Appreciable Enhancement of Photocatalytic Performance for N-doped SrMoO_(4) via the Vapor-thermal Method

A series of nitrogen-doped SrMoO_(4) with different Sr/N mole ratio (R=0,0.05,0.10,0.15,0.20,0.40,and 0.60) were synthesized using urea as the N source via the vapor-thermal method.The photocatalytic degradation ability of all samples was evaluated using methylene blue (MB) as a target contaminant.The band gaps of N-doped samples are all higher than that of pristine ones,which is only 3.12 eV.BET specific surface area S_(BET) and pore volume are increased due to the N doping.And the greater increase of S_(BET),the faster the photodegradation speed of methylene blue on SrMoO_(4).More specifically,the degradation efficiency of MB is improved up to 87%in 100 min.

Enhanced visible-light photocatalytic oxidation capability of carbon-doped TiO_2 via coupling with fly ash

A carbon‐doped TiO2/fly ash support(C‐TiO2/FAS)composite photocatalyst was successfully synthesized through sol impregnation and subsequent carbonization.The carbon dopants were derived from the organic species generated during the synthesis of the C‐TiO2/FAS composite.A series of analytical techniques,such as scanning electron microscopy(SEM),attenuated total reflection‐Fourier transform infrared(ATR‐FTIR)spectroscopy,X‐ray photoelectron spectroscopy(XPS),and ultraviolet‐visible diffuse reflectance spectroscopy(UV‐Vis DRS),were used to characterize the properties of the prepared samples.The results indicated that C‐TiO2 was successfully coated on the FAS surface.Coupling between C‐TiO2 and FAS resulted in the formation of Si–O–C and Al–O–Ti bonds at their interface.The formation of Si–O–C and Al–O–Ti bonds gave rise to a positive shift of the valence band edge of C‐TiO2 and enhanced its oxidation capability of photogenerated holes as well as photodegradation efficiency of methyl orange.Moreover,the C‐TiO2/FAS photocatalyst exhibited favorable reusability and separability.This work may provide a new route for tuning the electronic band structure of TiO2.

A comparison study of alkali metal-doped g-C_3N_4 for visible-light photocatalytic hydrogen evolution

Photocatalytic hydrogen production based on semiconductor photocatalysts has been considered as one of the most promising strategies to resolve the global energy shortage.Graphitic carbon nitride(g‐C3N4)has been a star visible‐light photocatalyst in this field due to its various advantages.However,pristine g‐C3N4usually exhibits limited activity.Herein,to enhance the performance of g‐C3N4,alkali metal ion(Li+,Na+,or K+)‐doped g‐C3N4are prepared via facile high‐temperature treatment.The prepared samples are characterized and analyzed using the technique of XRD,ICP‐AES,SEM,UV‐vis DRS,BET,XPS,PL,TRPL,photoelectrochemical measurements,photocatalytic tests,etc.The resultant doped photocatalysts show enhanced visible‐light photocatalytic activities for hydrogen production,benefiting from the increased specific surface areas(which provide more active sites),decreased band gaps for extended visible‐light absorption,and improved electronic structures for efficient charge transfer.In particular,because of the optimal tuning of both microstructure and electronic structure,the Na‐doped g‐C3N4shows the most effective utilization of photogenerated electrons during the water reduction process.As a result,the highest photocatalytic performance is achieved over the Na‐doped g‐C3N4photocatalyst(18.7?mol/h),3.7times that of pristine g‐C3N4(5.0?mol/h).This work gives a systematic study for the understanding of doping effect of alkali metals in semiconductor photocatalysis.

Synthesis of M(M=Co^2+,Co^2+/Ni^2+)-doped FeS2 Nanospheres with Enhanced Visible-light-induced Photocatalytic Activity

Nano-spherical Co^（2＋）-doped FeS_2 was synthesized through a simple solvothermal method. The products were investigated using XRD, FE-SEM, BET, ICP, EDS, TEM, HRTEM, XPS, and UV-vis spectroscopy. The results indicated that Co^（2＋） ion could change the particle nucleation process and inhibited the particle growth of FeS_2. In addition, when the content of doped Co^（2＋） was 15%, the degradation efficiency of methylene blue（MB） achieved 60.72% after 210 min irradiation, which increased by 52.01% than that of the undoped FeS_2. Moreover, comparison experiments also demonstrated that the M（M=Co^2＋,Co^2＋/Ni^2＋）-doped FeS_2 photocatalytic activity efficiency sequence was Co^（2＋） 〉 Ni^（2＋）〉Co^（2＋）/Ni^（2＋）. This is ascribed to the fact that the Co^（2＋） doping could induce the absorption edge shifting into the visible-light region and increased the surface area of the samples. The effect mechanisms of M-doping on the band gap and the photocatalytic activity of FeS_2 were also discussed.

Preparation, Characterization, Photocatalytic Activity of S and Ag co-Doped Mesoporous Titania Photocatalysts

In order to improve the photocatalytic performance of mesoporous titania under visible light, a series of photocatalysts of S and Ag co-doped mesoporous titania have been successfully prepared by template method using thiourea, AgNO3 and tetrabutyl titanate as precursors and Pluronic P123 （EO20PO70EO20） as template. Scanning electron microscopy （SEM）, X-ray diffraction （XRD）, nitrogen adsorption-desorption measurements, and UV-visible spectroscopy （UV-Vis） were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The microcrystal of the photocatalysts consisted of anatase phase and was approximately present in the form of spherical particle. The photocatalytic performance was studied by photodegradation methyl orange （MO） in water under UV and visible light irradiation. The calcination temperature and the doping content influenced the photoactivity. In addition, the possibility of cyclic usage of co-doped mesoporous titania was also confirmed, the photocatalytic activity of mesoporous titania remained above 89% of that of the fresh sample after being used four times. It was shown that the co-doped mesoporous titania could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants. The synergistic effect of sulfur and silver co-doping played an important role in improving the photocatalytic activity.

Mg-doped SrTaO_(2)N as a visible-light-driven H_(2)-evolution photocatalyst for accelerated Z-scheme overall water splitting

Perovskite SrTaO_(2)N is one of the most promising narrow-bandgap photocatalysts for Z-scheme overall water splitting.However,the formation of defect states during thermal nitridation severely hinders the separation of charges,resulting in poor photocatalytic activity.In the present study,we successfully synthesize SrTaO_(2)N photocatalyst with low density of defect states,uniform morphology and particle size by flux-assisted one-pot nitridation combined with Mg doping.Some important parameters,such as the size of unit cell,the content of nitrogen,and microstructure,prove the successful doping of Mg.The defect-related carrier recombination has been significantly reduced by Mg doping,which effectively promotes the charge separation.Moreover,Mg doping induces a change of the band edge,which makes proton reduction have a stronger driving force.After modifying with the core/shell-structured Pt/Cr_(2)O_(3)cocatalyst,the H_(2)evolution activity of the optimized SrTaO_(2)N:Mg is 10 times that of the undoped SrTaO_(2)N,with an impressive apparent quantum yield of 1.51%at 420 nm.By coupling with Au-FeCoO_(x)modified BiVO_(4)as an O_(2)-evolution photocatalyst and[Fe(CN)_(6)]_(3)−/[Fe(CN)_(6)]_(4)−as the redox couple,a redox-based Z-scheme overall water splitting system is successfully constructed with an apparent quantum yield of 1.36%at 420 nm.This work provides an alternative way to prepare oxynitride semiconductors with reduced defects to promote the conversion of solar energy.

Preparation of Nano-TiO_2 Doped with Cerium and Its Photocatalytic Activity

Cerium-doped titanium dioxide nano-powders were prepared through the sol-gel method and the compound sampies were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and UV/Vis diffuse reflectance spectra （DRS）. The photocatalytic activity was evaluated by photocatalytic degradation of phenol in water. The results of XRD, TEM, and DRS show that pure TiO2 and Ce-doped TiO2 powder crystallines are a mixture of anatase and rutile ; the doping can retard the development of the grain size of TiO2 and decrease the diameter of TiO2 from more than 20 nm of pure TiO2 to about 10 nm; the doped TiO2 can improve the light absorption of TiO2 and suitable doping content tends to move the DRS spectrum of TiO2 towards visible light, but too much doping is not good for the light absorption ability. The results of the photocatalytic experiments show that doping with Ce content of 0.08% -0.4% can increase the photocatalytic activity of TiO2; however, doping with Ce content of 0.5% -2.5% can significantly decrease the photocatalytic activity of TiO2. The favorite doping content is 0.4% in the range of our experiments.

Characterization of metal doped-titanium dioxide and behaviors on photocatalytic oxidation of nitrogen oxides

A series of nanosized ion-doped TiO2 catalysts with different ion content （between 0.1 at.% and 1.0 at.%） have been prepared by wet impregnation method and investigated with respect to their behavior for UV photocatalytic oxidation of nitric oxide. The catalytic activity was correlated with structural, electronic and surface examinations of the catalysts using X-ray diffraction analysis （XRD）, ultraviolet-visible （UV-Vis） absorption spectroscopy, transmission electron microscopy （TEM）, energy disperse spectrometer （EDS） and high resolution-transmission electron microscopy （HR-TEM） techniques. An enhancement of the photocatalytic activity was observed for Zn2＋ doping catalyst ranged from 0.1 at.% to 1.0 at.% which was attributed to the lengthened lifetime of electrons and holes. The improvement in photocatalytic activity could be also observed with the low doping concentration of Cr^3＋ （0.1 at.%）. However, the doping of Fe^3＋, Mo^6＋, Mn^2＋ and the high doping concentration of Cr^3＋ had no contribution to photocatalytic activity of nitric oxide.

Synthesis and photocatalytic properties of lanthanum doped anatase TiO_2 coated Fe_3O_4 composites

A composite photocatalyst （La/TiO2/Fe3O4） with a lanthanum doped TiO2 （La/TiO2） shell and a magnetite core was prepared by coating photoactive La/TiO2 onto a magnetic Fe3O4 core. The morphological, structural, and optical properties of as-prepared samples were charac-terized by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and UV-vis absorption spectroscopy. The effect of lanthanum content on the photocatalytic properties was studied, and the result revealed that 0.15 mol% La/TiO2/Fe3O4 exhibited the highest photoactiv-ity. The photocatalytic properties of the prepared photocatalyst under UV and visible light were investigated in aqueous solution using methyl orange （MO） as a target pollutant. The results showed that the prepared photocatalyst was activated by visible light and used as an ef-fective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, La/TiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by a simple magnetic process.

Synthesis of iron(Ⅲ)-doped nanostructure TiO_2/SiO_2 and their photocatalytic activity

Iron（Ⅲ）-doped nanostructure TiO2-coated SiO2 （TiO2/SiO2） particles were prepared using the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized employing the sol-gel method with TiChas a precursor. The samples were characterized by Fourier transform infrared spectroscopy （FTIR）, SEM, EDS, XPS, and XRD. The experimental results show that TiO2 nanopowders on the surface of SiO2 particles are well distributed, the amount of TiO2 is increased with the adding of coating layers, the pure anatase-TiO2 coating layers are synthesized at 500℃, and the photocatalytic activity of Fe^3＋-doped TiO2/SiO2 is higher than that of undoped TiO2/SiO2.

Photocatalytic degradation of acid orange 7 in aqueous solution with La^(3+)-doped TiO_2 photocatalysts

Nanocrystalline La^3＋-doped TiO2 of 20-30 nm in size was prepared by a sol-gel technique. The photocatalytic activities of the samples were evaluated by the degradation of harmful acid orange 7（AO7） azo-dye in aqueous solution. The effects of La^3＋ ion implantation on the photocatalytic activity of TiO2 were also discussed. The results show that the La^3＋ content plays an essential role in affecting the photocatalytic activity of the La^3＋-doped TiO2 and the optimum content of La^3＋-doped is 1.0 wt.%. The photocatalytic activity of the samples with La^3＋-doped TiO2 is higher than that of pure TiO2 in the treatment of AO7 wastewater. The photodegradation effect of AO7 effluent is the best by means of La^3＋-doped TiO2 with 1.0% La^3＋.

Recent advances in non-metal doped titania for solar-driven photocatalytic/photoelectrochemical water-splitting

Photocatalytic (PC) / Photoelectrochemical (PEC) water splitting under solar light irradiation is considered as a prospective technique to support the sustainable and renewable H_(2) economy and to reach the ultime goal of carbon neutral. TiO_(2) based photocatalysts with high chemical stability and excellent photocatalytic properties have great potential for solar-to-H_(2) conversion. To conquer the challenges of the large band-gap and rapid recombination of photo generated electron-holepairs in TiO_(2), non-metal doping turns out to be economic, facile, and effective on boosting the visible light activity. The localized defect states such as oxygen vacancy and Ti^(3+) generated by non-metal doping are located in the band-gap of TiO_(2), which result in the reduction of band-gap, thus a red-shift of the absorption edge. The hetero doping atoms such as B^(3+), I^(7+), S^(4+)/S^(6+), P^(5+) can also act as electron donors or trap sites which facilitate the charge carrier separation and suppress the recombination of electron-hole pairs. In this comprehensive review, we present the most recent advances on non-metal doped TiO_(2) photocatalysts in terms of fundamental aspects, origin of visible light activity and the PC / PEC behaviours for water splitting. In particular, the characteristics of different non-metal elements (N, C, B, S, P, Halogens) as dopants are discussed in details focusing on the synthesis approaches, characterization as well as the efficiency of PC and PEC water splitting. The present review aims at guiding the readers who want quick access to helpful information about how to efficiently improve the performance of photocatalysts by simple doping strategies and could stimulate new intuitive into the new doping strategies.

Core-shell particles of C-doped CdS and graphene: A noble metal-free approach for efficient photocatalytic H_(2) generation

To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is reported.The doping effect and the application of graphene as cocatalyst for CdS is studied for photocatalytic H_(2) generation.The most active sample consists of CdS and graphene(CdS-0.15G)exhibits promising photocatalytic activity,producing 3.12 mmol g^-(1) h^-(1) of H_(2) under simulated solar light which is^4.6 times superior than pure CdS nanoparticles giving an apparent quantum efficiency(AQY)of 11.7%.The enhanced photocatalytic activity for H_(2) generation is associated to the narrowing of the bandgap,enhanced light absorption,fast interfacial charge transfer,and higher carrier density(N_(D))in C-doped CdS@G samples.This is achieved by C doping in CdS nanoparticles and the formation of a graphene shell over the C-doped CdS nanoparticles.After stability test,the spent catalysts sample was also characterized to investigate the nanostructure.

Hydrophilic bi-functional B-doped g-C_(3)N_(4) hierarchical architecture for excellent photocatalytic H_(2)O_(2) production and photoelectrochemical water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has attracted great interest in photocatalysis and photoelectrocatalysis.However,their poor hydrophilicity poses a great challenge for their applications in aqueous environment.Here,we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C_(3)N_(4)nanoplatelets.Such hierarchical B-doped g-C_(3)N_(4)material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium,leading to an excellent photocatalytic H_(2)O_(2)production rate of 4240.3μM g^(-1)h^(-1),2.84,2.64 and 2.13 times higher than that of the bulk g-C_(3)N_(4),g-C_(3)N_(4)nanoplatelets and bulk B doped g-C_(3)N_(4),respectively.Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 m A cm^(-2)at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting.This work makes a fundamental improvement towards large-scale exploitation of highly active,hydrophilic and stable metal-free g-C_(3)N_(4)photocatalysts for various practical applications.

Iron-Doped Titania Nanoparticles for the Photocatalytic Oxidative Degradation of Nitrite

Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO_2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0.5%. The increase in photoactivity is probably due to the higher adsorption and the inhibition of electron-hole recombination. The photocatalytic oxidation reaction of nitrite over the Fe-doped TiO_2 catalyst follows zero-order kinetics, which is different from that over pure TiO_2. The reaction rate decreases linearly with the increase of the pH of the solution.

Intrinsic photocatalytic water oxidation activity of Mn-doped ferroelectric BiFeO3

The development of stable and efficient visible light-absorbing oxide-based semiconductor photocatalysts is a desirable task for solar water splitting applications.Recently,we proposed that the low photocurrent density in film-based BiFeO_(3)(BFO)is due to charge recombination at the interface of the domain walls,which could be largely reduced in particulate photocatalyst systems.To demonstrate this hypothesis,in this work we synthesized particulate BFO and Mn-doped BiFeO_(3)(Mn-BFO)by the sol-gel method.Photocatalytic water oxidation tests showed that pure BFO had an intrinsic photocatalytic oxygen evolution reaction(OER)activity of 70μmol h^(-1) g^(-1),while BFO-2,with an optimum amount of Mn doping(0.05%),showed an OER activity of 255μmol h^(-1) g^(-1) under visible light(λ≥420 nm)irradiation.The bandgap of Mn-doped BFO could be reduced from 2.1 to 1.36 eV by varying the amount of Mn doping.Density functional theory(DFT)calculations suggested that surface Fe(rather than Mn)species serve as the active sites for water oxidation,because the overpotential for water oxidation on Fe species after Mn doping is 0.51 V,which is the lowest value measured for the different Fe and Mn species examined in this study.The improved photocatalytic water oxidation activity of Mn-BFO is ascribed to the synergistic effect of the bandgap narrowing,which increases the absorption of visible light,reduces the activation energy of water oxidation,and inhibits the recombination of photogenerated charges.This work demonstrates that Mn doping is an effective strategy to enhance the intrinsic photocatalytic water oxidation activity of particulate ferroelectric BFO photocatalysts.

Enhanced photocatalytic degradation properties of nitrogen-doped titania nanotube arrays

Nitrogen-doped TiO2 nanotubes array were synthesized to improve the photocatalytic efficiency by annealing the anodized titania nanotubes with ammonia at 500℃.Detailed structural analysis revealed that the nitrogen-doped titania nanotubes are of highly ordered structure,and exhibit a decreased phase transformation temperature compared with those that are not doped,as evidenced by the decrease in full width at half maximum(FWHM)of the(110)peak of rutile phase and the occurrence of the typical Raman peaks of rutile phase at 196,235,442,610 cm -1 .According to the photocatalytic degradation of methyl orange under visible light irradiation,the nitrogen-doped TiO2 nanotubes exhibit enhanced photocatalytic efficiency compared with their non-doped nanotubes,which might be a result of either the nitrogen doping induced band gap narrowing or the synergistic effect produced by both nitrogen and fluorine dopants.

Enhanced photocatalytic activity of (La, N) co-doped TiO_2 by TiCl_4 sol-gel autoigniting synthesis

（La, N） co-doped TiO2 photocatalysts were synthesized using TiC14 sol-gel autoignidng synthesis （SAS） starting from a complex compound system of TiCl4-La（NO3）3-citric acid-NH4NO3-NHyH2O, in which the （La, N） co-doped process was accompushed in the formation of TiO2 nanocrystals. The prepared samples were characterized by using X-ray diffraction （XRD）, X-ray photoemission spectroscopy （XPS） and UV-vis diffuse reflectance spectra. The results indicated that nitrogen and lanthanum were incorporated into the lattice and interstices of titania nanocrystals, which resulted in narrowing the band gap and promoting the separation of photoexcited hole-electron pairs, respectively, and showing expected red-shifts and enhanced photocatalytic activity under visible light. The mechanism on nitrogen doping and enhancement in photocatalyfic activity of （La, N） co-doped titania by SAS was discussed in detail.

Preparation and photocatalytic activity of Cu^(2+)-doped TiO_2/SiO_2

Cu^2＋-doped nanostructured TiO2-coated SiO2 （TiO2/SiO2） particles were prepared by the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized by the sol-gel method using TiOSO4 as a precursor. The experimental results showed that TiO2 nanopowders on the surface of SiO2 particles were well distributed and compact. The amount of TiO2 increased with the increase in coating layers. The shell structure appeared to be composed of anatase titania nanocrystals at 550℃. The 2-layer coated TiO2 particles on the surface showed a higher degradation rate compared with all the different-layer samples. The photocatalytic activity of Cu^2＋-doped TiO2/SiO2 was higher than that ofundoped TiO2/SiO2. The optimum dopant content was about 0.10wt%.

Synthesis of Pr-doped ZnO nanoparticles: Their structural,optical, and photocatalytic properties

Undoped and praseodymium-doped zinc oxide （Pr-doped ZnO） （with 2.0-mol%-6.0-mol% Pr） nanoparticles as sunlight-driven photocatalysts are synthesized by means of co-precipitation with nitrates followed by thermal annealing. The structure, morphology, and chemical bonding of the photocatalysts are studied by x-ray diffraction （XRD）, scanning electron microscopy （SEM） with energy dispersive x-ray emission spectroscopy （EDS）, x-ray photoelectron spectroscopy （XPS）, and Fourier transform infrared spectroscopy （FTIR）, respectively. The optical properties are studied by photolu- minescence （PL） and UV-vis diffuse reflectance spectroscopy （UV-vis DRS）. We find that Pr doping does not change the crystallinity of ZnO; but it reduces the bandgap slightly, and restrains the recombination of the photogenerated electron-hole pairs. The photocatalytic performance of the photocatalysts is investigated by the photodegradation reaction of 10-mg/L rhodamine B （RhB） solution under simulated sunlight irradiation, showing a degradation rate of 93.75% in ZnO doped with 6.0-mo1% Pr.