S. Ardizzone
University of Milan
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Featured researches published by S. Ardizzone.
Electrochimica Acta | 1990
S. Ardizzone; G. Fregonara; S. Trasatti
Abstract The dependence of the voltammetric surface charge q* on solution pH and potential scan rate has been investigated using a set of RuO2 electrodes prepared by thermal decomposition of RuCl3 at temperatures in the range 300–500°C. The systematically higher charge in KOH than in HClO4 in the same potential range (vs rhe) is attributed to the stabilization of higher oxidation states of surface Ru atoms in the alkaline environment. The variation of q* with v, the potential scan rate, is shown to be linearizable as a function of v 1 2 . It is thus possible to extrapolate the values of q* to v=0 and v=∞, respectively. The extrapolation enables an “inner” surface to be discriminated from an “outer” surface. The former is pointed out to be composed by the regions of difficult accessibility for the proton-donating species assisting the surface redox reactions. Reasons why the “screened” surface appears to be higher in alkaline than in acid solutions, are discussed. It is stressed that only working with a set of RuO2 electrodes prepared at different temperatures it is possible to discover meaningful correlations.
Applied Surface Science | 1997
S. Ardizzone; Claudia L. Bianchi; M. Fadoni; B. Vercelli
Abstract XPS measurements have been performed on a series of Mg II salts (NO 3 − , CO 3 2− , SO 4 2− , Cl − , CH 3 COO − ), hydroxides and oxides, these latter compounds are both commercial and prepared in laboratory. The binding energy (BE) of the anionic partner in Mg II salts compares well in any case with literature data for the same anions in other alkaline and alkaline earth compounds. The BE of Mg II appears to be affected by the electroattractive nature of the parent anion. The Mg II spectra, in the case of MgO samples, are not influenced either by the nature of the oxide precursor salt or by the temperature of the oxide preparation (873 K, 1073 K, 1253 K). The BE of Mg 2p ranges between 49.9 eV and 50.2 eV. Oxygen spectra are regular and show the presence of the surface chemisorbed -OH component even at heating temperatures of 1473 K. The choice, as internal reference, of the hydrocarbon contaminant carbon peak is discussed, specifically, in the case of MgO samples with reference to specific lattice and surface properties of the oxide itself.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | 1998
S. Ardizzone; Claudia L. Bianchi; D. Tirelli
Abstract The paper reports data relative to the preparation of Mn 3 O 4 and γ-MnOOH powders by following hydrothermal procedures. The mixed valence spinel was prepared starting either from manganous sulphate or chloride and oxidising in suspension (by either air or oxygen) the alkaline precipitate. Manganite was obtained by oxidising manganous sulphate solutions with H 2 O 2 , subsequent alkalisation and refluxing. The samples were characterised for phase composition by X-ray diffraction. Pure phase oxides were obtained in the case of both Mn 3 O 4 and γ-MnOOH when Mn(II) sulphate was used as the precursor. The pure phase samples were submitted to X-ray photoelectron spectroscopy (XPS) investigation, in the case of manganese, for both 2p and 3s spectral regions. The binding energies of the un-fitted experimental Mn peaks compare well with the relative values reported in the literature for the compounds. With the aim of assessing the actual Mn speciation, in the external layers, the fitting procedure of the experimental XPS peaks has been performed by modulating the relative intensities of the spectral components on the grounds of distinct hypotheses consistent with the oxide formulas. The possibility of extending the outcome of this elaboration to the bulk composition of the samples is also discussed.
Journal of Electroanalytical Chemistry | 1997
G. Spinolo; S. Ardizzone; S. Trasatti
Abstract Co3O4 layers on an Ni support were prepared by the sol-gel method. Their properties were characterized by TGA, XRD and SEM. For comparison, Co3O4 was also prepared by thermal decomposition of Co nitrate. The surface electrochemical response was studied in alkaline solution by cyclic voltammetry at several potential scan rates. The electrochemical analysis included the open circuit potential, the voltammetric peak potentials, and the voltammetric charge. Extrapolation of the charge to scan rates ν = 0 and ν = ∞ allowed the ‘electrochemical porosity’ to be estimated. The results suggest that Co3O4 from the sol-gel method is less crystalline and more porous, although the highest difference in terms of surface charge with respect to the oxide from the nitrate is only a factor of 2.
Cellulose | 1999
S. Ardizzone; F. S. Dioguardi; Torquato Mussini; Patrizia R. Mussini; Sandra Rondinini; B. Vercelli; Alberto Vertova
Characterization of an Avicel PH 102 MCC powder through polymerization degree determination, X‐ray diffraction and N2 adsorptions at subcritical temperatures is described. Specific characterizations of MCC/H2O exchange in different environments were performed by means of thermogravimetric weight losses on time/temperature scale and analyses of water adsorption/absorption from saturated vapors at 310 K. The reversibility of MCC/H2O interactions and the influence of different ‘surface area probes’ on the specific surface area are discussed.
Nanoscale Research Letters | 2009
Giuseppe Cappelletti; S. Ardizzone; Claudia L. Bianchi; Stefano Gialanella; Alberto Naldoni; Carlo Pirola; V. Ragaini
Nanocrystalline TiO2samples were prepared by promoting the growth of a sol–gel precursor, in the presence of water, under continuous (CW), or pulsed (PW) ultrasound. All the samples turned out to be made of both anatase and brookite polymorphs. Pulsed US treatments determine an increase in the sample surface area and a decrease of the crystallite size, that is also accompanied by a more ordered crystalline structure and the samples appear to be more regular and can be considered to contain a relatively low concentration of lattice defects. These features result in a lower recombination rate between electrons and holes and, therefore, in a good photocatalytic performance toward the degradation of NOxin air. The continuous mode induces, instead, the formation of surface defects (two components are present in XPS Ti 2p3/2region) and consequently yields the best photocatalyst. The analysis of all the characterization data seems to suggest that the relevant parameter imposing the final features of the oxides is the ultrasound total energyper volume (Etot/V) and not the acoustic intensity or the pulsed/continuous mode.
Journal of The Electrochemical Society | 1989
S. Ardizzone; Marco Falciola; S. Trasatti
Ruthenium nitrosyl nitrate has been used as a precursor to prepare Cl-free RuO/sub chi/ with the scope of investigating the role of the residual chlorine present in RuO/sub chi/ obtained by thermal decomposition of RuCl/sub 3/. Ti-supported layers were prepared in the temperature range 270{sup 0}-500{sup 0}C. Surface and electrocatalytic properties have been investigated by means of voltammetric curves. Tafel plots, reaction order, and activation energy determinations. The results show that Cl-free RuO/sub chi/ does not behave differently from RuO/sub chi/ containing Cl, although both the range of temperature where the stable oxide is formed and the surface morphology depend on the nature of the precursor.
Surface and Interface Analysis | 2000
S. Ardizzone; Claudia L. Bianchi
Sulphated zirconia powders have been prepared by impregnation, with either sulphuric acid or ammonium sulphate, of hydrous precursors precipitated at room temperature. Iron-promoted samples were prepared by mixing the sulphated zirconium hydroxide with ferric nitrate solutions. Samples containing increasing amounts of iron, in the absence of sulphates, were also obtained. All the samples have been calcined at the same temperature (470°C) and for the same length of time (5 h), and have been characterized as to phase composition (using x-ray diffraction) and surface area (using BET). The acidity features of the powders were obtained by a revised Hammett-Bertolacini technique and the sulphur and iron contents were obtained by elemental analyses. X-ray photoelectron spectroscopy analyses of the samples have been obtained by elaboration of the S 2p and Zr 3d spectral regions. The outcome of the fitting procedures of the Zr 3d doublet of the different samples is presented and commented on in relation to the possible role played by sulphates and iron in the features of the oxide active surface sites.
Electrochimica Acta | 1995
S. Ardizzone; G. Spinolo; S. Trasatti
Abstract Co3O4 has been prepared by thermal decomposition of basic CoCO3 in the temperature range 200 to 800 °C. The pzc has been measured by potentiometric titration and has been found to coincide with the iep determined by microelectrophoresis. The pzc is constant at ca. 7.3 between 200 and 450 °C. The GCSG model of the electrical double layer has been applied to the experimental data to derive the real surface area of the oxide and the inner layer capacitance. The electrochemical surface area coincides with BET data. The results of this work have been compared with those obtained previously with Co3O4 prepared by thermal decomposition of the nitrate.
Journal of Electroanalytical Chemistry | 2003
Patrizia R. Mussini; S. Ardizzone; Giuseppe Cappelletti; Mariangela Longhi; Sandra Rondinini; L. M. Doubova
Abstract The silver surface screening effects by specifically adsorbed halide anions in the electrocatalytic reduction of a model organic bromide (acetobromoglucose) have been studied by cyclic voltammetry on controlled mono- and polycrystalline silver surfaces in acetonitrile+0.1 M tetraethylammonium perchlorate medium as a function of the concentration c X of added TEAX (X=Cl, Br, or I, TEA, tetraethylammonium). The reduction peak potentials, E p , are regularly shifted in the negative direction with increasing c X , typically tending to an asymptotic value for c X ≈0.1 M. Several literature models describing adsorption/desorption equilibria have been applied to justify the above experimental E p versus c X trends (being logarithmic in the iodide cases) for the three halides and the four silver surfaces tested.