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Photocatalytic water splitting has great potential in solar-hydrogen production as a low-cost and environmentally friendly method. Different unique techniques used to obtain photocatalysts with various modifications to improve H2 generation have been introduced. In the present work, SrTiO3 was successfully synthesized via the solvothermal method in the presence of ionic liquid (IL) - 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) followed by surface decoration with Pt particles using the photodeposition method. The effect of the noble metal content and presence of IL on the morphology, optical and surface properties of SrTiO3, thereby the effectiveness of hydrogen generation, has been thoroughly examined and presented. Unexpectedly, the presence of [BMIM][Br] at the SrTiO3 surface affected the interaction between the semiconductor surface and platinum particles formed throughout photodeposition. Platinum particles at the surface of SrTiO3_IL were found to be in the form of 2D clusters with a size of 1 nm. In comparison, Pt deposited on SrTiO3 photocatalyst without application of IL created larger, three-dimensional structures with a diameter exceeding 5 nm. This is the reason why the total amount of platinum deposited on the SrTiO3_IL sample is smaller than that on SrTiO3 and justifies a higher efficiency of hydrogen generation of Pt modified SrTiO3 photocatalyst in comparison to SrTiO3 prepared in the presence of IL. The mechanism of H2 generation in the water-splitting reaction in the presence of SrTiO3_Pt photocatalyst was discussed.

The importance of coupled clusters iterative triple and noniterative quadruple, T(Q), electron excitations on the potential energy surfaces (PESs) of van der Waals molecules is examined for H2���CO. The evaluation of this importance is performed by comparing theoretical spectra with experiment. Somewhat surprisingly, although the T(Q) contributions to interaction energies are below 3%, the inclusion of them reduces the error of theory with respect to experiment by an order of magnitude and qualitative agreement of the spectra in some regions is achieved only when they are included. The main reason for these observations is that the T(Q) effects significantly change the anisotropy of the PES.

The design of an active, stable and efficient photocatalyst that is able to be used for hydrogen production is of great interest nowadays. Therefore, four methods of AgTaO3 perovskite synthesis, such as hydrothermal, solvothermal, sol-gel and solid state reactions, were proposed in this study to identify the one with the highest hydrogen generation efficiency by the water splitting reaction. The comprehensive results clearly show that the solid state reaction (SSR) led to the obtainment of a sample with an almost seven times higher photocatalytic activity than the other methods. Furthermore, four ionic liquids, all possessing nitrogen in the form of organic cations (two imidazoliums with different anions, ammonium and tetrazolium), were used for the first time to prepare composites consisting of AgTaO3 modified with IL and Pt, simultaneously. The effect of the ionic liquids (ILs) and Pt nanoparticles&rsquo, presence on the structure, morphology, optical properties, elemental composition and the effectiveness of the hydrogen generation was investigated and discussed. The morphology investigation revealed that the AgTaO3 photocatalysts with the application of [OMIM]-cation based ILs created smaller granules (&lt, 500 nm), whereas [TBA] [Cl] and [TPTZ] [Cl] ILs caused the formation of larger particles (up to 2 &mu, m). We found that various ILs used for the synthesis did not improve the photocatalytic activity of the obtained samples in comparison with pristine AgTaO3. It was detected that the compound with the highest ability for hydrogen generation under UV-Vis irradiation was the AgTaO3_0.2% Pt (248.5 &mu, mol∙g&minus, 1), having an almost 13 times higher efficiency in comparison with the non-modified pristine sample. It is evidenced that the enhanced photocatalytic activity of modified composites originated mainly from the presence of the platinum particles. The mechanism of photocatalytic H2 production under UV-Vis light irradiation in the presence of an AgTaO3_IL_Pt composite in the water splitting reaction was also proposed.

Silver phosphate (Ag3PO4) could be considered as visible light induced photocatalyst for pollutants degradation, due to its narrow band gap (∼2.4 eV). However, Ag3PO4 photoactivity depends on surface properties and synthesis route. In this study, differently shaped Ag3PO4 photocatalysts have been synthesized through the precipitation, ion exchange, soft-chemical or hydrothermal method. To correlate surface properties with photoactivity all samples were characterized towards morphology, crystal structure, specific surface area, optical properties, chemical composition and activity in phenol degradation upon visible light irradiation (λ > 420 and 455 nm). It is worthwhile noting that the most active Ag3PO4 samples possessed almost the same activity in phenol degradation upon irradiation from visible range (λ > 455 nm) that P25 TiO2 upon UV light. Phenol degradation rate equaled to 3.31 and 3.23 μmol/dm3/min in the presence of branched and rhombic dodecahedral Ag3PO4 particles, while it reached 3.36 μmol/dm3/min in the presence of P25 and UV light. Analysis of the degradation intermediates indicated that the benzoquinone was the primary byproducts of phenol degradation. Scavengers-assisted photocatalytic test confirmed that mainly O2− has been involved in phenol degradation under visible radiation. Surface composition analysis by XPS suggested that higher total silver content favors photoactivity, while higher ratio of Ag0 to Ag+ suppress photoactivity. Long term photocatalytic tests also implies that increase in Ag0 amount at the Ag3PO4 surface, due to photoreduction of Ag ions, rusulted in activity drop.

A series of binary TiO2/SrTiO3 and ternary TiO2/SrTiO3_BiOI composites have been synthesized using multistep preparation method. Characterization of the obtained photocatalysts covered complex analysis including morphology + y (SEM), BET specific surface area, porosity, optical properties (DRS), chemical composition of surface (XPS), crystal structure and crystal size (XRD). UV–vis and Vis ligh induced photocatalytic activity was investigated in the model reaction of phenol degradation in the aqueous phase. The powder TiO2/SrTiO3_BiOI ternary composites exhibited a new photocatalytic properties and could be used in the heterogeneous photocatalysis processes. The photocatalytic activity observed in the phenol degradation reaction significantly increased under the visible light range irradiation. The best photocatalytic activity was observed for the TiO2/SrTiO3_BiOI_4 sample, about 30.2 % of phenol was decomposed after 1 h of visible light irradiation. The utilization of the nanolayered materials facilitates the separation of photocatalysts from the aqueous phase. Moreover, the composite was easily reused without the significant decrease of the photocatalytic activity in three subsequent cycles. After 5 h of Vis irradiation of the isotopically labeled (1-13C) phenol solution in the presence of the TiO2/SrTiO3_BiOI_4 composite, the salicylic, maleic, fumaric and malonic acids were detected using GC–MS equipment. The identification of degradation by-products led to clarification of phenol decomposition pathway. The role of active species during the decomposition process of organic compound was investigated using different types of active species scavengers.

The effect of the ionic liquid's (IL) anion type ([BIMIM][X], where X= [Br], [PF6] or [OctSO4]) and content on the morphology, surface properties and photoactivity of TiO2 obtained by solvothermal method has been systematically investigated. Our results revealed that the presence of [Br], [OctSO4] anions favor formation of anatase phase, while presence of [PF6] anion causes formation of mixture of anatase and Ti(OH)PO4 phases. The highest photocatalytic activity under visible radiation (approximately four times higher than pristine TiO2) was observed for the TiO2 sample grown in a presence of 1-butyl-3-methylimidazolium bromide for ionic liquid to TiO2 precursor molar ratio 1:2. Visible light induced phenol degradation was found to be realized mainly by oxygen radical anions, whereas the contributions of the other processes, involving reactions with trapped electrons, holes and hydroxyl radical, are limited in the overall reaction mechanism. Quantum chemical calculations concerning model of anatase vacancy suggest that charge transfer between the bromide anion and molecular oxygen interacting with the vacancy is a source of photoreactivity induced by visible photons.

A series of TiO2/SrTiO3 and SrTiO3 microspheres decorated by Rh, Ru or Pt NPs were prepared by facile hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), photoluminescence spectrometry (PL), Fourier transform infrared (FT-IR) and Raman spectra and diffuse reflectance spectroscopy (DRS). The formation mechanism of TiO2/SrTiO3 and SrTiO3 microspheres was proposed and the photocatalytic properties of the samples were characterized using phenol as the pollutant under the UV–vis and light irradiation. The gas chromatography-mass spectrometry was employed to detect organic intermediates to establish degradation pathway of isotopically labeled (1-13C) phenol. The role of the active species in the process of the degradation was evaluated using different types of active species scavengers as well as hydroxyl radical test with coumarin were also carried out. The PL spectra indicate that the formation of TiO2/SrTiO3 and SrTiO3 decreased the recombination rate of photogenerated carriers. The obtained results revealed that the samples showed an enhanced photocatalytic activity for the degradation of organic pollutant. The SrTiO3/Rh(0.05) photocatalyst showed a higher photodegradation rate under UV–vis and Vis light (3.6 and 1.2 μmol dm−3 min−1, respectively) compared to the unmodified SrTiO3 (0.6 and 0.2 μmol dm−3 min−1, respectively). The active species trapping experiments indicated that under UV–vis as well as Vis illumination O 2 - are the main active species in the degradation process. The main by-products detected in phenol oxidation were catechol, hydroquinone, malonic, fumaric and maleic acid. Moreover, GC–MS results indicated the formation of isotopically labeled and unlabeled maleic acid which could be generated by two different pathways: trough decomposition of catechol and hydroquinone at the same time.

Most efforts in heterogeneous photocatalysis are focused on development of new and stable photoactive materials efficient in degradation of various pollutants under visible-light irradiation. In this regard, the wide-bandgap perovskite semiconductors, i.e., SrTiO3 (titanate), SrSnO3 (stannate) and AgTaO3 (tantalate), were prepared by a solvothermal method, and then modified with carbon quantum dots (CQDs) or graphene quantum dots (GQDs) co-modified with erbium. The photocactivity was investigated for: (i) toluene degradation (gas phase), (ii) phenol decomposition (aqueous phase), and (iii) inactivation of Escherichia coli K12 bacteria. It has been found that the morphology of semiconductors depends on the synthesis conditions, resulting in the formation of spherical particles, rods and faceted particles for SrTiO3, SnSrO3 and AgTaO3, respectively. Additionally, deposition of CQDs and GQDs/erbium has resulted in an enhancement of light harvesting, thus improved photoactivity under visible-light irradiation. Samples modified with both erbium and GQDs revealed much higher photoactivity than corresponding pristine and CQDs-modified samples. Moreover, all photocatalyst modified with GQDs and Er exhibited a significant antibacterial properties under visible light irradiation (λ > 420 nm). Accordingly, it has been proposed that obtained semiconductors modified with QDs and Er are promising candidates as sustainable, clean and cheap materials for environmental purification under solar radiation.

A novel synthesis process was used to prepare TiO 2 microspheres, TiO 2 P-25, SrTiO 3 and KTaO 3 decorated by CdTe QDs and/or Pt NPs. The effect of semiconductor matrix, presence of CdTe QDs and/or Pt NPs on the semiconductor surface as well as deposition technique of Pt NPs (photodeposition or radiolysis) on the photocatalytic activity were investigated. The as-prepared samples were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), photoluminescence spectrometry (PL), Fourier transform infrared (FT-IR) and Raman spectra, diffuse reflectance spectroscopy (DRS) and BET surface area analysis. The photocatalytic decomposition of toluene in gas phase, activated by light-emitting diodes (LEDs), with the CdTe/Pt nanoparticles-modified TiO 2 microspheres, P25, SrTiO 3 and KTaO 3 semiconductors was investigated under UV–vis and visible irradiation.The results showed that the photoactivity depends on semiconductor matrix. The highest photoactivity under Vis light was observed for KTaO 3 /CdTe-Pt (R) sample (56% of toluene was decompose after 30 min of irradiation). The efficiency of the most active sample was 3 times higher than result for P25 and two times higher than for unmodified KTaO 3 .

Decahedral TiO 2 decorated with bimetallic nanoparticles were synthesized via radiolysis and photodeposition method. The effect of bimetallic surface composition (Ag_Pt, Ag_Au, Au_Pd, Au_Pt) as well as deposition technique (simultaneous or sequential) on the photocatalytic activity in phenol degradation and efficiency of hydroxyl radicals generation under UV–vis light irradiation were investigated. Modified and pristine decahedral TiO 2 anatase with exposed {001} were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS). The gas chromatography-mass spectrometry was employed to detect organic intermediates to establish degradation pathway of isotopically labeled (1- 13 C) phenol. The modification with Pt and Ag nanoparticles induced an increase in photocatalytic activity of phenol degradation under UV–vis light irradiation (79% of phenol was degraded after 90 min of irradiation). The main by-products detected in phenol oxidation were catechol, hydroquinone, malonic, fumaric and maleic acid. The results indicated the formation of isotopically labeled and unlabeled maleic acid. It was noticed that all samples sequentially photodeposited on TiO 2 surface exhibited higher OH radicals generation compared to pristine TiO 2 . Our results suggest that synergistic effects between specifically engineered TiO 2 nanocrystals and unique properties of loaded bimetallic nanoparticles can enhance the charge separation of photoinduced carriers.

In the present investigation, TiO2 microspheres were decorated by bimetallic nanoparticles (Ag/Au, Ag/Pt, Ag/Pd, Au/Pt, Au/Pd and Pt/Pd) induced by photodeposition method to improve its photocatalytic activity. The prepared samples were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopic (XPS), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM-EDX) and inductively coupled plasma-mass spectrometry (ICP-MS). The photocatalytic activity of obtained samples was investigated in phenol degradation process under UV–vis and Vis light irradiation (λ > 420 nm). The highest photoactivity under UV–vis light was observed for Au/Pt_TiO2 and Pt/Pd_TiO2 photocatalysts (1.1 μmol dm−3 min−1) and under Vis for Ag/Pt_TiO2 (0.29 μmol dm−3 min−1). Obtained results indicated that direct electron transfer from the conduction band of TiO2 to the BNPs is responsible for photoactivity under UV–vis light during the phenol degradation process.

Composite photocatalysts that consist of TiO 2 and noble metal nanostructures have been considered to be the promising and pivotal material for accessible enhancement of the efficiency in the photocatalytic process carried out in the aqueous and gas phases. In this work we fabricated porous TiO 2 microspheres through a hydrothermal process followed by photochemical reduction of noble metal nanoparticles at the TiO 2 surface. The morphology and structure of M-TiO 2 spheres (M = Ag, Au, Pt and Pd) were studied with the use of various techniques, including transmission electron microscopy (TEM), X-ray powder diffraction analysis (XRD), photoluminescence (PL) and UV–vis diffuse-reflectance spectroscopy (DRS). The effect of metal amount (from 0.1 to 1 wt.%.) on the photocatalytic activity during toluene degradation in gas phase and phenol degradation in aqueous phase was investigated. Additionally, the photocatalytic activity of the M-TiO 2 samples was evaluated by measuring the formation rate of photo-induced hydroxyl radicals ( OH) under UV–vis light irradiation using coumarin as a probe. The obtained results indicated that toluene could be mostly removed from the air over TiO 2 microspheres modified with Ag, Au, Pt, and Pd nanoparticles. UV-mediated photoreactivity was almost similar for all samples obtained by loading metals from solutions consisting of 0.1 and 1 wt.% of metal precursors. Under visible light, except for Au, in gas phase toluene oxidation, the optimized loading of the metals was 0.1 wt.-% (photoreactivity changed in order: Ag-TiO 2 ≈ Pd-TiO 2 > Pt-TiO 2 >> Au-TiO 2 ). In case of phenol degradation in the aqueous phase, in the presence of UV irradiation the highest amount of metal (1.5 wt.%) was profitable, while under the Vis light reaction the medium amount of metal (0.5 wt.%) was beneficial. Additionally, it was noticed that phenol was degraded not only via oxidation by OH radicals but probably also in direct reaction with the photogenerated carriers (e − /h + ), particulary in the presence of TiO 2 spheres loaded with Au and Ag nanoparticles.

Perovskite-type oxides are a class of compounds with the general formula ABO 3 . They are a very important family of materials and exhibit properties suitable for numerous applications. In this review, the preparation, characterization, and application of selected perovskite oxides such as SrTiO 3 , KTaO 3 , NaTaO 3 , KNbO 3 , and NaNbO 3 in photocatalysis are described. In addition, various strategies for enhancing their photocatalytic activities are discussed, including doping with metals and nonmetals (Cr, Ni, Mn, Pb, Bi, N, Br, S, C, and F), modification with noble metal (Au, Ag, Pt, Pd, Ph, Ru) nanoparticles, and doping with rare earth elements (La). Moreover, the review summarizes the influence of different morphologies and surface properties on the photoactivity of the materials.

Nanoparticles composed of two different metal elements show novel electronic, optical, catalytic or photocatalytic properties from monometallic nanoparticles. Bimetallic nanoparticles could show not only the combination of the properties related to the presence of two individual metals, but also new properties due to a synergy between two metals. The structure of bimetallic nanoparticles can be oriented in random alloy, alloy with an intermetallic compound, cluster-in-cluster or core-shell structures and is strictly dependent on the relative strengths of metal-metal bond, surface energies of bulk elements, relative atomic sizes, preparation method and conditions, etc. In this review, selected properties, such as structure, optical, catalytic and photocatalytic of noble metals-based bimetallic nanoparticles, are discussed together with preparation routes. The effects of preparation method conditions as well as metal properties on the final structure of bimetallic nanoparticles (from alloy to core-shell structure) are followed. The role of bimetallic nanoparticles in heterogeneous catalysis and photocatalysis are discussed. Furthermore, structure and optical characteristics of bimetallic nanoparticles are described in relation to the some features of monometallic NPs. Such a complex approach allows to systematize knowledge and to identify the future direction of research.

Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction times (3, 6, 12, and 24 h). The properties of the prepared photocatalysts were investigated by means of UV-VIS diffuse-reflectance spectroscopy (DRS), Brunauer&ndash, Emmett&ndash, Teller (BET) surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of the phenol degradation was related to the time of the solvothermal synthesis, as determined for the TiO2_EAN(1:1)_24h sample. The microparticles of TiO2_EAN(1:1)_3h that formed during only 3 h of the synthesis time revealed a really high photoactivity under visible irradiation (75%). This value increased to 80% and 82% after 12 h and 24 h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area, thus the poresize as well as the ability to absorb UV-VIS irradiation. The high efficiency of the phenol degradation of the ionic liquid (IL)&ndash, TiO2 photocatalysts was ascribed to the interaction between the surface of the TiO2 and ionic liquid components (carbon and nitrogen).

Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction time (3, 6, 12 and 24h). The properties of the prepared photocatalysts were investigated by means of UV-vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of phenol degradation was related with a time of the solvothermal synthesis as determined for TiO2_EAN(1:1)_24h sample. Microparticles of TiO2_EAN(1:1)_3h formed during the only 3h of synthesis time revealed really high photoactivity under visible irradiation – 75%. This value increased to 80% and 82% after 12h and 24h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area thus pores size, as well as ability to absorb UV-vis irradiation. The high efficiency of phenol degradation of IL-TiO2 photocatalysts was ascribed to the interaction between the surface of TiO2 and ionic liquid components (carbon and nitrogen).

Pt, Pd, Ag and Au nanoparticles were photodeposited on the {0 0 1} crystal facets of the TiO2 anatase nanosheets. Morphological and surface characterization of the samples as well as photocatalytic activity were studied. The influence of metal precursor concentration used during photodeposition (0.05−0.5%) on size of formed metal nanoparticles together with UV and vis-mediated activity of Pt, Pd, Ag or Au−TiO2 was investigated. Generally, samples obtained by photodeposition of noble metal nanoparticles using their 0.2% precursor solutions revealed highest activity in phenol degradation reaction under visible light (λ > 420 nm). The photoactivity of the as-prepared samples with respect to the modified metal species was ordered Ag≅Pd > Au > Pt. TEM analysis showed that photodeposited metal nanoparticles appeared only on {0 0 1} facets of TiO2. The average degradation rate of phenol in the presence of Pd and Ag−TiO2 was 0.5 μmol dm−3 min−1 after 60 min of irradiation under visible light, and was five times higher than that of pure TiO2 nanosheets.

Efficient and stable photocatalysts must satisfy some critical requirements: (1) the semiconductor must have a bandgap large enough to provide energetic electrons, but small enough to allow for efficient absorption overlap with the solar spectrum (1.23 eV ≤ E g ≤ 3.0 eV, typically E g > 2.0 eV); (2) there must be a mechanism to efficiently drive the charge separation and transportation processes. From this viewpoint, it is important to obtain photocatalysts with high photoefficiency. This chapter describes the synthetic methods of unitary metal oxide semiconductors (TiO 2 , WO 3 , ZnO, Fe 3 O 3 , Ta 2 O 5 , and CuO), heterojunction photocatalysts, and composite-based materials. Their structure, surface properties, and photocatalytic activity are also discussed.

A series of novel BiyXz-TiO2/SrTiO3 composites were prepared by multistep synthesis route. The as-prepared photocatalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR), Raman spectra and BET analysis. The photocatalytic activity test was performed in aqueous solution of phenol under the irradiation of visible light range (λ ≥ 420 nm). Obtained results revealed that the BiOI_TiO2/SrTiO3 sample exhibit the highest photocatalytic activity under visible irradiation (0.6 μmol/dm3/min). Thus, it was demonstrated that modification of the TiO2/SrTiO3 microspheres by flowers-like structure made of bismuth oxyiodide resulted in enhancement of photocatalytic activity under visible light. The role of active species during the decomposition process of organic compound was investigated using different types of active species scavengers as well as electron paramagnetic resonance analysis (EPR). The study showed that in the BiOI_TiO2/SrTiO3/Vis system the holes (h+) plays relevant role in phenol decomposition. Furthermore, the stability and recyclable properties of obtained BiOI_TiO2/SrTiO3 sample were confirmed during three consecutive processes.

Because of the tremendous structural diversity of ionic liquids (ILs), simple transfer of observations performed for one IL used for IL-TiO2 preparation on different samples is not possible. Therefore, four ionic liquids, all containing distinct nitrogen-bearing organic cations (pyridinium, pyrrolidinium, ammonium, imidazolium), were used for the first time for the preparation of IL-TiO2 composites. The role of the individual IL cation in the synthesis of TiO2 microspheres, as well as the effect of the IL structure on the mechanism of the visible-light (Vis)-induced photoactivity of IL-TiO2 was presented and discussed in regard to structure, morphology, absorption properties, elemental composition, and reactive species involved in the photocatalytic reaction of phenol degradation. The successful modification of the TiO2 with organic IL species including possible interactions between IL and TiO2 surface, as well as the TiO2 matrix (doping with N), were confirmed. The sample that exhibited the highest photo...

Concrete as one of the most common building material, exposed to groundwater, soil and seawater is often object to sulphate attack. Partial replacement of Portland cement by natural zeolite has been proven to be effective in reducing sulphate attack. The results of cement sulphate resistance after 52 weeks in Na2SO4 solution are presented. The sulphate resistance of mortars was examined by determination of linear changes of specimens immersed in Na2SO4 solution. The studies of microstructure of cement mortars were carried out by scanning electron microscope equipped with energy dispersive spectrometer (EDS). Investigation includes also pictures of samples after 32 weeks exposition in corrosion solution.

As an important metal oxide, titanium dioxide has been widely investigated because of its unique surface, electronic, and photocatalytic properties, which make this material applicable in many areas of science and technology ranging from adsorption, catalysis and photocatalysis to biomedicine, environmental monitoring and cleanup, energy conversion and storage, etc. The properties of anatase TiO 2 crystals are largely determined by external surfaces exposed. Since the breakthrough in synthesizing anatase TiO 2 single crystals with a large percentage of highly reactive (0 0 1) facets in 2008, many unusual properties and applications of these (0 0 1) facets dominant in anatase TiO 2 have been explored theoretically and experimentally, showing the industrial importance of this semiconductor material. Here we review the recent progress in synthesizing by various synthetic methods and photocatalytic activity TiO 2 with exposed crystal facets with different morphologies.

The surface of commercial TiO2 compounds (P25 and ST01) has been modified with Ag nanoparticles induced by radiolysis. On P25, the Ag nanoclusters are very small (1–2 nm) and homogeneous in size while on ST01, two populations of nanoparticles are obtained, small nanoparticles (1–2 nm) and larger ones (mean diameter 7 to 12 nm depending on the silver loading). The photocatalytic properties of Ag-modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV and visible light. Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification (P25 and ST01) with Ag nanoparticles plays a role in charge-carrier separations increasing the activity under UV light. Indeed, Ag nanoparticles act as electron scavengers, decreasing the charge carrier recombination. TRMC measurements show also that more electrons are produced in the conduction band of P25 under UV illuminatio...

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. By far, titania has played a much larger role in this scenario compared to other semiconductor photocatalysts due to its costly effectiveness, inert nature and photostability. A substantial amount of research has focused on the enhancement of TiO(2) photocatalysis by modification with metal, non-metal and ion doping. This paper aims to review and summarize the recent works on the titanium dioxide (TiO(2)) photocatalytic oxidation of phenol and discusses various mechanisms of phenol photodegradation (indicating the intermediates products) and formation of OH radicals. Phenol degradation pathway in both systems, TiO(2)/UV and doped-TiO(2)/Vis, are described.

Preparation route of new tungsten-containing TiO2 powders (W-TiO2) and their activity under visible light are reported. The photocatalysts were prepared by the sol–gel method and by grinding anatase powder with a dopant precursor followed by calcinations (surface impregnation method). Tungsten oxide and tungsten hexacarbonyl were used as tungsten sources in both photocatalyst preparation procedure. The obtained photocatalysts were subsequently characterized by a BET method, X-ray photoelectron emission spectroscopy (XPS) and X-ray powder diffraction analysis (XRD). Degradation efficiency of phenol and formation of phenol degradation by-products were compared for two systems: W-doped TiO2 under visible light and P-25 under UV irradiation. The highest photoactivity under visible light was observed for 3%-W-TiO2 and it was three times higher than photoactivity of pure TiO2. Phenol oxidation in the presence of W-TiO2 and visible light leads to formation of hydroxyproduct (catechol) and phenol ring cleavage products (muconic aldehyde).

Boron-doped TiO2 was prepared by the sol-gel method and by grinding TiO2 powder with a boron compounds (boric acid and boric acid triethyl ester followed by calcinations at temperature range 200 to 600°C. Three types of pristine TiO2: ST-01 (Ishihara Sangyo Ltd., Japan; 300 m2/g), P25 (Degussa, Germany, 50 m2/g), A11 (Police S.A., Poland 12 m2/g) were used in grinding procedure. The photocatalytic activity of obtained powders in visible light was estimated by measuring the decomposition rate of phenol (0.21 mmol/dm3) in an aqueous solution. The photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), UV-VIS absorption and BET surface area measurements. The best photoactivity under visible light was observed for B-TiO2 modified with 2 wt% of boron prepared by grinding ST-01 with dopant followed by calcinations at 400°C. This photocatalyst contains 16.9 at.% of carbon and 6.6 at.% of boron in surface layer and its surface area is 192 m2/g.

Our research examines the photoactivity under visible light (λ > 400 nm) and surface properties (BET surface area, UV–vis absorption properties, chemical composition and crystal structure) of boron-modified TiO2. B–TiO2 photocatalysts were prepared by surface impregnation procedure using boric acid triethyl ester (BATE) as a boron precursor. The photocatalytic activity of obtained powders in visible light was estimated by measuring the decomposition of phenol (0.21 mmol/dm3) in aqueous solution. The effect of boron content, calcination temperature and titanium dioxide source used during preparation procedure on photoactivity was investigated. The degradation of phenol indicated that the photoactivity under visible light strongly depended on preparation manner of B–TiO2 photocatalysts. The highest photoactivity was observed for the sample obtained by impregnation with 2 wt.% of BATE and calcinated at 400 °C. Phenol degradation rate, in the presence of these samples, equaled to 3.0 μmol dm−3 min−1. The mode of BATE binding to TiO2 surface is discussed.

Synthesis of new boron-containing TiO2 powders (B-TiO2) and their activity under UV and visible light are reported. The catalysts were prepared by the sol–gel method and by grinding anatase powder with a dopant. Boric acid triethyl ester and boric acid were used as boron sources in both catalysts preparation procedures. The photocatalytic activity of obtained powders in UV and visible light was estimated by measuring the decomposition rate of phenol (0.21 mmol/dm3) in an aqueous solution. Carbon and boron presence in all prepared photocatalysts was confirmed by the XPS technique. The oxidation state of B atoms incorporated in TiO2 particles was mainly B3+, as determined from the X-ray photoelectron spectra (XPS). It was confirmed that boron-doped TiO2 was activated by visible light and used as effective catalyst in photooxidation reactions.

Geometry of the photoreactors depends mainly on the application as well as on the available irradiation source. Additionally, the following factors also need to be considered during the design of photoreactors: (1) type and particle size of the photocatalyst; (2) distribution of the photocatalyst (fixed or suspended); (3) type, content, and distribution of pollutants; (4) mass transfer; (5) fluid dynamics (laminar or turbulent flow); (6) temperature control; (7) reaction mechanism; and (8) reaction kinetics. This chapter deals with the general classification and description of photoreactors used for reaction carried out in the gas and liquid phase. Different types of photoreactors are described in relation to their applications.

The paper presents a short review of published results about different methods of waste glycerol conversion to the various chemicals and energy carriers as well the preliminary experimental results of the photocatalytic glycerol conversion into hydrogen. The first part of the paper presents literature data pertaining to the glycerol utilization, including thermal methods (incineration, pyrolysis, gasification and reforming), catalytic oxidation, chemical and biochemical conversion and photoconversion into hydrogen, are presented. The mechanism of selected processes and reaction conditions are also discussed. The second part of the paper presents the results of the hydrogen production over irradiated aqueous glycerol solution containing TiO

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. By far, titania has played a much larger role in this scenario compared to other semiconductor photocatalysts due to its costly effectiveness, inert nature and photostability. A substantial amount of research has focused on the enhancement of TiO(2) photocatalysis by modification with metal, non-metal and ion doping. This paper aims to review and summarize the recent works on the titanium dioxide (TiO(2)) photocatalytic oxidation of phenol and discusses various mechanisms of phenol photodegradation (indicating the intermediates products) and formation of OH radicals. Phenol degradation pathway in both systems, TiO(2)/UV and doped-TiO(2)/Vis, are described.

A wide range of techniques have been developed for the preparation of nanomaterials. These techniques include physical methods such as mechanical milling (Arbain et al., 2011) and inert gas condensation (Perez-Tijerina et al., 2008), along with chemical methods such as chemical reduction (Song et al., 2009), photochemical reduction (Ghosh et al., 2002), electrodeposition (Mohanty, 2011), hydrothermal (Hayashi & Hakuta, 2010), and sol-gel synthesis (Sonawane & Dongare, 2006). Among all chemical methods the microemulsion has been demonstrated as a very versatile and reproducible method that allows to control over the nanoparticle size and yields nanoparticles with a narrow size distribution (LopezQuintela, 2003).