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The photoelectrocatalytic (PEC) oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 was investigated by using Pt, Au and Pd loaded (as single or bimetallic) nanotube structured TiO2 on Ti plate in water under UVA irradiation. Nanotube structured TiO2 on Ti plate samples were prepared as anode by anodic oxidation method in ethylene glycol solution in different times, and then they were calcined at 500 °C to be obtained in crystalline form. The anodes were loaded with noble metals by electrochemical reduction method and characterized by XRD, XPS, SEM, and photocurrent techniques. The TiO2 on the plates was in the anatase phase. The loaded metals were in metallic form and heterogeneously dispersed on the TiO2 surface in different sizes. The results indicate that a high amount of metal loading negatively affected the PEC activity of the metal loaded samples because UVA irradiation inside the nanotubes was inhibited by the presence of the metal. On the contrary, low amount of Pd showed high PEC activity and high product selectivity values with respect to the pristine sample. PEC experiments were also more selective than the photocatalytic ones for vitamin B3 production. Electrocatalytic (EC) and photocatalytic (PC) experiments were also conducted, however no or low activity was obtained, respectively. PEC experiments showed to be more selective than the PC ones for vitamin B3 production.

The aim of the chapter is to describe some different preparation methods and characterization techniques for bare, supported, and coupled TiO2 samples used in different fields. Particular attention has been paid both to the fundamental aspects of the different TiO2 preparation and characterization methods and the practical applications that the results obtained can have. Various examples have been reported from the literature to demonstrate the usefulness that students and scientists working with TiO2-based materials in different research areas can derive from various characterizations.

An important factor that governs solar energy transformation into electrical or chemical energy, when using nanoparticles-based devices, is the spatial location of traps limiting electron transport. Evidences have been presented indicating that the electron diffusion is strongly influenced by nanoparticle boundaries, whose characteristics depend on the particles preparation. In the present work we have studied the role of hydrated excess proton structures in the formation of anatase nanoparticles boundaries in samples prepared by TiCl4 hydrolysis at low temperature and strong acidic conditions. The samples, constituted by anatase nanocrystals but, mainly, by amorphous titania, are studied by H-1-MAS NMR, FT-IR and HRTEM. The results indicate that hydrated excess proton species, generated by solvation of bridging hydroxyls protons of highly defective anatase and/or amorphous titania chains, favor the chains bonding to anatase nanoparticles and/or their condensation at the nanoparticles surface. The chains' bonding facilitates the anatase particles aggregation producing oriented self-assemblings. The preparation conditions determine a strong condensation of amorphous titania chains and it should favor anatase transformation into rutile. (C) 2016 Elsevier B.V. All rights reserved.

This chapter reports on some characterization techniques that are commonly used for catalysts and photocatalysts. Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV–visible (UV–Vis), photoluminescence (PL), and electrochemical characterization techniques are presented with experimental details and actual case studies from literature are discussed. The chapter starts with adsorption phenomena on (photo)catalysis and adsorption isotherms are presented. Then BET analysis technique and its applications in (photo)catalysis are explained. Morphological properties (SEM), functional groups, and the interaction of substrate (and intermediates) with the catalyst under dark or under irradiation are discussed using the FTIR technique. The discussion moves on with estimation of band-gap energies and oxidation states of loaded or metal-doped catalysts (through UV–Vis), and to the identification of impurity/defects levels and the investigation of recombination mechanisms by PL. Finally, as electrochemical characterizations, linear sweep and cyclic voltammetry, chronoamperometry (photocurrent), electrochemical impedance spectroscopy, and Fermi level estimation are presented. Special attention is given to comparative assessment between catalysts and photocatalysts, for both powder and supported samples.

This chapter reports the main techniques used to synthesize powders and films of heterogeneous catalysts and photocatalysts, often used for similar processes. Traditional preparation processes of bulky (photo)catalysts including precipitation, sol–gel technique, hydrothermal or solvothermal method, solid-state reactions, and flame syntheses were briefly described. The sonochemical method and microwave irradiation technique were also considered. The syntheses of supported catalysts by different techniques, including deposition–precipitation, impregnation, and wet coating technologies were also described. Moreover, a survey is reported of methods to deposit thin films of catalysts on various supports such as deposition–precipitation, impregnation, chemical and physical vapor deposition, or electrodeposition.

Nanotube structured TiO2 on Ti surface were prepared in ethylene glycol (Ti/TiO2NTEG) medium by anodic oxidation method with different times and then the plates were calcinated at different temperatures. Non-nanotube structured Ti/TiO2, prepared by thermal oxidation method, and nanotube structured TiO2 on Ti plate in hydrogen fluoride solution were also prepared for comparison. Pt loaded Ti/TiO2NTEG photoanodes were also prepared by cyclic voltammetry method with different cycles and the optimum loaded Pt amount was determined. Photoanodes were characterized by using X-ray Diffraction (XRD), Scanning Electron Microscopy-Energy-Dispersive X-ray Analysis (SEM-EDX), and photocurrent methods. XRD analyses proved that almost all TiO2 is in anatase phase. SEM analyses show that nanotubes and Pt nanoparticles on nanotube surface are dispersed quite homogeneously. The longest nanotubes were obtained in the ethylene glycol medium and the nanotube length increased by increasing applied anodic oxidation time. In addition, a linear correlation between nanotube length and XRD peak intensity was found. Moreover, SEM-EDX and XRD analyses evidence that Pt nanoparticles on nanotube surface are metallic and in cubic structure. Photoelectrocatalytic degradation of paraquat was performed using the prepared photoanodes. Moreover, electrocatalytic and photocatalytic degradations of paraquat were also investigated for comparison, however lower activities were observed. These results evidence that the photoanodes show a significant synergy for photoelectrocatalytic activity.

Even if many aspects of three-dimensionally ordered macroporous (3DOM) titania have been extensively studied, the interplay between the amorphous and crystalline components of their skeleton wall has not attracted too much attention, although it should strongly influence the properties of these materials. In order to gain new insight on this interplay, we have studied in detail the wall structure of three 3DOM titania samples prepared by heating the 3DOM titania precursor at 673, 773, and 873 K by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, N2 adsorption/desorption, pore-size distribution, high-resolution transmission electron microscopy, and IHmagic-angle-spinning NMR. In addition, their photoreactivity toward the partial oxidation and mineralization of 4-methoxybenzyl alcohol was determined and compared with that of commercial anatase and P25 samples. The results show that when the 3DOM sample heated at 673 K, whose skeleton wall is formed by very small anatase nanoparticles covered by relatively thick layers of amorphous titania, is heated at 773 K, most amorphous titania is eliminated, leaving a very thin amorphous titania layer covering the slightly grown anatase nanoparticles. The photoreactivity results show that the sample heated at 773 K has the highest overall photoreactivity, which was lower than those of commercial anatase and P2S samples; however, its reactivity toward the alcohol partial oxidation was the highest compared with those obtained with all of the other samples. These results indicate that amorphous titania negatively affects the overall photocatalytic activity; however, its particular distribution in the 3DOM samples enhances the partial oxidation reaction.

In a previous study on commercial TiO2 nanoparticles (J. Soria et al.) we had shown that the superficial disordered layers influence their textural and reactivity features. In the present work we used well crystallized anatase particles (commercial TiO2, BDH) as support of different amounts of titania powders, prepared by TiCl4 hydrolysis and constituted by nanocrystals diluted into an amorphous matrix. The reactivity of these photocatalysts has been tested for the selective oxidation of 4-methoxybenzyl alcohol to aldehyde in aqueous suspension. The catalyst characteristics have been studied using adsorption-desorption isotherms, TEM, HRTEM, TGA, PL, DRIFT-IR, and 1H MAS-NMR spectroscopy. The results show that, though amorphous titania species hinder the photocatalyst overall reactivity, the incorporation of a low amount of those species enhances significantly the reactivity towards the partial oxidation. This effect is attributed to the fact that, during the catalyst preparation, associations between chlorine ions and hydrated excess protons structures are produced. These associations act as surfactants, separating the layer of amorphous titania chains from anatase surface so that, under catalyst irradiation, the transport of photogenerated positive charge from anatase bridging oxygens to those of the amorphous layer is favoured.

N-doped anatase/rutile photocatalysts were prepared by a sol-gel method, using TiCl4 as TiO2 precursor and urea as N-dopant source. The catalysts required a thermal treatment at temperature higher than 300 degrees C to achieve actual nitrogen doping; this treatment also allowed obtaining crystalline and hydrophobic samples. Moreover, nitrogen doping modified the surface of samples by increasing the anatase to rutile phase ratio and hydrophilicity. The catalysts were characterized by BET specific surface area, XRD, ESEM, TGA, FT-IR, DRS and XPS measurements, with particular attention to the assessment of the N-doping effect. It was found that XPS analysis should be used together with DRS and FT-IR to discriminate whether N had been incorporated in TiO2 lattice or N species had just adsorbed on the TiO2 surface. Moreover, XPS analysis could be also used for determining the crystallinity of TiO2. The photocatalytic activity of the samples was tested for the partial oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde in water under near-UV, visible, UV-visible and simulated solar light, respectively. Commercial (Degussa P25) and undoped home-prepared TiO2 anatase-rutile catalysts were also used for comparison. The results show that N-doping improves absorption of visible light by the catalysts, but the reaction rate does not increase accordingly. Selectivity was higher in the presence of poorly crystallized catalysts, whereas doping seemed to have a slightly improving effect.

Photoelectrocatalytic (PEC) synthesis of 2,5-furandicarbaldehyde (FDC) from 5-(hydroxymethyl)-2-furaldehyde (HMF) has been performed in water by using TiO2 films on Ti layer prepared by thermal annealing of Ti (Ti/TiO2) and TiO2 nanotube on Ti (Ti/TiO2NT) prepared by anodic oxidation as photoanodes. The latter ones showed better activity. In order to improve both activity and selectivity, Ti/TiO2NT was loaded with Pt by photoreduction method. 5-Formyl-2-furoic acid (FFA) was also produced by using Pt loaded Ti/TiO2NT photoanodes. The photoanodes were characterised by using XRD, SEM and XPS techniques. Allotropic phase of TiO2 photoanodes was mainly rutile, whereas trace amounts of anatase phase were found in some samples of TiO2 nanotube photoanodes. The distribution of TiO2 nanotubes on Ti are well organised. In addition, primary particle sizes of TiO2 were increased by increasing thermal treatment temperature; however primary particle sizes of TiO2 in Ti/TiO2NT are higher than that of other samples. The photoanode preparation temperature, bias and medium pH were optimised by following PEC HMF oxidation reaction. Photocatalytic and electrocatalytic HMF oxidations were also performed for comparison and negligible activities were observed. Finally efficient Pt loaded Ti/TiO2NT photoanodes were investigated for PEC selective and active FDC (selectivity up to 40%) and FFA (selectivity up to 18%) syntheses in environmental friendly conditions. (C) 2016 Elsevier B.V. All rights reserved.

It is well known that the surface of metal oxide catalysts presents, usually, non-crystalline species containing impurities and low coordinated cations, which are observed in HRTEM images as a disordered layer of amorphous phase. Despite of being these species more accessible and less stable than the crystalline catalysts components, they have been rarely considered when analysing the catalyst activity. In this work, we have studied the effect of a treatment with HCl solution at pH = 0 on the characteristics of the disordered layer in two commercial anatase TiO2 samples, using techniques such as TGA, 1H MAS-NMR and HRTEM, and by determining these sample photocatalytic activity for the 4-nitrophenol degradation in aqueous suspension. The results indicate that associations of chlorine ions in amorphous titania chains and hydrated excess protons structures interact with anatase bridging hydroxyls. This interaction, that breaks Ti-O-Ti bonds between the anatase particles and the disordered layer species, enhances the anatase hydroxyls acidity, favouring the formation of 0-radicals and eventually increasing the photocatalytic activity for 4-nitrophenol degradation under UV irradiation. (C) 2017 Elsevier B.V. All rights reserved.

The derivatives of styrene monomer, 4-chlorophenyl-4-vinylbenzyl ether (M1), 4-methoxyphenyl-4-vinylbenzyl ether (M2), 4-ethylphenyl-4-vinylbenzyl ether (M3) and 1-naphtylphenyl-4-vinylbenzyl ether (M4) were synthesized. The normal free radical polymerization of monomers in 1,4-dioxane were performed by using 2,2'-azobisisobutyronitrile as an initiator at 65 A degrees C. The monomers and their homopolymers were characterized by FT-IR, NMR and elemental analyses measurements. The thermal stability of polymers was investigated by thermogravimetric and differential scanning calorimetric analysis. Thermal degradation activation energies of the polymers were calculated by the Ozawa and Kissinger methods. In addition, photo-stability tests of the polymers under near-UV irradiation were performed.

WOS: 000274769500044, Amorphous TiO2, prepared at room temperature through a sol-gel method implementing hydrolysis of TiCl4, has been supported on graphite rods and then annealed at 673 K. In this way graphite was completely covered by a porous anatase TiO2 layer, with an external thickness of about 1 mu m, with graphite pores completely filled by the semiconductor particles. The obtained electrode was structurally characterized by SEM microscopy coupled to EDAX mapping and by Raman spectroscopy. A Pyrex annular reactor was designed in order to test the prepared electrodes for the photoelectrocatalytic degradation of 4-nitrophenol, a target pollutant dissolved in aqueous conductive solution. The continuous reactor worked in total recirculation mode and the degradation runs were carried out by applying near UV-light, bias or both energy sources. The influence of flow rate, initial 4-nitrophenol concentration and applied potential on the degradation rate was studied

WOS: 000253222200065, Hybrid sol-gel TiO2/organosilica films doped with Cu(II), Fe(II), and Fe(III) phthalocyanines are excellent photocatalysts for the oxidative degradation of organics under visible light irradiation. The films show pronounced stability with the Fe(III)Pc-doped film showing the best performance in the gas-phase mineralization of 2-propanol. The versatile chemistry of both sol-gel materials and phthalocyanines will enable large improvement in terms of performance and technical adaptability of these new photocatalytic devices for future practical application.

This special issue of Catalysis Today Journal, is dedicated to the career of Prof. Vincenzo Augugliaro, University of Palermo, Italy, in the occasion of his retirement in 2015. Prof. Vincenzo Augugliaro was Full Professor of Transport Phenomena at the University of Palermo (Italy) since 1994. He contributed to the fol- lowing research fields: chemical absorption kinetics, biochemical reactor modelling, diffusional kinetics in metallizing alloys and heterogeneous photocatalysis; in this last field he investigated on chemical kinetics of heterogeneous photocatalytic systems, modelling of heterogeneous photoreactors, radiation field in absorbing-reacting media and application of heterogeneous pho- tocatalysis to syntheses processes. He published more than 150 papers in prestigious journals and many chapters in books and is co-author of 4 patents. Prof. Augugliaro was appreciated not only for his important achievements in the field of heterogeneous photocatalysis, but also for his great effort as mentor of many master and PhD chemical engineering students. This special issue contains twenty-four original papers by researchers involved in various aspects of heterogeneous photocatalysis.

WOS: 000333493400040, Titania and materials containing titania have received considerable attention due to their technological importance in many areas. In this study, anatase crystalline titania (TiO2) coated polystyrene (PS) colloidal particles were successfully prepared in two easy steps. First, a one pot synthesis of the colloidal particles was produced via an emulsifier-free emulsion copolymerization of styrene (S) and 2-(dimethylamino)ethyl methacrylate (DMA) at pH 4.0. In the second step, the synthesized particles were coated by titania using a sol-gel process in-situ hydrolysis and a condensation reaction of titanium(IV) isopropoxide in an acidic aqueous solution. In this way, anatase crystalline titania, rather than the usual amorphous form, was obtained as a shell on the PS colloidal particles. Both the PS colloidal particles and the polystyrene/anatase titania (PS/TiO2) core/shell colloidal particles had monodisperse morphology and were characterized using SEM, Zetasizer, FTIR, XRD and TGA techniques or measurements. In addition, the photocatalytic activity of the PS/TiO2 core/shell particles was tested for the first time in an oxidation reaction, in the oxidation of 4-methoxybenzyl alcohol (MBA) with O-2 in water. Much higher selectivities of the target product, p-anisaldehyde (AA), were obtained with the PS/TiO2 core/shell particles than with a commercial anatase crystalline TiO2

Amorphous TiO2-x formed together with precursors and anatase nuclei, during TiCl4 hydrolysis at soft conditions, influences both crystal growth and phase stability. The highly defective nanoparticles of anatase grow by reaction of their basic hydroxyls with acidic ones of TiO2 precursor species. The growth of anatase crystals, however, is affected by their interactions with simultaneously formed amorphous TiO2-x which increasingly covers the particles hindering the anatase-precursor contact. The interactions among anatase and amorphous and precursor components have been studied by H-1-MAS (magic angle spinning) NMR spectroscopy. The interaction between acid and basic hydroxyls favors the formation of Ti-O-Ti bonds between' amorphous and anatase phases, increasing the agglomeration of anatase nanoparticles. These interactions destabilize anatase crystals and favor anatase-to-rutile transformation as the solution aging progresses.

Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas-solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs. (C) 2012 Elsevier B. V. All rights reserved.

WOS: 000264524200020, This work describes the preparation of microchannel structured monolithic pieces by the "ice-segregation induced self-assembly'' (ISISA) process. The monoliths exhibit a hierarchical structure composed of homogeneously mixed colloidal silica resulting from hydrolysis and condensation of an alkoxysilane precursor (e. g., TEOS) and TiO2 polycrystalline nanoparticles adsorbed onto sepiolite fibres. The combination of such a different species into a single macroporous structure provides a multifunctional material capable of water decontamination by pollutant removal from aqueous media (via adsorption on sepiolite) and subsequent elimination by UV irradiation (via photocatalytic oxidation on TiO2 nanoparticles). The performance of the resulting materials has been studied using two organic compounds often present in wastewater such as p-nitrophenol (PNP) and methylene blue (MB)., MEC [MAT2006- 02394, S- 0505/ PPQ- 0316]; CSIC [200760I009, 200660F01], This work was supported by MEC (MAT2006- 02394 Project), CM (S- 0505/ PPQ- 0316 Project) and CSIC (200760I009 and 200660F01 Projects). M. N.- S. acknowledges TPA and CSIC for an I3P postdoctoral research contract. M. C. G. acknowledges MICINN for an R& C research contract.

WOS: 000250584100025, The optical properties of photocatalytic suspensions, that is, the absorption and scattering coefficients, depend on the effective size of particle agglomerates. This work aimed to investigate if the pH and powder concentration affect the particle size and eventually the optical properties of suspensions. Aqueous suspensions of commercial TiO2 powders irradiated by monochromatic light have been optically characterized by measuring the transimitted photon flow as a function of catalyst mass and by applying an asymptotic form of the Kubelka-Munk solution of the radiative transfer equation. It was found that equal masses of catalyst at different pH and concentration values show different particle size distributions and therefore different optical properties. Moreover, the quantum yield for the photocatalytic reaction of phenol was determined for each catalyst and pH.

Photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde was performed in water organic-free solutions by using a fixed bed continuous photoreactor containing Pyrex beads on which a TiO2 home prepared photocatalyst was supported. The influence of liquid flow rate, inlet alcohol concentration and catalyst amount on the photoprocess was studied. The highest selectivity to p-anisaldehyde was about 47% being CO2, the other main oxidation product; traces of 4-methoxybenzoic acid were also detected. The radiation field inside the photoreactor has been modelled by applying the Monte Carlo method thus allowing the determination of the local volumetric rate of photon absorption (LVRPA). It was found that the radiation intensity profile sharply decreases inside the bed so that an important aliquot of the bed is not active for the photoreaction occurrence. This finding indicates that the reactivity results, obtained by measuring the concentration values of reagents and products at the exit of photoreactor, can not be used jointly with the radiation modelling ones for determining the dependence of reaction kinetics on light intensity. The Langmuir-Hinshelwood approach has been satisfactorily applied for modelling the photoreactivity results and the values of all the model parameters have been determined.