation from a basic solution of cerium nitrate and treated at 523 and 923 K, respectively, and the third one was prepared by a microwave-assisted heating hydrolysis method and treated at 523 K. The obtained samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron (XPS), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic techniques, thermal analysis, and Brunauer-Emmett-Teller (BET) surface area. A broad particle size distribution is observed for CeO 2 obtained by precipitation (8.0-15.0 nm). Smaller particles (sizes around 3.3-4.0 nm) with a narrow particle size distribution characterize the ceria obtained by microwave irradiation. XPS and DRIFT outcomes show that (i) the CeO 2 prepared by microwave-assisted heating hydrolysis method is more reduced than that obtained by precipitation and treated at the same temperature; (ii) the CeO 2 obtained by precipitation and treated at 923 K is more reduced than that prepared by microwave irradiation. A higher amount of basic and acidic sites were noticed on the CeO 2 obtained by microwave irradiation. Methanol interacts mainly dissociatively with the CeO 2 surface regardless of the preparation procedure and reduction degree of surface; however, on the CeO 2 prepared by microwave irradiation the interaction is quantitative: all the methanol introduced in the reaction chamber reacts with the surface. The CeO 2 obtained by precipitation and treated at 523 K does not oxidize methanol, even at higher temperature, while traces of oxidation products are noted on the sample treated at 923 K. Methanol oxidation is favored on the CeO 2 prepared by microwave irradiation: the main oxidation products are formate species and inorganic carboxylate. Moreover, the oxidation capability increases with increasing temperature.

The interaction between methanol and a NiO powder sample was studied. The obtained NiO was characterized by means of X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), and thermal analysis. Chemisorption experiments at atmospheric pressure were studied by means of diffuse reflectance infrared spectroscopy, whereas those carried out under high vacuum (HV) conditions were followed by means of XPS and quadrupolar mass spectrometry (QMS). Methanol interacts mainly molecularly with the NiO powder surface whereas dissociative chemisorption is more evident at higher temperatures. The formation of CO2 and of formate species is evident at T ≥ 323 and 423 K, respectively. Under HV conditions formaldehyde forms at higher temperatures.