Special Issue "Photocatalysts"

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A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (15 April 2013)

Special Issue Editors

Guest Editor
Prof. Dr. Cooper H. Langford

Chemistry, Science A 109, 731 Campus Place N.W., University of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada T2N 1N4
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Phone: 1 403 220 3228
Interests: inorganic photochemistry and element speciation in the natural environment
Guest Editor
Prof. Dr. Bunsho Ohtani

Catalysis Research Center (by September 30)/Institute for Catalysis (from October 1), Hokkaido University, Japan
Website | E-Mail
Interests: phtoocatalysis; particle chemistry; electrochemistry

Special Issue Information

Dear Colleagues,

Photocatalysis is a term that combines the basic notion of a catalyst that enhances rate without being consumed with the notion that the reaction is induced and/or accelerated by photons. Focused primarily on heterogeneous processes using “semiconductor” photocatalysts, it has evolved in three phases. The first generation (1975–1985) focused primarily on the studies providing understanding of the illuminated semiconductor/solution interface. The second phase featured work on polycrystalline thin films, doping semiconductors for visible light, dye sensitization, and exploration of the scope of photocatalysis. In the third generation period since 2000, photocatalysis research has continued to expand so that in the 2006–2010 period publications on photocatalysts exceeded those aimed at energy conversion, 16,757 to 12,811. This period has seen two fundamental principles, the special properties of the nanoscale and the power of self-organization, converge to provide a new conceptual platform on which to construct photocatalysts. At this time stimulating work is being done on problems associated with each of these phases, often combining emphases. This special issue invites significant contributions of all of these types plus contributions that show the power of homogeneous systems. It is hoped that it can catalyse communication between researchers in the hybrid area of photocatalysis and the larger catalysis community.

Prof. Dr. Cooper H. Langford
Prof. Dr. Bunsho Ohtani
Guest Editors

Submission

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Keywords

  • photocatalyst
  • TiO2
  • band gap
  • band edge
  • hole transfer
  • electron capture
  • dye sensitization
  • photocatalyst doping
  • nanoparticles
  • self-assembled
  • homogeneous photocatalysis

Published Papers (21 papers)

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Editorial

Jump to: Research, Review

Open AccessEditorial Photocatalysis—A Special Issue on a Unique Hybrid Area of Catalysis
Catalysts 2012, 2(3), 327-329; doi:10.3390/catal2030327
Received: 7 June 2012 / Revised: 26 July 2012 / Accepted: 30 July 2012 / Published: 9 August 2012
Cited by 2 | PDF Full-text (113 KB) | HTML Full-text | XML Full-text
Abstract An overview of the development of photocatalysis with an identification of contemporary areas of interest. Photocatalysis is placed in the broad field of catalysis. [...] Full article
(This article belongs to the Special Issue Photocatalysts)

Research

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Open AccessArticle Application of Photocatalysts and LED Light Sources in Drinking Water Treatment
Catalysts 2013, 3(3), 726-743; doi:10.3390/catal3030726
Received: 15 June 2013 / Revised: 20 August 2013 / Accepted: 28 August 2013 / Published: 12 September 2013
Cited by 10 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
This study investigates a cross-section of TiO2 compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a
[...] Read more.
This study investigates a cross-section of TiO2 compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a distinctly superior photocatalyst composition for drinking water treatment is now available that would shape design choices. An answer was sought by synthesizing several photocatalysts with reported high reactivity in some context in the literature, and by performing photocatalysts reactivity tests using common pollutants of water system including Natural Organic Matter (NOM) and Emerging Contaminants (ECs) from the pesticide and pharmaceutical classes. 365 nm Light Emitting Diodes (LEDs) were used as the irradiation source. Since LEDs are now available in the UV, we did not examine the TiO2 modifications that bring band gap excitation into the region beyond 400 nm. The results suggest that the choice of the photocatalyst should be best made to fit the reactor design and photocatalyst mounting constraints such as mass transport, reactive surface, and light field. No photocatalyst composition overall, superior for all classes emerged. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Photocatalytic Activity of Vis-Responsive Ag-Nanoparticles/TiO2 Composite Thin Films Fabricated by Molecular Precursor Method (MPM)
Catalysts 2013, 3(3), 625-645; doi:10.3390/catal3030625
Received: 10 May 2013 / Revised: 24 June 2013 / Accepted: 19 July 2013 / Published: 31 July 2013
Cited by 10 | PDF Full-text (1287 KB) | HTML Full-text | XML Full-text
Abstract
The Ag-nanoparticles (Ag-NP)/TiO2 composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100
[...] Read more.
The Ag-nanoparticles (Ag-NP)/TiO2 composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 nm thickness were fabricated by the MPM at 600 °C in air. The decoloration rates monitored by the absorption intensity of the MB solution indicated that the composite thin films of Ag with an amount less than 40 mol% are not effective under vis-irradiation, though they can work as a photocatalyst under UV-irradiation. Further, the UV-sensitivity of the composite thin films gradually decreased to almost half the level of that of the TiO2 thin film fabricated under the identical conditions when the Ag amount increased from 10 to 40 mol%. Contrarily, the composite thin films of Ag content larger than 50 mol% showed the vis-responsive activity, whose level was slightly lower than the decreased UV-sensitivity. Diffuse reflectance spectra suggested that the vis-responsive activity of the composite thin films is due to the conductivity, localized surface plasmon resonance and surface plasmon resonance of Ag-NP. It was also elucidated that the vis-responsive level of the composite thin films corresponds to their electrical conductivity that depends on the Ag content. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Dye Modification Effects on TaON for Photocatalytic Hydrogen Production from Water
Catalysts 2013, 3(3), 614-624; doi:10.3390/catal3030614
Received: 23 April 2013 / Revised: 26 June 2013 / Accepted: 17 July 2013 / Published: 23 July 2013
Cited by 7 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text
Abstract
Modification effects of porphyrin dyes on the photocatalytic activity of tantalum (oxy)nitride (TaON) were investigated. The nitrogen content in tantalum (oxy)nitride was increased by increasing the heat treatment period. The optimized nitridation conditions were found to be calcination at 800 °C for 14
[...] Read more.
Modification effects of porphyrin dyes on the photocatalytic activity of tantalum (oxy)nitride (TaON) were investigated. The nitrogen content in tantalum (oxy)nitride was increased by increasing the heat treatment period. The optimized nitridation conditions were found to be calcination at 800 °C for 14 h under a NH3 gas flow (25 mL min−1). Among the porphyrin dyes examined, pentamethylene bis[4-(10,15,20-triphenylporphine-5-yl) benzoate]-dizinc (II) (Zn-TPPD) showed the most positive effect on the photocatalytic activity of TaON for H2 production from Na2S aqueous solution. From the results of the photocatalytic reaction using various combinations of catalyst components, it was found that the modification dye and PtOx co-catalysts were necessary to achieving photocatalytic H2 formation. In the PtOx/Zn-TPPD/TaON photocatalyst, the expected charge transfer mechanism was a two-step excitation of both TaON and Zn-TPPD, and the oxidation and reduction sites were TaON and PtOx co-catalyst, respectively. These results indicate that dye modification has the potential to improve the photocatalytic activity of various (oxy)nitride photocatalysts. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Photocatalytic Degradation of Acridine Orange over NaBiO3 Driven by Visible Light Irradiation
Catalysts 2013, 3(2), 501-516; doi:10.3390/catal3020501
Received: 1 March 2013 / Revised: 3 May 2013 / Accepted: 10 May 2013 / Published: 21 May 2013
Cited by 2 | PDF Full-text (868 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The photocatalytic degradation of acridine orange (AO) dye by NaBiO3 photocatalyst under visible light irradiation was investigated systematically. The NaBiO3 photocatalyst exhibited a higher photocatalytic activity compared to the P25 photocatalyst. After 160 min of photocatalytic reaction, the degradation rate of
[...] Read more.
The photocatalytic degradation of acridine orange (AO) dye by NaBiO3 photocatalyst under visible light irradiation was investigated systematically. The NaBiO3 photocatalyst exhibited a higher photocatalytic activity compared to the P25 photocatalyst. After 160 min of photocatalytic reaction, the degradation rate of AO could reach to 99% in appropriate conditions. Factors, such as catalyst dosage, solution pH, initial AO concentration and the presence of anions, were found to influence the degradation rate. To scrutinize the mechanistic details of the dye photodegradation, the intermediates of the processes were separated, identified and characterized by the HPLC-ESI-MS technique. The analytical results indicated that the N-de-methylation degradation of AO dye took place in a stepwise manner to yield mono-, di-, tri- and tetra-N-de-methylated AO species generated during the processes. The probable photodegradation pathways were proposed and discussed. Full article
(This article belongs to the Special Issue Photocatalysts)
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Open AccessArticle Manganese Oxide-Surface Modified Titanium (IV) Dioxide as Environmental Catalyst
Catalysts 2013, 3(2), 444-454; doi:10.3390/catal3020444
Received: 23 December 2012 / Revised: 10 April 2013 / Accepted: 12 April 2013 / Published: 23 April 2013
Cited by 13 | PDF Full-text (2682 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study is to present an “environmental catalyst” possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnOx clusters are highly dispersed on the surface of TiO2 (anatase/rutile = 4/1 w/w
[...] Read more.
The purpose of this study is to present an “environmental catalyst” possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnOx clusters are highly dispersed on the surface of TiO2 (anatase/rutile = 4/1 w/w, P-25, Degussa) by the chemisorption-calcination cycle technique using Mn(acac)3 complex as a precursor (MnOx/TiO2). The thermo- and photo-catalytic activities of MnOx/TiO2 were studied for the degradation of 2-naphthol used as a model water pollutant. In contrast to the FeOx/TiO2 system, MnOx/TiO2 exhibits high thermocatalytic activity exceeding those of bulk β-β-MnO2 and Mn2O3. Also, visible-light activity is induced by the surface modification of TiO2 with MnOx clusters, whereas its UV-light activity decreases. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Generation of Free OHaq Radicals by Black Light Illumination of Degussa (Evonik) P25 TiO2 Aqueous Suspensions
Catalysts 2013, 3(2), 418-443; doi:10.3390/catal3020418
Received: 16 December 2012 / Revised: 23 January 2013 / Accepted: 22 March 2013 / Published: 16 April 2013
Cited by 13 | PDF Full-text (859 KB) | HTML Full-text | XML Full-text
Abstract
This work demonstrates how formation of strongly chemiluminescent 3-hydroxyphthalic hydrazide by hydroxylation of non-chemiluminescent phthalic hydrazide can be applied as a selective reaction probe to obtain information on authentic hydroxyl radical, i.e., OHaq, formation, in black light illuminated Degussa
[...] Read more.
This work demonstrates how formation of strongly chemiluminescent 3-hydroxyphthalic hydrazide by hydroxylation of non-chemiluminescent phthalic hydrazide can be applied as a selective reaction probe to obtain information on authentic hydroxyl radical, i.e., OHaq, formation, in black light illuminated Degussa P25 TiO2 aerated suspensions in the pH range from 3 to 11. The OHaq formation was found to be strongly pH dependent. At alkaline pH, the apparent quantum efficiency of OHaq formation was estimated to be at the ~10−2 level whereas at acidic pH it was near zero. Addition of phosphate and fluoride ions substantially enhanced the OHaq production in the acidic pH range. It is suggested that OHaq-radical formation in TiO2 photocatalysis can occur by oxidation of hydroxyl ions in the water layer adsorbed on TiO2 surfaces. Full article
(This article belongs to the Special Issue Photocatalysts)
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Open AccessArticle Visible Light-Photocatalytic Activity of Sulfate-Doped Titanium Dioxide Prepared by the Sol−Gel Method
Catalysts 2013, 3(2), 363-377; doi:10.3390/catal3020363
Received: 19 February 2013 / Revised: 18 March 2013 / Accepted: 21 March 2013 / Published: 8 April 2013
Cited by 5 | PDF Full-text (1683 KB) | HTML Full-text | XML Full-text
Abstract
Sulfate-doped TiO2 was prepared from sol−gel systems containing titaniumalkoxide and sulfuric acid. The time needed for gelation of the systems was significantlyreduced by ultrasonic irradiation. The doped sulfate was observed by FTIR and XPSmeasurements. Some sulfate ions remained in the TiO2 even after
[...] Read more.
Sulfate-doped TiO2 was prepared from sol−gel systems containing titaniumalkoxide and sulfuric acid. The time needed for gelation of the systems was significantlyreduced by ultrasonic irradiation. The doped sulfate was observed by FTIR and XPSmeasurements. Some sulfate ions remained in the TiO2 even after heating at 300−600 °C.The UV and visible photocatalytic activities of the samples were confirmed by thedegradation of trichloroethylene (TCE). The activity of the photocatalyst samples duringthe UV irradiation strongly depended on their crystallinities rather than their specificsurface areas, i.e., adsorption ability. The degradation rate during the visible irradiationdepended on both the adsorption ability and visible absorption of the photocatalystsamples. The visible absorption induced by the sulfate-doping was effective for theTCE degradation. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Broad Spectrum Microbicidal Activity of Photocatalysis by TiO2
Catalysts 2013, 3(1), 310-323; doi:10.3390/catal3010310
Received: 3 December 2012 / Revised: 25 January 2013 / Accepted: 6 March 2013 / Published: 21 March 2013
Cited by 16 | PDF Full-text (276 KB) | HTML Full-text | XML Full-text
Abstract
Photocatalytically active titanium dioxide (TiO2) is widely used as a self-cleaning and self-disinfecting material in many applications to keep environments biologically clean. Several studies on the inactivation of bacteria and viruses by photocatalytic reactions have also been reported; however, only few
[...] Read more.
Photocatalytically active titanium dioxide (TiO2) is widely used as a self-cleaning and self-disinfecting material in many applications to keep environments biologically clean. Several studies on the inactivation of bacteria and viruses by photocatalytic reactions have also been reported; however, only few studies evaluated the spectrum of the microbicidal activity with photocatalysis for various species. There is a need to confirm the expected effectiveness of disinfection by photocatalysis against multidrug-resistant bacteria and viruses. In this study, microbicidal activity of photocatalysis was evaluated by comparing the inactivation of various species of bacteria and viruses when their suspensions were dropped on the surface of TiO2-coated glass. Gram-positive bacteria, e.g., methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, and penicillin-resistant Streptococcus pneumoniae, were easily inactivated by photocatalysis, whereas some gram-negative bacteria, e.g., Escherichia coli and multidrug-resistant Pseudomonas aeruginosa, were gradually inactivated by photocatalysis. Influenza virus, an enveloped virus, was significantly inactivated by photocatalysis compared with feline calicivirus, a non-enveloped virus. The effectiveness of microbicidal activity by photocatalysis may depend on the surface structure. However, they are effectively inactivated by photocatalysis on the surface of TiO2-coated glass. Our data emphasize that effective cleaning and disinfection by photocatalysis in nosocomial settings prevents pathogen transmission. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Photocatalytic Oxidation Processes for Toluene Oxidation over TiO2 Catalysts
Catalysts 2013, 3(1), 219-231; doi:10.3390/catal3010219
Received: 23 November 2012 / Revised: 5 January 2013 / Accepted: 5 February 2013 / Published: 4 March 2013
Cited by 7 | PDF Full-text (396 KB) | HTML Full-text | XML Full-text
Abstract
Gas-solid heterogeneous photooxidation of toluene over TiO2 catalyst was studied to investigate the factors controlling the catalytic activities. The toluene photooxidation behavior on TiO2 was strongly affected by the formation and oxidation behavior of intermediate compounds on TiO2, and
[...] Read more.
Gas-solid heterogeneous photooxidation of toluene over TiO2 catalyst was studied to investigate the factors controlling the catalytic activities. The toluene photooxidation behavior on TiO2 was strongly affected by the formation and oxidation behavior of intermediate compounds on TiO2, and their accumulation decreased the reaction rate for toluene photooxidation. The formation and oxidation behavior of the byproduct compounds depended on the initial concentration of toluene and water vapor. In situ Fourier transform infrared (FTIR) studies revealed that water vapor promoted the cleavage of the aromatic ring and facilitated CO2 formation. At the reaction temperature of 300 K, the deposition of Pt on TiO2 suppressed CO formation, whereas catalytic activity was decreased due to the increase in the amount of intermediate compounds. On the other hand, Pt/TiO2 showed higher activity than TiO2 at 353 K, in spite of the increase of the intermediate compounds. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Inactivation of E. Coli in Water Using Photocatalytic, Nanostructured Films Synthesized by Aerosol Routes
Catalysts 2013, 3(1), 247-260; doi:10.3390/catal3010247
Received: 10 December 2012 / Revised: 13 January 2013 / Accepted: 30 January 2013 / Published: 4 March 2013
Cited by 3 | PDF Full-text (2469 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
TiO2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied
[...] Read more.
TiO2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO2 films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth’s surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Microvolume TOC Analysis as Useful Tool in the Evaluation of Lab Scale Photocatalytic Processes
Catalysts 2013, 3(1), 74-87; doi:10.3390/catal3010074
Received: 21 November 2012 / Revised: 24 December 2012 / Accepted: 16 January 2013 / Published: 22 January 2013
PDF Full-text (703 KB) | HTML Full-text | XML Full-text
Abstract
Analysis methods that require small volumes of aqueous samples can be of large benefit for applications when expensive chemicals are involved or available volumes are substantially small and concentrations are low. A new method is presented to allow microvolume liquid injections on TOC
[...] Read more.
Analysis methods that require small volumes of aqueous samples can be of large benefit for applications when expensive chemicals are involved or available volumes are substantially small and concentrations are low. A new method is presented to allow microvolume liquid injections on TOC equipment using a special designed Shimadzu gas injection kit® in combination with a high precision syringe and Chaney adapter. Next to details on the methodology of microvolume TOC injections, the technique is shown to be beneficial to evaluate the efficiency of photocatalytic dye degradation on titania materials in terms of CO2 conversion simultaneously with classic UV-Vis analysis measurements within a lab scale photocatalytic test setup (volume <100 mL). The possibility to allow multiple microvolume samplings in short time intervals during several hours without a substantial decrease in volume/catalyst ratio is of particular value for the evaluation of photocatalysts. By combining both techniques at short time intervals, additional knowledge of the degradation process/mechanism, kinetics and the efficiency can be obtained in a direct way. Moreover, the developed μV-TOC analysis is specifically useful in those applications in which low sample volumes in combination with low concentrations are involved. For example, μV-TOC can similarly be put into service in a wide range of small volume setups, e.g., analytes from high-throughput screening, pharmaceutical applications and other advanced oxidation processes that formally could not be analyzed due to limited sample volumes and often low concentrations. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessArticle Preparation and Photocatalytic Properties of Sr2−xBaxTa3O10−yNz Nanosheets
Catalysts 2013, 3(1), 1-10; doi:10.3390/catal3010001
Received: 11 November 2012 / Revised: 17 December 2012 / Accepted: 9 January 2013 / Published: 16 January 2013
Cited by 10 | PDF Full-text (462 KB) | HTML Full-text | XML Full-text
Abstract
Sr2−xBaxTa3O10yNz (x = 0.0, 0.5, 1.0) nanosheets were prepared by exfoliating layered perovskite compounds (CsSr2−xBaxTa3O10yNz). The Sr
[...] Read more.
Sr2−xBaxTa3O10yNz (x = 0.0, 0.5, 1.0) nanosheets were prepared by exfoliating layered perovskite compounds (CsSr2−xBaxTa3O10yNz). The Sr1.5Ba0.5Ta3O9.7N0.2 nanosheet showed the highest photocatalytic activity for H2 production from the water/methanol system among the Sr2−xBaxTa3O9.7N0.2 nanosheets prepared. In addition, Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet showed the photocatalytic activity for oxygen and hydrogen production from water. The ratio of hydrogen to oxygen evolved was around two. These results indicate that the Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet is a potential catalyst for photocatalytic water splitting. Full article
(This article belongs to the Special Issue Photocatalysts)
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Review

Jump to: Editorial, Research

Open AccessReview Titania Photocatalysis beyond Recombination: A Critical Review
Catalysts 2013, 3(4), 942-953; doi:10.3390/catal3040942
Received: 26 September 2013 / Revised: 23 October 2013 / Accepted: 5 November 2013 / Published: 15 November 2013
Cited by 25 | PDF Full-text (242 KB) | HTML Full-text | XML Full-text
Abstract
This short review paper shows the significance of recombination of a photoexcited electron and a hole in conduction and valence bands, respectively, of a titania photocatalyst, since recombination has not yet been fully understood and has not been evaluated adequately during the past
[...] Read more.
This short review paper shows the significance of recombination of a photoexcited electron and a hole in conduction and valence bands, respectively, of a titania photocatalyst, since recombination has not yet been fully understood and has not been evaluated adequately during the past several decades of research on heterogeneous photocatalysis. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessReview Specific Facets-Dominated Anatase TiO2: Fluorine-Mediated Synthesis and Photoactivity
Catalysts 2013, 3(2), 455-485; doi:10.3390/catal3020455
Received: 21 March 2013 / Revised: 22 April 2013 / Accepted: 6 May 2013 / Published: 16 May 2013
Cited by 36 | PDF Full-text (1358 KB) | HTML Full-text | XML Full-text
Abstract
Semiconductors crystal facet engineering has become an important strategy for properly tuning and optimizing both the physicochemical properties and the reactivity of photocatalysts. In this review, a concise survey of recent results obtained in the field of specific surface-oriented anatase TiO2 crystals
[...] Read more.
Semiconductors crystal facet engineering has become an important strategy for properly tuning and optimizing both the physicochemical properties and the reactivity of photocatalysts. In this review, a concise survey of recent results obtained in the field of specific surface-oriented anatase TiO2 crystals preparation is presented. The attention is mainly focused on the fluorine-mediated hydrothermal and/or solvothermal processes employed for the synthesis and the assembly of anatase micro/nanostructures with dominant {001} facets. Their peculiar photocatalytic properties and potential applications are also presented, with a particular focus on photocatalysis-based environmental clean up and solar energy conversion applications. Finally, the most promising results obtained in the engineering of TiO2 anatase crystal facets obtained by employing alternative, possibly more environmentally friendly methods are critically compared. Full article
(This article belongs to the Special Issue Photocatalysts)
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Open AccessReview The Influence of Surface Alumina and Silica on the Photocatalytic Degradation of Organic Pollutants
Catalysts 2013, 3(1), 338-362; doi:10.3390/catal3010338
Received: 23 November 2012 / Revised: 21 January 2013 / Accepted: 7 February 2013 / Published: 21 March 2013
Cited by 5 | PDF Full-text (865 KB) | HTML Full-text | XML Full-text
Abstract
Practical photocatalysis for degradation of organic pollutants must take into account the influence of other chemicals. Significant Al deposition on titania can occur at naturally occurring concentrations of dissolved Al. This paper reviews the author’s work on the influence of deliberately deposited hydrous
[...] Read more.
Practical photocatalysis for degradation of organic pollutants must take into account the influence of other chemicals. Significant Al deposition on titania can occur at naturally occurring concentrations of dissolved Al. This paper reviews the author’s work on the influence of deliberately deposited hydrous oxides of aluminium on the behavior of a ~130 m2 g−1 rutile TiO2, and then compares the behavior of deposited alumina with that of deposited silica. On rutile some adsorbed nitrogen is infrared-active. Alumina and silica deposited on the rutile reduce, and ultimately eliminate, this infrared-active species. They also reduce photocatalytic oxidation of both propan-2-ol and dichloroacetate ion and the photocatalytic reduction of diphenyl picryl hydrazine. The surface oxides suppress charge transfer and may also reduce reactant adsorption. Quantitative measurement of TiO2 photogreying shows that the adsorbed inorganics also reduce photogreying, attributed to the capture of photogenerated conduction band electrons by Ti4+ to form Ti3+. The influence of adsorbed phosphate on photocatalysis is briefly considered, since phosphate reduces photocatalytic disinfection. In the context of classical colloid studies, it is concluded that inorganic species in water can significantly reduce photoactivity from the levels that measured in pure water. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessReview Heterogeneous Photocatalysis: Recent Advances and Applications
Catalysts 2013, 3(1), 189-218; doi:10.3390/catal3010189
Received: 28 November 2012 / Revised: 18 December 2012 / Accepted: 25 January 2013 / Published: 1 March 2013
Cited by 116 | PDF Full-text (1729 KB) | HTML Full-text | XML Full-text
Abstract
Semiconductor heterogeneous photocatalysis, the subject of this review, is a versatile, low-cost and environmentally benign treatment technology for a host of pollutants. These may be of biological, organic and inorganic in origin within water and air. The efficient and successful application of photocatalysis
[...] Read more.
Semiconductor heterogeneous photocatalysis, the subject of this review, is a versatile, low-cost and environmentally benign treatment technology for a host of pollutants. These may be of biological, organic and inorganic in origin within water and air. The efficient and successful application of photocatalysis demands that the pollutant, the catalyst and source of illumination are in close proximity or contact with each other. The ability of advanced oxidation technology to remove low levels of persistent organic pollutants as well as microorganisms in water has been widely demonstrated and, progressively, the technology is now being commercialized in many areas of the world including developing nations. This review considers recent developments in the research and application of heterogeneous semiconductor photocatalysis for the treatment of low-level concentrations of pollutants in water and air using titanium dioxide as a “model” semiconductor. The review considers charge transport characteristics on the semiconductor surface, photocatalyst reactor design and organic degradation mechanistic pathways. The effects of photoreactor operating parameters on the photocatalytic process are discussed in addition to mineralization and disinfection kinetics. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessReview Brookite, the Least Known TiO2 Photocatalyst
Catalysts 2013, 3(1), 36-73; doi:10.3390/catal3010036
Received: 12 November 2012 / Revised: 9 January 2013 / Accepted: 10 January 2013 / Published: 18 January 2013
Cited by 80 | PDF Full-text (1949 KB) | HTML Full-text | XML Full-text
Abstract
Brookite is the least studied TiO2 photocatalyst due to the difficulties usually encountered in order to obtain it as a pure phase. In this review, a comprehensive survey of the different methods available for preparing brookite powders and films is reported. Attention
[...] Read more.
Brookite is the least studied TiO2 photocatalyst due to the difficulties usually encountered in order to obtain it as a pure phase. In this review, a comprehensive survey of the different methods available for preparing brookite powders and films is reported. Attention has been paid both to the most traditional methods, such as hydrothermal processes at high temperatures and pressures, and to environmentally benign syntheses using water soluble compounds and water as the solvent. Papers reporting the photocatalytic activity of pure and brookite-based samples have been reviewed. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessReview Photocatalytic Water Treatment by Titanium Dioxide: Recent Updates
Catalysts 2012, 2(4), 572-601; doi:10.3390/catal2040572
Received: 7 October 2012 / Revised: 7 December 2012 / Accepted: 10 December 2012 / Published: 19 December 2012
Cited by 94 | PDF Full-text (1026 KB) | HTML Full-text | XML Full-text
Abstract
Photocatalytic water treatment using nanocrystalline titanium dioxide (NTO) is a well-known advanced oxidation process (AOP) for environmental remediation. With the in situ generation of electron-hole pairs upon irradiation with light, NTO can mineralize a wide range of organic compounds into harmless end products
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Photocatalytic water treatment using nanocrystalline titanium dioxide (NTO) is a well-known advanced oxidation process (AOP) for environmental remediation. With the in situ generation of electron-hole pairs upon irradiation with light, NTO can mineralize a wide range of organic compounds into harmless end products such as carbon dioxide, water, and inorganic ions. Photocatalytic degradation kinetics of pollutants by NTO is a topic of debate and the mostly reporting Langmuir-Hinshelwood kinetics must accompanied with proper experimental evidences. Different NTO morphologies or surface treatments on NTO can increase the photocatalytic efficiency in degradation reactions. Wisely designed photocatalytic reactors can decrease energy consumption or can avoid post-separation stages in photocatalytic water treatment processes. Doping NTO with metals or non-metals can reduce the band gap of the doped catalyst, enabling light absorption in the visible region. Coupling NTO photocatalysis with other water-treatment technologies can be more beneficial, especially in large-scale treatments. This review describes recent developments in the field of photocatalytic water treatment using NTO. Full article
(This article belongs to the Special Issue Photocatalysts)
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Open AccessReview Conversion of CO2 via Visible Light Promoted Homogeneous Redox Catalysis
Catalysts 2012, 2(4), 544-571; doi:10.3390/catal2040544
Received: 27 August 2012 / Revised: 26 October 2012 / Accepted: 13 November 2012 / Published: 27 November 2012
Cited by 31 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
This review gives an overview on the principles of light-promoted homogeneous redox catalysis in terms of applications in CO2 conversion. Various chromophores and the advantages of different structures and metal centers as well as optimization strategies are discussed. All aspects of the
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This review gives an overview on the principles of light-promoted homogeneous redox catalysis in terms of applications in CO2 conversion. Various chromophores and the advantages of different structures and metal centers as well as optimization strategies are discussed. All aspects of the reduction catalyst site are restricted to CO2 conversion. An important focus of this review is the question of a replacement of the sacrificial donor which is found in most of the current publications. Furthermore, electronic parameters of supramolecular systems are reviewed with reference to the requisite of chromophores, oxidation and reduction sites. Full article
(This article belongs to the Special Issue Photocatalysts)
Open AccessReview Hydrogen Production from Semiconductor-based Photocatalysis via Water Splitting
Catalysts 2012, 2(4), 490-516; doi:10.3390/catal2040490
Received: 4 July 2012 / Revised: 30 August 2012 / Accepted: 28 September 2012 / Published: 17 October 2012
Cited by 65 | PDF Full-text (914 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water
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Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water splitting has attracted tremendous attention and has been extensively studied because of its great potential for low-cost and clean hydrogen production. This paper gives a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation. The topics covered include an introduction of hydrogen production technologies, a review of photocatalytic water splitting over titania and non-titania based photocatalysts, a discussion of the types of photocatalytic water-splitting approaches, and a conclusion for the current challenges and future prospects of photocatalytic water splitting. Based on the literatures reported here, the development of highly stable visible–light-active photocatalytic materials, and the design of efficient, low-cost photoreactor systems are the key for the advancement of solar-hydrogen production via photocatalytic water splitting in the future. Full article
(This article belongs to the Special Issue Photocatalysts)

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