Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2012, Article ID 280297, 4 pagesdoi:10.1155/2012/280297
Editorial
Development of Visible Light-Responsive Photocatalysts
Jinlong Zhang,1 Masaya Matsuoka,2 Jae Sung Lee,3 and Shifu Chen4
1 Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road,Shanghai 200237, China
2 Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 599-8531 Osaka, Japan3 Eco-friendly Catalysis and Energy Laboratory (NRL), Department of Chemical Engineering, Pohang University of Science andTechnology (POSTECH), Pohang 790784, Republic of Korea
4 Department of Chemistry, Huaibei Coal Normal College, Anhui, Huaibei 235000, China
Correspondence should be addressed to Jinlong Zhang, [email protected]
Received 20 December 2011; Accepted 20 December 2011
Photocatalysis has received considerable attention because ofits promising applications such as in photocatalytic degra-dation of organic pollutants, photocatalytic dissociation ofwater, solar energy conversion, and disinfection. As animportant semiconductor, photocatalytic materials, titaniahas been attracting the worldwide attention due to its goodchemical stability, insolubility in water, and nontoxic, lowcost, and readily available raw materials. It has become a hottopic in photocatalysis scopes that how to expand the spectralresponse range and improve the photocatalysis quantumefficiency of photocatalysts.
Of course, the selected topics and papers are notan exhaustive representation of the area of visible light-responsive photocatalysts. Nonetheless, they represent therich and many-faceted knowledge, that we have the pleasureof sharing with the readers. We would like to thank theauthors for their excellent contributions and patience inassisting us. Finally, the fundamental work of all reviewerson these papers is also very warmly acknowledged.
This special issue contains twenty nine papers, wheretwo reviews are related to development of visible light-responsive sensitized photocatalysts. Nine papers are dealingwith the doping or codoping TiO2 photocatalysts. Six papersare regarding the composite photocatalysts. Two papersare related to modified photocatalysts by deposition ofnoble metal. Three papers are about the preparation ofphotocatalytic film. Six papers belong to the non-TiO2
photocatalysts. Finally, one paper addresses photocatalyticdegradation of pesticides in natural water.
In the paper entitled “Development of visible light-responsive sensitized photocatalysts,” D. Pei and J. Luan
present a review of studies about the visible-light-promotedphotodegradation of the contaminants and energy conver-sion with sensitized photocatalysts. Herein authors studymechanism, physical properties, synergism effect of thesensitized photocatalysts, and the method for enhancing thephotosensitized effect.
In the paper entitled “An enthusiastic glance in to thevisible responsive photocatalysts for energy production andpollutant removal with special emphasis on titania,” Z. Yaakobet al. present some of the recently published papers onvisible responsive photocatalysts. The influence of variousmetal oxides and their sulfides on energy production andpollutant removal are presented with special emphasis ontitania photocatalysts. A keen look into the photoactivitytitania for various pollutant degradation, modified titaniasystems, physical and chemical characteristics are employedat this juncture.
In the paper entitled “Photocatalytic degradation of phe-nolics by N-doped mesoporous titania under Solar radiation,”S. S. Rayalu et al. present preparation of nitrogen dopedmesoporous titania by templating method using chitosan.This biopolymer chitosan plays the dual role of acting as atemplate (which imparts mesoporosity) and precursor fornitrogen. The doping of nitrogen into TiO2 lattice and itsstate is substantiated and measured by XPS. The photocat-alytic activity of the prepared N-doped mesoporous titaniafor phenol and o-chlorophenol degradation is investigatedunder solar and artificial radiation.
In the paper entitled “Visible-light photodegradation ofdye on co-doped titania nanotubes prepared by hydrothermalsynthesis,” Chien-Te Hsieh et al. deal with preparation of
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highly porous codoped TiO2 nanotubes from a hydrothermaltreatment and investigate their photocatalytic activity tophotodecompose methylene blue (MB) in liquid phase undervisible light irradiation.
The research of A. Nishimura et al. entitled “CO2
reforming characteristics under visible light response of Cr- orAg-doped TiO2 prepared by sol-gel and dip-coating process”presents the preparation of Cr- or Ag-doped TiO2 film by sol-gel and dip-coating process and study their photocatalyticactivity for CO2 reforming under the visible light.
In the paper entitled “Photocatalytical properties andtheoretical analysis of N, Cd-codoped TiO2 synthesized bythermal decomposition method,” X. Zhao et al. present thepreparation of N, Cd-codoped TiO2 by thermal decompo-sition method. The products represented good performancein photocatalytic degradation of methyl orange. The effectof the incorporation of N and Cd on electronic structureand optical properties of TiO2 are studied by first-principlecalculations based on density functional theory (DFT).
There is also the paper by Tang et al. “Nitrogen-dopedTiO2 photocatalyst prepared by mechanochemical method:doping mechanisms and visible photoactivity of pollutantdegradation.” Nitrogen-doped TiO2 (N/TiO2) photocata-lysts are prepared using a mechanochemica1 method withraw amorphous TiO2 as precursors and various nitroge-nous compounds doses (NH4F, NH4HCO3, NH3·H2O,NH4COOCH3, and CH4N2O). Their photocatalytical activ-ities were evaluated with the degradation of p-nitrophenoland methyl orange under UV or sunlight irradiation. Thecatalysts have a strong visible light absorption which iscorresponding to doped nitrogen and consequent oxygendeficient.
In the paper entitled “Effect of electronegativity and chargebalance on the visible-light-responsive photocatalytic activity ofnonmetal doped anatase TiO2,” Y. Dai et al. investigate theorigin of visible light absorption and photocatalytic activityof nonmetal doped anatase TiO2 in details in this workbased on density functional theory calculations. Their resultsindicate that the electronegativity is of great significance inthe band structures, which determines the relative positionsof impurity states induced by the doping species, andfurther influences the optical absorption and photocatalyticactivities of doped TiO2. The effect of charge balance on theelectronic structure is also discussed, and it is found that thecharge-balance structures may be more efficient for visible-light photocatalytic activities.
In the paper entitled “Photocatalytic activity and char-acterization of carbon-modified titania for visible-light-activephotodegradation of nitrogen oxides,” C.-H. Huang et al.present the preparation of carbon-modified titania powders,which are prepared by impregnation method using a com-mercial available titania powder, Hombikat UV100, as matrixmaterial while a range of alcohols from propanol to hexanolare used as precursors of carbon sources. Rising the carbonnumber of alcoholic precursor molecule, the modified titaniashows increasing visible activities of NOx photodegradation.
In the paper entitled “One-step cohydrothermal synthesisof nitrogen-doped titanium oxide nanotubes with enhancedvisible light photocatalytic activity,” T.-C. Hsu et al. present
a kind of nitrogen-doped TiO2 nanotubes synthesized usingcommercial titania P25 as raw material by a facile P25/ureacohydrothermal method, which shows enhanced visible lightphotocatalytic activity. The nitrogen content and surfacearea, rather than the crystallinity is found to be the crucialfactors in affecting the photocatalytic efficiency of thenitrogen-doped TiO2 nanotubes.
In the paper entitled “Highly active rare-earth metalLa-doped photocatalysts: fabrication, characterization, andtheir photocatalytic activity,” S. Anandan et al. present theinvestigation of highly active La-doped TiO2 nanoparticleswith different proportion of La content for the degradationof MCP in aqueous solution. It is observed that the rateof degradation of MCP over La-doped TiO2 increases withincreasing La loading. 1.0 wt% La-doped TiO2 is found tobe the most active among all the catalysts, which shows highrelative photonic efficiencies. The effects of electron trappingby lanthanum metal ions, particle size, surface area, andsurface roughness of the photocatalysts are supposed to bethe reason for the enhanced activity.
In the paper entitled “Preparation, characterization, andphotocatalytic property of Cu2O-TiO2 nanocomposite,” M.Zhang and L. Li present a serial of Cu2O-TiO2 nanocom-posits with high visible light photocatalytic activity for thedegradation of methyl orange, which is prepared by thehomogeneous hydrolysation, followed by the solvothermalcrystallization and ethylene glycol-thermal reduction pro-cess, respectively. The prepared Cu2O-TiO2 nanocompositesexhibit higher photocatalytic activities for the decompositionof MO than the pure Cu2O and the commercial Degussa P25under visible light irradiation.
In the paper entitled “AgBr coupled TiO2: a visible het-erostructured photocatalyst for degrading dye pollutants,” Liuet al. present a series of AgBr/TiO2 photocatalysts with het-erojunction structure and high-visible-light photocatalyticactivity, which is synthesized using Ti(OC4H9)4, KBr andAgNO3 as precursors. It is found that the coupled AgBr/TiO2
shows a stable and enhanced photodegradation rate ofmethylene blue under visible light irradiation, comparedwith the noncoupled photocatalysts of AgBr, AgBr/P25 andP25. The synergetic effect of heterostructured AgBr/TiO2 isresponsible for the strongest absorption in whole UV-vislight region.
The research of Z. Liu et al. entitled “HierarchicalCuO/ZnO membranes for environmental applications underthe irradiation of visible light” studies a new kind of highactive hierarchical CuO/ZnO nanomaterial prepared usinga facile process, which has a great potential in environ-mental applications with solar visible light. This novelCuO/ZnO membrane shows improved photodegradation ofcontaminants and antibacterial activity under the irradiationof visible light. It is found that the special hierarchicalnanostructure of CuO/ZnO is in favour of enhancing lightutilization rate, enlarging specific surface and reducing therecombination of electrons and holes at the interfacialbetween CuO and ZnO, which is the reason for the highphotocatalytic activity.
In the paper entitled “Photocatalytic oxidation of gaseousisopropanol using visible-light active silver vanadates/SBA-15
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composite,” C.-M. Huang et al. present an environ-mentally friendly visible-light driven photocatalyst, silvervanadates/SBA-15, which is prepared through an incipi-ent wetness impregnation procedure with silver vanadates(SVO). All the composites loaded with various amountof SVO inherit the higher adsorption capacity and largermineralization yield than those of P25 and pure SVO, whichis resulting from a favorable crystalline phase combined withthe high intensities of Brønsted and Lewis acids.
In the paper entitled “Sol-gel-hydrothermal synthesis ofthe heterostructured TiO2/N-Bi2WO6 composite with high-visible-light and ultraviolet-light-induced photocatalytic per-formances,” Z.-H. Huang et al. present a heterostructuredTiO2/N-Bi2WO6 composite prepared by a facile sol-gel-hydrothermal method, which has a high UV and visible lightphotocatalytic performance. The TiO2/N-Bi2WO6 compos-ites exhibit much higher photocatalytic performances thanTiO2 as well as Bi2WO6, owing to the effective electron-holeseparations at the interfaces of the two semiconductors.
In the paper entitled “Preparation of TiO2-fullerenecomposites and their photocatalytic activity under visiblelight,” Ken-ichi Katsumata et al. present the preparationand characterization of TiO2-fullerene composites which areprepared by a solution process. It is found that the rutile-C60 exhibit higher activity than the rutile under visible light,resulting from the transfer of photogenerated electrons fromthe C60 to the rutile under visible light irradiation.
The research of J. J. Murcia et al. entitled “Photocatalyticethanol oxidative dehydrogenation over Pt/TiO2: effect of theaddition of blue phosphors” investigates the effect of bluephosphors on the ethanol oxidative dehydrogenation overPt/TiO2 photocatalyst. It is found that the blue phosphorsproduced an increase in the level of ethanol conversionover the Pt/TiO2 catalyst keeping at the same time the highselectivity to acetaldehyde.
In the paper entitled “Application of Pt/CdS for thephotocatalytic flue gas desulfurization,” W. Yao et al. design aphotocatalytic flue gas desulfurization technology to controlemissions of SO2 from the combustion of fossil fuels. CdSloaded with Pt are selected as the model photocatalyst forthe photocatalytic flue gas desulfurization, and the factorsinfluencing the rate of hydrogen production and ammoniasulfite solution oxidation are detected in this paper.
The research of Y.-H. Chen and K.-J. Tu entitled“Thickness dependent on photocatalytic activity of hematitethin films” obtains a result that the photocatalytic activity ofhematite films increases with the increasing film thickness,which is because the hematite film with a thicker thicknesshas a rougher surface, providing more reaction sites forphotocatalysis. In addition, the lower band gap of a hematitefilm would generate more electron-hole pairs under visible-light illumination to enhance the photocatalytic efficiency.
In the paper entitled “Photoresponse of visible light activeCM-n-TiO2, HM-n-TiO2, CM-n-Fe2O3, and CM-p-WO3
towards water splitting reaction,” Y. A. Shaban and S. U. M.Khan summarize their studies on thin film photoelectrodesof Visible light active carbon modified titanium oxides (CM-n-TiO2); Visible light active hydrogen modified n-type tita-nium oxide (HM-n-TiO2) thin films; carbon modified iron
oxides (CM-n-Fe2O3) thin films; visible light active carbonmodified p-type tungsten oxides (CM-p-WO3) thin film.
In the paper entitled “Preparation of porous F-WO3/TiO2
films with visible-light photocatalytic activity by microarcoxidation,” K.-R. Wu et al. present a kind of porous F-WO3/TiO2 (mTiO2) films prepared on titanium sheet sub-strates using microarc oxidation (MAO) technique, whichshows an enhanced photocatalytic degradation of dye underUV and visible light irradiation, owing to its high specificsurface area from the porous microstructure.
In the paper entitled “Silver orthophosphate immobi-lized on flaky layered double hydroxides as the visible-light-driven photocatalysts,” Q. Zhang et al. present a visible-light driven photocatalyst FLDH/Ag3PO4 fabricated by thecoprecipitation method. It is found that the photocatalyticactivities of Ag3PO4 immobilized on the surface of FLDHare significantly enhanced for the degradation of acid red Gunder visible light irradiation compared to bare Ag3PO4.
In the paper entitled “Photodegradation of malachite greenby nanostructured Bi2WO6 visible light induced photocatalyst,”Zhang et al. study the photodegradation of malachite greenby the Bi2WO6 photocatalyst for the first time. The effects ofthe concentration of malachite green, the pH value, and theconcentration of Bi2WO6 on the photocatalytic efficiency areinvestigated in this paper.
In the paper entitled “Synthesis, property characterization,and photocatalytic activity of novel visible light-responsivephotocatalyst Fe2BiSbO7,” J. Luan and Z. Hu present thepreparation and characterization of visible light inducedphotocatalyst Fe2BiSbO7, which is synthesized by a solid-state reaction method for the first time. It is found that theFe2BiSbO7 possesses higher photocatalytic degradation ofMB under visible light irradiation, compared with Bi2InTaO7
or pure TiO2 or N-doped TiO2. The possible photocatalyticdegradation pathway of MB over Fe2BiSbO7 is obtained inthis paper.
In the paper entitled “Sm2FeTaO7 photocatalyst for degra-dation of indigo carmine dye under solar light irradiation,” L.M. Torres-Martınez et al. study the degradation of indigocarmine dye over Sm2FeTaO7 pyrochlore-type compound,which is synthesized by using conventional solid statereaction and sol-gel method. It is found that the solar-light-induced degradation active of sol-gel photocatalyst is 8 timesto the active of solid state. When Sm2FeTaO7 is impregnatedwith CuO as cocatalyst the photocatalytic activity is increasedbecause CuO acts as electron trap decreasing electron-holepair recombination rates.
In the paper entitled “Photosensitized oxidation of 9,10-dimethylanthracene on dye-doped silica composites,” M. A.Valenzuela et al. present a series of cationic dyes, methyleneblue (MB), safranin O (SF), toluidine blue (TB), andneutral red (NR) successfully incorporated into a silicamatrix by using ultrasound irradiation during the Stoberprocess. Among these four different types of dye-doped silicacomposites, the SiO2-SF composite shows the most efficientdelivery of singlet oxygen. This result is explained in terms ofa higher dispersion of the SF on the silica matrix.
In the paper entitled “Synthesis, characterization, andevaluation of boron-doped iron oxides for the photocatalytic
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degradation of atrazine under visible light,” D. Zhu et al.investigate the photocatalytic degradation of atrazine byboron-doped iron oxides under visible light irradiation.Boron-doped goethite and hematite are successfully preparedby sol-gel method. It is found that the B-doped ironoxides shows higher atrazine degradation rate than that ofpristine iron oxides, and the B-doped goethite exhibits betterphotocatalytic activity than B-doped hematite. The bettercrystal structure, larger BET surface area, enhanced lightabsorption ability, and narrowed band-gap energy inducedby the B-doping are responsible for the high photocatalyticactivity.
In the paper entitled “Photocatalytic degradation of pesti-cides in natural water: effect of hydrogen peroxide,” N. Miguelet al. evaluate the effectiveness of photocatalytic treatmentwith titanium dioxide in the degradation of 44 organic pesti-cides analyzed systematically in the Ebro river basin (Spain).The effect of the addition of hydrogen peroxide in thistreatment is studied in this paper. It is found that the additionof hydrogen peroxide could increase the average degrada-tion of pesticides. The pesticides which are best degradedare parathion methyl, chlorpyrifos, α-endosulphan, 3,4-dichloroaniline, 4-isopropylaniline, and dicofol, while theworst degraded are HCHs, endosulphan-sulphate, hep-tachlors epoxide, and 4,4′-dichlorobenzophenone.
