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In order to deepen the understanding of the role of transition metal oxides in electron transfer at the electrochemical interface, the performance of ZnxNi1−xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanomaterials in electrochemical sensing is studied. Nanomaterials are synthesized by simple autocombustion synthesis procedure. Field‐emission scanning electron microscopy characterization shows that the particles have a size between 30 and 70 nm with an average crystallite size between 24 and 35 nm. The bandgap energies of the nanomaterials, as estimated by UV–vis experiments, are in the 2.32–2.56 eV range. The valence band maximum is evaluated using X‐ray photoelectron spectroscopy and the position of the conduction band minimum is estimated. The ZnFe2O4 sensor has the best performances: highest rate constant (13.1 ± 2.8 ms−1), lowest peak‐to‐peak separation (386 ± 2 mV), and highest sensitivity (37.75 ± 0.17 μA mM−1). Its limit of detection (7.94 ± 0.04 μM) is second best, and its sensitivity is more than twice the sensitivity of the bare sensor (16.7 ± 0.9 μA mM−1). Nanomaterials energy bands mapping with the experimental redox potentials is performed to predict the electron transfer at the electrochemical interface, and the importance of surface states/defects is highlighted in the electron transfer mechanism. [ABSTRACT FROM AUTHOR]

Different sol‐gel synthesis methods were used to obtain four nanostructured mesoporous TiO2 samples for an efficient photocatalytic degradation of the emerging contaminant N‐phenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO2 samples were obtained by means of as many template‐assisted syntheses, whereas other two TiO2 samples were obtained by a greener template‐free procedure, implying acidic conditions and, then, calcination at either 200 °C or 600 °C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO2 samples were characterized by X‐ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N2 adsorption/desorption at −196 °C; Diffuse Reflectance UV/Vis spectroscopy and ζ‐potential measurements. A commercial TiO2 powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pHIEP (pH at isoelectric point), whereas the samples band‐gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N‐phenylurea degradation, which are ascribed to their different physico‐chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions. [ABSTRACT FROM AUTHOR]

Detailed analysis of recently reported variable‐temperature IR (VTIR) spectra of carbon monoxide adsorbed in alkaline zeolites shows how, not only the corresponding values of standard adsorption enthalpy (ΔH0) and entropy (ΔS0) can be obtained, but also the thermodynamic values of molar entropy and enthalpy which characterize the adsorbed gas phase. In addition, it is shown that the so obtained molar entropy data can lead to new insights into soft molecular modes, which would be hardly accessible by conventional IR spectroscopic techniques. [ABSTRACT FROM AUTHOR]

Copper doped‐TiO2 (P25) nanomaterials have been intensively studied as promising catalysts for H2 production by photo‐reforming of selected organic compounds. However, the role of copper oxidation states on the improvement of photocatalytic activity is still debated. In this work, CuOx‐impregnated P25‐TiO2 catalysts were used for photocatalytic production of hydrogen from methanol. Copper species/oxidation states both in the as‐prepared catalysts and after the photocatalytic process were investigated. To this purpose, H2 production rates were correlated to physico‐chemical properties of the samples, both before and after photocatalytic process, by means of Raman, X‐Ray Diffraction, Electron Paramagnetic Resonance spectroscopy, X‐Ray Photoelectron Spectroscopy, Temperature‐Programmed Reduction and High Resolution Transmission Electron Microscope techniques. Results revealed the presence of both Cu2O and CuO deposits on the samples surface after calcination. Notably, under near‐UV irradiation, the fraction of highly dispersed CuO particles undergo a partial dissolution process, followed by reduction to metallic copper Cu(s) by photogenerated electrons, boosting H2 production rate. Our findings indicate that both Cu2O and Cu(s) act as co‐catalysts for H2 generation, yet by different mechanisms. Overall this study, provides the basis to enhance catalytic performance of red‐ox active systems through UV‐irradiation approach. [ABSTRACT FROM AUTHOR]

A mixed-oxide nanomaterial with composition (RuO2)0.038(Nb2O5)0.024(SiO2)0.938 was prepared by a one-pot sol-gel route. The synthesis was entirely performed at room temperature, by using easy-to-handle precursors and avoiding the employment of any toxic and/or polluting reactant. One of the samples was synthesised in the presence of a non-ionic surfactant acting as both pore directing agent and metal complexing agent, obtaining a high-specific-surface-area material characterized by a very good dispersion of the metallic species. In both cases, nanomaterials characterized by a complete reducibility of Ru species were obtained. The reduced nanomaterials acted as effective bifunctional catalysts in the hydrogenation of levulinic acid (LA) to γ-valerolactone, performed under mild conditions in the aqueous phase. The catalyst prepared without surfactant showed good stability and no activity loss during all the performed cycles. By contrast, some deactivation phenomena took place with the surfactant-templated catalyst. These phenomena were ascribed to both the partial surface oxidation and the surface adsorption of LA molecules giving deactivation during the second run. [ABSTRACT FROM AUTHOR]