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Dive into the research topics where A. Di Paola is active.

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Featured researches published by A. Di Paola.


Catalysis Today | 2002

Photocatalytic degradation of organic compounds in aqueous systems by transition metal doped polycrystalline TiO2

A. Di Paola; E. García-López; Shigeru Ikeda; Giuseppe Marcı̀; Bunsho Ohtani; Leonardo Palmisano

Abstract Some probe catalytic photooxidation reactions with aliphatic and aromatic organic compounds having different acid strengths, i.e. methanoic acid, ethanoic acid, benzoic acid and 4-nitrophenol, were carried out in aqueous systems by using polycrystalline TiO2 powders doped with various transition metal ions (Co, Cr, Cu, Fe, Mo, V and W). The Co-doped powder showed to be more photoactive than the bare TiO2 for methanoic acid degradation while the behaviour of TiO2/Cu and TiO2/Fe was similar to that of the support. TiO2/W was the most efficient sample for the photodegradation of benzoic acid and 4-nitrophenol, TiO2 the most active powder for ethanoic acid. A tentative explanation is provided by taking into account: (i) the dissociation constants (Ka) of the different acids used as substrates; (ii) their aliphatic or aromatic nature; (iii) the points of zero charge (PZC) of the photocatalysts; (iv) their relative rate constants for photoelectron–hole recombination (kr) determined by femtosecond pump-probe diffuse reflectance spectroscopy.


Journal of Photochemistry and Photobiology A-chemistry | 2003

Heterogeneous photocatalytic degradation of nitrophenols

A. Di Paola; Vincenzo Augugliaro; Leonardo Palmisano; G. Pantaleo; E. Savinov

The photocatalytic degradation of 2-, 3- and 4-nitrophenol has been investigated in oxygenated aqueous suspensions containing TiO2. The organic reaction intermediates have been determined by high performance liquid chromatography. The results indicate the complete mineralisation of the substrates and the formation of both nitrate and ammonium ions. The degradation pathways involve a rapid opening of the aromatic ring followed by a slower oxidation of the aliphatic compounds. The hydroxyl radicals are responsible for the primary attack of the nitrophenols with formation of dihydroxynitrobenzenes. The ring hydroxylation occurs in the positions activated by the contemporaneous presence of phenolic and nitro groups. The presence of ammonium ions confirms that reduction pathways are also operating.


Electrochimica Acta | 1981

Semiconducting properties of anodic WO3 amorphous films

F. Di Quarto; A. Di Paola; Carmelo Sunseri

Abstract The semiconducting properties of amorphous WO3 anodic films grown in different solutions and at different current densities have been investigated. The Mott—Schottky plots have shown that the donor density, Nd, of the grown films is strongly dependent on the films thickness and is not influenced by the nature of the anodizing solutions. The possible influence of the kinetics of anodization on Nd is discussed. The intersection voltages at 1/C2sc = 0 in the Mott—Schottky plots show a complex dependence on the film thickness. The possibility of obtaining the flat band potential from these plots is also discussed. A linear relationship between the square of the photocurrent and the electrode potential has been observed as previously reported for single crystals. The dissolution rate of anodic WO3 films is increased under illumination and strongly decreased in presence of Fe 2+ 3+ couple. The kinetics of electron transfer between the amorphous WO3 anodic films and the Fe 2+ 3+ redox couple in the electrolyte seems to occur in accordance with the theory developed for single crystal semiconductors.


Journal of Hazardous Materials | 2010

Photocatalytic activity of TiO2/SiO2 systems.

Marianna Bellardita; Maurizio Addamo; A. Di Paola; Giuseppe Marci; Leonardo Palmisano; L. Cassar; M. Borsa

Silica-supported TiO(2) powders were synthesized by a wet method under mild conditions. The aim of the work was the preparation of TiO(2)/SiO(2) additives for photocatalytic cements. Three types of commercial SiO(2) were used as supports: Cabot, Axim and Fly Ash. Cabot silica was ultra-pure whereas the other two silica contained different percentages of various oxides. The TiO(2)/SiO(2) samples, denoted TiO(2)/Cabot, TiO(2)/Axim and TiO(2)/Fly Ash, were prepared by boiling suspensions obtained by addition of silica to a solution of TiCl(4) in water (volume ratio 1:10). The photocatalytic activity was evaluated in a gas-solid system both in batch and in continuous reactors using 2-propanol as probe molecule. SEM-EDX analysis revealed that titanium dioxide was quantitatively deposited on silica. TiO(2)/Axim and TiO(2)/Fly Ash were scarcely active whereas a good photoactivity was exhibited by the TiO(2)/Cabot sample both in the batch and in the continuous system. Consequently only the last sample was tested for both NO(x) abatement and for 4-nitrophenol photodegradation in a liquid-solid system.


Catalysis Today | 2000

Photocatalytic behavior of mixed WO3/WS2 powders

A. Di Paola; Leonardo Palmisano; Vincenzo Augugliaro

Polycrystalline mixed WO3/WS2 powders have been prepared by different methods. The samples have been characterized by bulk and surface techniques and tested as catalysts for the photodegradation of phenol. The results have indicated that the coupling of WO3 and WS2 leads to an enhanced rate of disappearance of the organic substrate. The effect is explained as the result of the simultaneous electron transfer from WS2 to WO3 and hole transfer from WO3 to WS2. The efficiency of the mixed WO3/WS2 systems strongly depends on the relative amounts of WO3 and WS2 in the various samples. A maximum of photoactivity is obtained when the surface WS2 and WO3 molar fraction is about 0.5.


Journal of The Electrochemical Society | 1987

A Photocurrent Spectroscopic Investigation of Passive Films on Ferritic Stainless Steels

Carmelo Sunseri; S. Piazza; A. Di Paola; F. Di Quarto

Etude experimentale de la nature des films passifs croissant sur trois aciers inoxydables ferritiques de compositions differentes immerges dans une solution a 3,5% NaCl a la temperature ambiante


International Journal of Photoenergy | 2001

Transition metal doped TiO2: physical properties and photocatalytic behaviour

A. Di Paola; Shigeru Ikeda; Giuseppe Marci; Bunsho Ohtani; Leonardo Palmisano

Two probe photocatalytic reactions, i.e. ethanoic acid and 4-nitrophenol photooxidation, were carried out in different experimental conditions by using suspensions of transition metal (Co, Cr, Cu, Fe, Mo, V and W) doped polycrystalline TiO2 powders in aqueous systems. A beneficial influence of the pres- ence of metal species was observed only with the samples containing copper and tungsten. In particular, the TiO2/Cu powders showed to be more photoactive of bare TiO2 for the ethanoic acid oxidation while the TiO2/W samples were more efficient for 4-nitrophenol degradation. A tentative interpretation is provided on the basis of the values of the points of zero charge of the powders and of the rate constants of recombi- nation of photogenerated electrons and holes, determined by femtosecond pump-probe diffuse reflectance spectroscopy (PP-DRS).


Journal of The Electrochemical Society | 1980

Kinetics of Growth of Amorphous WO 3 Anodic Films on Tungsten

F. Di Quarto; A. Di Paola; Carmelo Sunseri

The kinetics of growth of anodic films have been studied in 0.01Nsolutions of , , , and at room temperature. The validity of the relationship was verified in the current density range 0.2–16 mAcm−2, Nearly constant B values were found in all investigated solutions. A lower value of dielectric constant was measured for the anodic films grown in phosphoric acid solutions. The effect of phosphate ions incorporation on the breakdown voltage is also discussed. The hypothesis of growth in presence of high space charge is carefully considered.


Corrosion Science | 1980

Anodic oxide films on tungsten—I. The influence of anodizing parameters on charging curves and film composition

A. Di Paola; F. Di Quarto; Carmelo Sunseri

Abstract The formation of anodic films on tungsten has been studied in 1N solutions of H 2 PO 4 , H 2 SO 4 , HNO 3 , HClO 4 and HCl at different temperatures. The shape of the anodic charging curves depends on the electrolyte composition and on the temperature. The chemical composition of the films is strongly influenced by the working temperature. The first step of the anodization is the formation of a barrier film of amorphous WO 3 . The thickening of the oxide layer occurs on account of the WO 3 dissolution and following precipitation of sparingly soluble oxides on the electrode surface.


Solar Energy Materials | 1985

Influence of thermal treatment on the photoelectrochemical behaviour of WO3 photoanodes electrochemically grown

F. Di Quarto; A. Di Paola; S. Piazza; Carmelo Sunseri

Abstract The influence of anodizing parameters and thermal treatments on the photoelectrochemical behaviour of the corrosion layers grown on tungsten is presented and discussed. Very significant changes are observed in the photocurrent spectra as well as in the photocharacteristics of anodic oxide films grown in different conditions. Large increases in the measured photocurrent and in the resistance against photocorrosion are observed after thermal treatment. An explanation of these findings is suggested according to the experimental results. The influence of morphology, composition and crystallographic structure on the photoelectrochemical behaviour of different tungsten oxide photoanodes is presented and discussed by taking into account possible changes in the solid-state properties of the films. The possible formation of defective structures during a long-term photoelectrolysis experiment is also discussed.

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