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Novel visible-light-driven dual-oxygen-doped porous g-C3N4 (OPCN) photocatalysts were synthesized by a facile thermal copolymerization of urea and ammonium oxalate. The introduced O atoms were preferable to synchronously substitute for two sp2-hybridized N atoms in the para-positions (i.e., N1′ and N4′ sites) of the melem unit by forming dual-O-doped g-C3N4. Together with porous structures, OPCN exhibited enlarged specific surface area, narrowed band gap and expanded visible light response. The photocatalytic activity of the optimal OPCN was approximately 9 times higher than that of pure g-C3N4 for bisphenol A (BPA) removal under visible light irradiation, and efficient removal rates for various chlorophenols, phenols and dyes were also observed. Combined with experiments and DFT calculations, this dual-O-doped structure resulted in effective charge transfer and separation of OPCN under visible light irradiation by forming e− and h+-related conjugated delocalized systems on the surface, which contributed to its interfacial contact with organic pollutants and adsorbed O2. As a result, the degradation of BPA was readily induced by photoinduced h+ and then thoroughly mineralized by O2 −. On the other hand, more O2 − radicals were generated, which could also oxidize BPA directly due to their strong oxidation power. The superior stability and reusability of OPCN catalysts were also revealed during photoreaction. This work provides a novel viewpoint to fabricate high-performance nonmetal photocatalysts for wastewater treatment.

Two atomically dispersed cobalt catalysts with different nitrogen coordination numbers (denoted as CoSA-Nx-C) were synthesized and firstly compared to activate peroxydisulfate (PDS) for bisphenol A (BPA) degradation. Theoretical calculations unveiled that lowering the Co N coordination number from four to three can apparently increase the electron density of the single Co atom in CoSA-N3-C to enhance PDS conversion. The low-coordinated CoSA-N3-C with Co N3 coordination structure displays a high specific activity of 0.067 L min 1 m 2, which is 1.31 times greater than that of CoSA-N4-C with normal Co N4 configuration (0.051 L min 1 m 2) in PDS activation. Electron paramagnetic resonance (EPR) measurements and quenching tests confirmed the primary role of sulfate radical (SO4●−) in BPA oxidation over CoSA-N3-C with PDS. Moreover, CoSA-N3-C delivers favorable durability for PDS activation and potential practicability for realistic wastewater remediation. These findings provide a novel and useful avenue to coordination number modulation of SACs for wider environmental applications.

A photocatalyst of layered structural BiOBr doped with sulfur (S-BiOBr) was synthesized using a facile hydrothermal method. X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory calculation revealed that S-BiOBr consisted of covalent [Bi2O2S]2+ layer and exchangeable bromide ions [Br2]2-. The specific layered structure of S-BiOBr exhibited excellent performance for the intercalation, adsorption and photocatalytic degradation of ciprofloxacin (CIP) by forming interlayer [Bi2O2S]2+--OOC-R complexes. Furthermore, the internal electric field enhanced by polarization effects in the [Bi2O2S]2+ layer was conducive to a lasting electron transfer in the dark condition after photoactivation. The electron of R• radical derived from oxidizing [Bi2O2S]-OOC-R persistently migrated to the S-BiOBr surface and was trapped by O2 to form O2•-, facilitating the degradation of CIP in the dark. Hence, the degradation of CIP could be realized by utilizing the R• radical triggered through transient photoinitiation with low optical energy consumption.

A novel self-sustaining monolithic photoelectrocatalytic/photovoltaic (SMPP) system is constructed with a FTO-glass-based WO3/BiVO4 photoanode, which was prepared by coating BiVO4on WO3 nanoplate array using simple wet chemical methods, a rear Si photovoltaic cell (PVC) and a counter Pt-black/Pt cathode. The optimum SMPP system shows an efficient and stable degradation of tetracycline hydrochloride with a rate constant 0.75 h−1, and yields an open circuit voltage 1.35 V, a short circuit current 2900 μA cm−2, a power density 1112 μW cm−2, which is nearly 14 times that of theultimate conventional photocatalytic fuel cell to date, and a hydrogen generation rate 52.6 μmol h−1 cm−2. This outstanding performance should be due to the efficient electron/hole separation and light exploitation, because, under stimulated sunlight illumination, the front WO3/BiVO4 photoanode absorbs short-wavelength photons and generates electron/hole pairs, in which the photogenerated holes can oxidize organics, while the rear Si PVC captures the transmitting longer-wavelength photons to generate photovoltage that drives photogenerated electrons to the cathode for reducing H+ to H2 and generating electricity in the external-circuit. The results also demonstrate that various refractory organics can be efficiently decomposed along with the production of electricity and hydrogen by the SMPP system. This work provides a more efficient way to dispose organics and simultaneously produce clean energy than conventional technologies and serves well as a promising technology for wastewater recycling.

A layered BiO(OH)xI1-x solid solution was grown in situ on the surface of AgI particles by a one-pot co-crystallization method. Based on the results of XPS, EPR, XRD and other techniques, it was verified that a p-n heterojunction was formed through Ag-I-Bi cross-linking bonds in the interface of BiO(OH)xI1-x and AgI due to the common species of I− ions. The resulting BiO(OH)xI1-x-AgI exhibited high efficiency and stability for photodegradation of phenolic compounds with visible light irradiation. No significant AgI decomposition or release of Ag+ or Bi3+ was observed in the photoreaction, and the photoactivity of AgI was enhanced almost 9-fold. These enhanced photocatalytic properties were attributed to the strong interfacial interaction between BiO(OH)xI1-x and AgI by the Ag-I-Bi bond junction. Due to the chemical-bond junction, the photogenerated electrons in the CB of AgI quickly transferred to the CB of BiO(OH)xI1-x to produce O2 －, while the holes in the VB of BiO(OH)xI1-x migrated to the VB of AgI to oxidize pollutants in water. The accelerated interfacial charge transfers were responsible for the high photostability and photoactivity of BiO(OH)xI1-x-AgI.

Cu-doped AlPO4 molecular sieve was prepared by a hydrothermal method and characterized by field emission scanning electron microscope, X-ray diffraction, extended X-ray absorption fine structure, X-ray photoelectron spectroscopy and nitrogen adsorption/desorption isotherms. The Cu(0.05)-AlPO4 with Cu/Al molar ratio of 0.05 was highly effective and stable for the degradation of bisphenol A (BPA) in the presence of H2O2 at room temperature and neutral pH conditions. The characterization results confirmed that Cu(II)/Cu(I) was co-incorporated into AlPO4 molecular sieve by chemical bonding of Cu O T (T for Al or P) in Cu(0.05)-AlPO4, increasing the BET surface area of AlPO4 for more active sites. Excessive copper species existed in the form of Cu(II) and located in the extraframework sites, blocking the porous structure to decrease the specific surface area of AlPO4. The studies of electron spin resonance, in situ Raman spectra and other experiments verified that H2O2 was predominately converted into OH and HO2 /O2 − in Cu(0.05)-AlPO4 suspension. Specially, the presence of BPA in Cu(0.05)-AlPO4 suspension promoted the convertion of H2O2 into OH. A mechanism of heterogeneous Fenton catalysis was proposed on the basis of the cycle between Cu(I) and phenoxo-Cu(II) complexes during the interaction of Cu(0.05)-AlPO4, BPA and H2O2.

A close-connected p-AgI/n-Bi2O2CO3 heterojunction was synthesized by a one-step co-crystallization method. The visible-light-driven photoactivity of AgI was exceptionally enhanced by nearly 5 times through in-situ close contact with Bi2O2CO3. After seven cycling measurements, the photodegradation rate of 2-chlorophenol could be maintained at 88% and no Ag+ and Bi3+ could be detected in the reaction solution, indicating high photostability of the heterojunction photocatalyst. On the basis of the characterization of morphology, X-ray diffraction, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy, AgI nanoparticles were selectively anchored on active {001} facets of layered Bi2O2CO3 sheets, and a strong interfacial interaction between p-AgI and n-Bi2O2CO3 was observed, which enhanced effective separation and transfer of the photo-generated electron-hole pair from AgI, resulting in the high photoactivity and photostability of AgI for the degradation and mineralization of 2-chlorophenol under visible light. By the studies of electron spin resonance and other experiments, the charge transfer process at the interface of p-AgI/n-Bi2O2CO3 was verified that the photoexcited electrons of the conduction band of AgI transferred to the conduction band of Bi2O2CO3 to react with surface adsorbed oxygen into O2 –, while the photoexcited holes of the valence band of AgI could oxidize organic pollutants in water.

Titanium-doped mesoporous γ-Al2O3 (γ-Ti-Al2O3) was prepared by an evaporation-induced self-assembly method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption, scanning electron microscope, and FTIR spectra of chemisorbed pyridine. γ-Ti-Al2O3 revealed excellent catalytic ozonation activity and stability for mineralization of six drugs in aqueous solution, including ibuprofen, sulfamethoxazole, phenytoin, diphenhydramine, diclofenac sodium and acyclovir. The characterization studies showed that titanium was incorporated into the framework of γ-Al2O3 by Al O Ti linkage, locating at tetrahedrally coordinated sites, which increased the Lewis acid sites of γ-Al2O3, especially the medium acid sites. The surface atomic oxygen ( Al3−*O) and peroxide species ( Ti4+−*O2) were commonly generated rather than hydroxyl radical from catalytic decomposition of ozone in γ-Ti-Al2O3 suspension on the basis of the electron paramagnetic resonance (EPR) and in situ Raman measurements. Furthermore, it was verified that the high mineralization of the tested pharmaceuticals came from the surface oxidization of organic acid intermediates by the common role of the surface atomic oxygen and peroxide species.

Orbital interaction involving metal cation−π is an important form for electron transfer regulation. To accelerate the interfacial electron transfer of peroxymonosulfate (PMS) activation for water treatment, we report a new strategy through bonding atomically dispersed cobalt with nanospheric C-based graphene-like structures (SACo-NGs) to form metal cation−π structure, driving rapid and directional transfer of the electrons of pollutants to PMS on the catalyst surface. The catalyst SACo-NGs is synthesized by an enhanced hydrothermal-sintering method and the formation of metal cation−π structure is demonstrated by X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR) and Raman spectroscopy. It is found that Co−π structures (Co2+-N-Cπ) play a key role for the efficient activation of PMS, which results in pollutants being greatly removed in a few minutes. During the reaction, pollutants can donate electrons for the system through π−π interaction accompanying by the direct oxidative degradation of pollutants. The obtained electrons are quickly transferred to the atomically dispersed cobalt sites through the formed cation−π structure, which promotes the activation of PMS. This is a successful practice in the field of PMS activation using cation−π structure to accelerate electron transfer and achieve rapid degradation of pollutants.

Solid solution of BiOBr and BHO (BiO(OH) 0.06 Br 0.94 ) with abundant oxygen vacancies was supported on Ag/AgBr using precipitation and deposition–precipitation methods. The photocatalyst showed high and stable photocatalytic activity for the degradation of chlorophenols and azodyes in water under visible to NIR light irradiation without any release of Ag + , which came from visible-excited AgBr and the SPR of Ag NPs in the visible and NIR region. The different interfacial charge-transfer processes were verified on the basis of cyclic voltammetry analyses and all experimental information. The conduction band (CB) electrons of photoexcited AgBr reacted with the adsorbed oxygen forming O 2 •− , while the valence band (VB) holes of AgBr were transported the VB of BiO(OH) 0.06 Br 0.94 to oxidize organic pollutants or H 2 O to • OH. The plasmon-induced electrons from Ag NPs transferred to the CB of AgBr reacting with the adsorbed oxygen to O 2 •− , while the electrons trapped on the oxygen vacancies of BiO(OH) 0.06 Br 0.94 transferred to Ag NPs recombining with the plasmon-induced holes, inhibiting the release of Ag + , and the resulted VB holes of BiO(OH) 0.06 Br 0.94 oxidized organic compound. These interfacial charge transfers evidenced the high photoactivity and photostability of BiO(OH) 0.06 Br 0.94 /Ag/AgBr.

An innovative benzene-ring grafted g-C3N4 nanotubes (AHCN) were prepared by thermal-polymerization of the self-assembled supramolecular composed of melamine (MA) and phloroglucinol (PG). MA is molecular self-assembly with PG to form nanorod-like supramolecular intermediate (N-MA-PG) in the hydrothermal process. Consequently, the PG in N-MA-PG acts as in-situ benzene-ring-doping source and shape-preserving-agent in the thermal polymerization conversion of N-MA-PG to AHCN. Benefited from the synergistic effect of nanotubular structure and benzene-ring grafting, AHCN shows stronger visible-light absorption, higher surface area, enhanced charge’s separation efficiency, leading to an excellent photocatalytic H2 evolution rate of 2780 μmol h−1 g-1 under visible light irradiation, which is obviously superior to that of pristine g-C3N4 (187 μmol h−1 g−1), g-C3N4 nanotubes (512 μmol h−1 g−1) and benzene-ring grafted g-C3N4 (666 μmol h−1 g−1). The apparent quantum efficiency of AHCN is achieved at 6.21 % at λ =420 nm. This work proposes a route to develop high-photocatalytic activity g-C3N4 through nanostructure controlling and molecular doping simultaneously.

The adsorptive behavior and photoreduction processes of CrO42− were investigated in 110-BiOBr and 001-BiOBr suspensions without/with visible-light irradiation. On the basis of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) measurements, CrO42- ions were adsorbed on the surface of 001-BiOBr in the form of = Bi-O-Cr-O3- complexes, and their photoreduction depended on the pH of the solution. By contrast, CrO42- were predominantly intercalated into the bulk of 110-BiOBr, forming [OBi]+-(O-CrO2-O)2--[BiO]+ complexes. It was found that 110-BiOBr showed higher efficiency for photoreduction of CrO42- at pH 2 and 7. Density functional theory (DFT) calculation further revealed that both the acceptor Cr 3d and donor O 2p of CrO42- impurity levels were introduced into 110-BiOBr bulk, enlarging the visible absorption range of BiOBr. Therefore, the photoreduction of Cr(VI) occurred by direct photo-generated electron transfer from the improved valence band of 110-BiOBr to the Cr 3d orbitals for reduction of Cr(VI) to Cr(III) without the involvement of H+.

Peroxymonosulfate (PMS) activation in heterogeneous processes for pollutant degradation is a promising water purification technology. However, the existed rate limiting step greatly restrains its performance and increases the consumption of PMS and energy. Herein, we offer a new strategy to solve this problem. In this work, surface oxygen vacancy (VO)-rich ZnFe0.8Co0.4O2.4 nanoparticles were prepared and characterized, which exhibited high activity and stability for refractory pollutant degradation with PMS activation. It was found that PMS ([O3S OI OII H]−) could be adsorbed and trapped by the surface oxygen vacancies in the form of OI-Vo or OII-Vo during the reaction. Different electron transfer pathways from Vo to different O sites of PMS was realized in the solid-liquid interface based on the generation of OH, SO4 − or H2 from PMS reduction. Pollutants were predominantly adsorbed at metal Co sites in which their electrons were captured by metal species and then transferred to the surface oxygen vacancies, achieving efficient recycling of electrons in the aqueous suspensions. This system achieves a dual-pathway degradation of pollutants and electron transfer from pollutants to PMS to produce free radicals and H2, essentially changing the traditional concepts of pollutant removal and providing a sustainable strategy for pollutant utilization during water purification.

A two-dimensional graphene/g-C3N4 in-plane hybrid heterostructure (DCN-Cg), which achieved ∼32.0-fold enhanced visible-light photocatalytic performance for pollutant degradation compared to bulk g-C3N4, was prepared by a self-conversion process. The characterizations indicated that graphene was stitched onto the edge of carbon nitride, not only extending the photoabsorption to energies below intrinsic bandgap, but also strengthening the interaction between pollutants and catalyst surface by π-π and hydrogen bonds. The stronger interaction promoted the polarization of charge distribution of DCN-Cg to further enhance the separation and transfer of photogenerated e-/h+, providing an efficient pathway for electron transfer from pollutants to DCN-Cg. Both interfacial electron transfer processes were verified that the photoexcited electrons are rapidly transferred from carbon nitride part to graphene by π-conjugated bond-stitched structure and trapped by O2 to generate O2- for degradation of pollutants. Meanwhile, adsorbed pollutants is decomposed by transferring electrons to the positive holes on the valence band of DCN-Cg.

Porous β-Bi2O3 with highly exposed {220} facets was fabricated for the first time and the formation of surface multiple Bi-O vacancy associates was confirmed by the photoluminescence, positron annihilation spectra, and theoretical calculations. Compared with traditional nonporous β-Bi2O3-{201}, the photocatalytic rate of porous β-Bi2O3-{220} was more than twice faster and the photoconversion efficiency increased by 20 times. And various refractory organic pollutants can be effectively degraded and mineralized under visible light. Multiple Bi-O vacancy associates were demonstrated to change electronic structure and enhance the polarization of the related atoms and orbitals. The photogenerated charge separation and transfer was thus improved to produce more surface active species. Simultaneously, the electron transfer from pollutants to the catalyst was found to be accelerated, finally leading to the outstanding photocatalytic performances of porous β-Bi2O3-{220}. These findings provide useful insights into the development of visible-light-driven photocatalysts for water purification.

A novel Ce-doped manganese oxide octahedral molecular sieve (Ce-OMS-2) was prepared by a reflux method and characterized by field emission scanning electron microscope, high resolution transmission electron microscopy, Fourier-transform infrared spectra, nitrogen adsorption/desorption isotherms, X-ray diffraction and X-ray photoelectron spectroscopy. The Ce(0.48)-OMS-2 with Ce/Mn molar ratio of 0.48 was highly effective and stable for the degradation of ciprofloxacin in water. The characterized results indicated that Ce mainly entered the tunnel structure of OMS-2, significantly increasing the BET surface area from 72 m 2 /g for OMS-2 to 304 m 2 /g for Ce(0.48)-OMS-2. Moreover, the surface oxygen defects and surface labile oxygen significantly increased after the introduction of Ce into OMS-2, being determined by the O1s spectra and O 2 -TPD analysis. The ESR and activity tests under different conditions suggested that the reduced manganese Mn(II) could interact with surface labile oxygen to form O 2 − and Mn(IV), resulting in the high activity of Ce(0.48)-OMS-2 to degrade the piperazine ring and the quinolone moiety of CIP into small molecular products. Simultaneously, the release of Mn(II) was inhibited by the electron transfer process on the micro-interface of Ce(0.48)-OMS-2.

Ag–Ag2O was prepared by precipitation and thermal decomposition and characterized by X-ray diffraction and high-resolution transmission electron microscopy. A well-matched interfacial contact was formed between the Ag and Ag2O nanoparticles (NPs) by drying Ag2O at 70–100 °C. The nanocomposites exhibited a higher photoactivity and stability for the degradation and mineralization of toxic persistent organic pollutants compared to Ag2O, which was demonstrated using 2-chlorophenol, 2,4-dichlorophenol and trichlorophenol under visible or near-infrared light irradiation and simulated solar irradiation. Based on electron storage and transient photocurrent, laser flash photolysis, and electron spin resonance analyses under a variety of experimental conditions, two sequential electron transfer processes were verified from photoexcited Ag2O to Ag NPs to a thionine molecule or surface adsorbed oxygen as well as from water to the Ag2O, resulting in O2 − and OH. The maximum electron storage, the longest lifetime (757 μs) of photogenerated electrons and the strongest steady state photocurrent were observed for Ag–Ag2O-70 °C, which resulted in the highest solar photoactivity. However, electron-hole recombination was dominant in the Ag–Ag2O dried in other temperature ranges, leading to a much lower photoactivity. The results indicated that the interfacial contact with the metal/semiconductor played a key role in charge separation and migration, which improved their photocatalytic efficiency. These results will allow for the application of narrow bandgap semiconductors that can harvest the full spectrum of sunlight to be employed in photocatalysis and photovoltaic fuel cells.

A plasmonic photocatalyst Cu2O-Ag-AgBr supported on mesoporous alumina (Cu2O-Ag-AgBr/Al2O3) was prepared by deposition-precipitation methods. The samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that Cu2O-Ag-AgBr nanojunctions were formed by the contact of Cu2O, AgBr and Ag with each other. The catalyst showed high photocatalytic activity and stability for the degradation of toxic persistent organic pollutants under visible light irradiation. The release of metal ions from the catalyst was significantly inhibited during the photodegradation of pollutants. Four interfacial electron transfer process were verified in the photoreaction system of Cu2O-Ag-AgBr/Al2O3 on the basis of electron spin resonance and cyclic voltammetry analyses under a variety of experimental conditions. The results indicated that the coupling of Cu2O with Ag NPs and AgBr not only accelerated interfacial electron transfer processes, leading to the fast photoreduction of the dissolved Ag+ and the photostability of Cu2O. These findings could be useful for the practical application of plasmonic visible light photocatalyst and photovoltaic fuel cells. (C) 2014 Elsevier B.V. All rights reserved.

BrO3- formation was investigated over beta-FeOOH/Al2O3 during the catalytic ozonation of Br--containing water. The effect of several representative compounds in aqueous environment such as 2,4-dichlorophenoxyacetic acid (2,4-D), phenazone (PZ), diphenhydramine (DP), amitrole (AMT) and Br--containing raw drinking water was examined on the formation of BrO3-. No significant BrO3- formation and higher removal of total organic carbon (TOC) were observed during the catalytic ozonation of the tested samples except AMT. Moreover, it was found that the adsorbed BrO3- was reduced to Br-, which was greatly enhanced by the degradation of organics according to the order AMT l DP l PZ l 2,4-D. The surface Fe(II) of beta-FeOOH/Al2O3 was responsible for the reduction of BrO3- on the basis of in situ diffuse reflection UV-vis spectra and the determination of surface Fe(II) under different conditions. It was generated from the reaction of surface Fe(III) with HO2 center dot-/O-2(center dot-) during the catalytic ozonation of different pollutants. Furthermore, FTIR and GC-MS analysis verified that the complexation of surface Fe(III) with the oxygen-containing functional groups ( OH, COOH) of pollutants or their intermediates enhanced the reaction of Fe(III) with HO2 center dot-/O-2(center dot-), resulting in more surface Fe(II) to cause higher BrO3- reduction rate. The catalyst still showed effectiveness for the inhibition of BrO3- formation and TOC removal for a Br--containing raw drinking water under the realistic conditions. These findings could be applied to the minimization of BrO3- formation in catalytic ozonation of Br--containing drinking water. (C) 2013 Elsevier B.V. All rights reserved.

Photogenerated electron-hole recombination has been a bottleneck problem for photocatalytic reactions for a long time. Herein, we propose an efficient solution strategy through capturing electrons and holes with environmental factors. In this study, nanoscale iron molybdate (Fe2(MoO4)3) was successfully synthesized, characterized and used in a heterogeneous photo-combined persulfate (PS) activation (HPPA) process for micropollutant removal. The reaction rate in this system was ˜98 and ˜59 times higher for Fenton-like and photocatalytic oxidation alone, respectively, which was attributed to strong synergistic effects of HPPA process. During the HPPA reaction, PS could quickly capture the photogenerated electrons to produce sulfate radicals (SO4 −), which was further converted to hydroxyl radicals (•OH) in water. Induced by PS, the electron-rich pollutants could actively capture the holes and be oxidized and degraded. This synergistic process not only inhibited the electron-hole recombination but also enabled rapid dual-pathway degradation of pollutants through free radical attack and hole oxidation.

Graphitic carbon nitride (g-C3N4), as metal-free and visible-light-driven photocatalyst, has been a promising alternative to replace the traditional inorganic photocatalyst. Herein, a dual oxygen group (C-O-C and C = O) doped carbon nitride (ACN*) was prepared by a two-step thermal treatment process. The photocatalyst showed high and stable photocatalytic activity for the degradation and mineralization of refractory organic pollutants under visible light irradiation, as demonstrated with bisphenol A, phenol, 2-chlorphenol and diphenhydramine. By electron paramagnetic resonance spectroscopy and density functional theory calculations, higher valence-electron densities were formed around the O atoms of C-O-C and C = O groups than around C and N atoms, constructing an internal electric field in ACN*, which was enhanced by light irradiation and the adsorption of pollutants by hydrogen bond and π-π bond interactions. Correspondingly, transfer processes of photogenerated carriers were proposed based on all experimental information obtained for pollutant photodegradation, including transfer of photoexcited electrons to the region around O atoms in the two types of oxygen groups, reaction with O2 to form •O- 2, and donation of electrons from adsorbed pollutants to electron-poor tri-s-triazine motifs in ACN*. The synergetic oxidation by the two processes contributed to higher photodegradation of pollutants. This correlation between the transfer of photogenerated carries and pollutant degradation shed a new light on the construction of internal electric field in carbon nitride photocatalysis.

Bi vacancies and Bi0 containing Bi2MoO6 (Bi0-Bi2-δMoO6) was synthesized by a facile chemical reduction method. The visible-light-driven photoactivity of Bi2MoO6 was enhanced by nearly 7 times due to the synergy of Bi vacancies and Bi0. Based on the characterization of XRD, HRTEM, XRF, XPS, Raman, FTIR and PL, Bi vacancies and Bi0 coexisted in the crystal lattice of Bi2MoO6, and a strong interaction between Bi0 and Bi2-δMoO6 was observed. Bi vacancies were proved to enlarge the band gap to promote the separation of photogenerated electron-hole pairs, and Bi0 can act as an electron trap to accelerate the charge transfer by its strong interaction with Bi2-δMoO6, resulting in the high photoactivity of Bi0-Bi2-δMoO6 for the degradation of various organic pollutants under visible light. By the studies of ESR and other experiments, the charge transfer process was clarified that the fast separated electrons from Bi2-δMoO6 by Bi vacancies were transferred to Bi0 and further reacted to produce O2•−, and thus the photoexcited holes were accelerated to transfer to the surface of Bi2-δMoO6 to oxidize water into more •OH and directly degrade organic pollutants in water.

a b s t r a c t Cu-doped LaTiO3 perovskite was prepared with a sol–gel method and characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The introduction of Cu induced the formation of LaTiO3 perovskite in which titanium existed as Ti 3+ , resulting in the coexistence of Ti 3+/4+ and Cu +/2+ in the perovskite structure. LaTi0.4Cu0.6O3 showed highly Fenton activity and stability for the degradation of RhB with H2O2 in the initial pH range of 4–9. Moreover, the catalyst buffered the solution with the tested initial pH to around 7 during the adsorption process. The studies of electron spin resonance, the effect of radical scav

Magnetic cobalt-doped Fe3O4 (FeCo) was prepared using a co-precipitation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The catalyst showed high, stable catalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with the herbicides 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenol, and 2,4,6-trichlorophenol and pharmaceutical phenazone in aqueous solution with ozone. FeCo was very effective at the mineralization of refractory oxalic acid produced in the degradation of organic compounds. The ozone was adsorbed on the surface of FeCo competing with water molecules in the aqueous phase, and converted into hydroxyl radical, meanwhile the catalyst surface underwent oxidation and reduction as demonstrated by in situ ATR-FTIR, CV and other experimental data obtained. Furthermore, the characterization studies indicated that the introduction of Co increased the rate of FeCo oxidation and reduction during the decomposition of ozone, enhancing the activity and stability of Fe3O4. (c) 2012 Elsevier B.V. All rights reserved.

The search for solid state materials with high catalytic activities and with no leaching into the reaction medium is one of the key steps toward reducing the cost of producing biodiesel. We report a high biodiesel yield (>95%) in less than 5 min under mild reaction conditions ( 2 O 2 CO 3 heterogeneous catalyst, showing no catalyst leaching into the reaction medium. The ZnO/La 2 O 2 CO 3 catalyst is prepared by a co-precipitation method and characterized by X-ray diffraction (XRD), thermogravimetric analyses (TGA), transmission electron microscopy (SEM), and transmission electron microscopy (TEM). The fatty acid methyl ester (FAME) yields as function of different amounts of catalyst was also investigated. Less than 1.0 wt.% catalyst can be used in the reaction to get higher than a 95% FAME yield under mild reaction conditions. The catalytic performance is maintained after storing the catalyst in Ar for a month and no catalyst leaching into the products was found based on XRF analysis. The catalyst has a higher reaction rate than the homogeneous KOH catalyst with the assistance of microwave irradiation. All of these results promote the industrial application of the synthesized ZnO/La 2 O 2 CO 3 as an ideal catalyst for fast biodiesel production, avoiding many of the issues found in both commercial and independently published catalysts.

Magnetic Co- and Co, Mn-doped gamma-Fe2O3 (FC and FCM) were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in situ attenuated total reflection FTIR (ATR-FTIR) spectroscopy and cyclic voltammetry (CV) analyses. FCM was found to be highly effective for the mineralization of 2,4-dichlorophenoxyacetic acid and its derivatives 2,4-diclorophenol, 2,4,6-trichlorophenol in aqueous solution with ozone. The characterization studies showed that Co and Mn incorporated in gamma-Fe2O3 existed as multivalence oxidation states, and there were more Lewis acid sites on the surface of FCM. The interaction of ozone with chemisorbed H2O and surface hydroxyl groups generated from dissociative adsorption of H2O on Lewis acid sites initiated the production of reactive oxygen species. Moreover, a redox process was observed in the catalytic decomposition of O-3 at the water-catalyst interface by CV analysis. The results indicated that the introduction of Mn not only increased the surface Lewis acid sites of FCM to cause more surface hydroxyl groups and chemisorbed water, but also enhanced the interfacial electron transfer, resulting in higher activity. (C) 2010 Elsevier B.V. All rights reserved.

Binary copper manganese oxides were prepared by a novel redox method and their catalytic activity for CO oxidation at ambient temperature evaluated. The catalytic activity was found to be high, and compared favorably with a commercial Hopcalite catalyst. The most active catalyst was able to completely oxidize CO at ambient temperature. Catalytic activity decay, most likely due to carbon dioxide retention was observed. The catalysts were deactivated by moisture but expelling water at moderate temperatures easily restored their catalytic activity. The catalysts were characterized by means of BET, FE-SEM, TEM, EDAX, XPS, TPD and X-ray powder diffraction. The optimum copper loading was determined to be ∼9% of the manganese content.

The surface acidity and reactive activity of beta-FeOOH. mesoporous alumina (MA), beta-FeOOH/MA were investigated in catalytic ozonation of pharmaceutically active compounds (PhACs) aqueous solution. beta-FeOOH/MA showed high efficiency for the degradation and mineralization of ibuprofen and ciprofloxacin. Its surface Lewis acid sites on beta-FeOOH/MA were more greatly enhanced compared with those on MA and beta-FeOOH. In situ attenuated total reflection FTIR (ATR-FTIR) spectroscopy was used to investigate the interaction of D2O and O-3 with the catalysts in aqueous phase under various conditions. The dissociative chemisorptions of D2O occurred at the surface Lewis acid sites of the catalyst. Furthermore, O-3 interacted with the surface hydrogen-bonded -O-D and D2O to initiate reactive oxygen species (ROS). The stronger Lewis acid sites of beta-FeOOH/MA caused the more chemisorbed water enhancing the interaction with ozone, resulting in higher catalytic reactivity. The observations verified that the Lewis acid sites were reactive centers for the catalytic ozonation of PhACs in water. (C) 2010 Elsevier B.V. All rights reserved.

CuOx-doped α-FeOOH (CuOx–FeOOH) nanorods were synthesized by controlling the reaction between ferrous sulfate, cupric sulfate and sodium borohydride at ambient atmosphere. The resulting materials were characterized by transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. CuOx–FeOOH was mainly composed of α-FeOOH and CuOx (CuO and Cu2O). The catalyst was found to be highly effective for the degradation of endocrine disruptors, including dimethyl phthalate, 2,4-dichlorophenoxyacetic acid, and 2,4-dichlorophenol in the presence of H2O2 and UVA at neutral pH. By the total organic carbon and GC–MS analysis, the degradation process of DMP was shown to proceed with the cleavage of C–O bond in ester linkages and the phenyl ring opening into organic acids and CO2. The studies of OH formation and cyclic voltammetry revealed that the H2O2 was decomposed into OH or O2 by the promotion of metal oxide. The obtained results showed that the synergistic effect between CuOx and α-FeOOH markedly enhanced the H2O2 decomposition into OH in CuOx–FeOOH suspension, causing the higher catalytic reactivity. A possible reaction mechanism was proposed.

Fe-200 was synthesized through the calcination of iron powder at 200 degrees C for 30 min in air. On the basis of characterization by X-ray diffraction and X-ray photoelectron spectroscopy, Fe-200 had a core-shell structure, in which the surface layer was mainly composed of Fe2O3, with some FeOOH and FeO. and the core retained metallic iron. The kinetics and mechanism of the interfacial electron transfer on Fe-200 were investigated in detail for the photoassisted degradation of organic pollutants with H2O2. Under deoxygenated conditions in the dark, the generation of hydroxyl radicals in aqueous Fe-200 dispersion verified that galvanic cells existed at the interface of Fe-0/iron oxide, indicating the electron transfer from Fe-0 to Fe3+. Furthermore, the effects of hydrogen peroxide and different organic pollutants on the interfacial electron transfer were examined by the change rate of the Fe3+ concentration in the solution. The results indicated that hydrogen peroxide provided a driving force in the electron transfer from Fe2+ to Fe3+. while the degradation of organic pollutants increased the electron transfer at the interface of Fe-0/iron oxide due to their reaction with center dot OH. (C) 2008 Elsevier B.V. All rights reserved.

The photocatalytic inactivation of pathogenic bacteria in water was investigated systematically with AgBr/TiO2 under visible light (lambda > 420 nm) irradiation. The catalyst was found to be highly effective for the killing of Escherichia coli, a Gram-negative bacterium, and Staphylococcus aureus, a Gram-positive bacterium. The decomposition of the cell wall and cell membrane was directly observed by TEM and further confirmed by K+ leakage from the inactivated bacteria. A possible cell damage mechanism by visible light-driven AgBr/TiO2 is proposed. In addition, the effects of pH, inorganic ions on bacterial photocatalytic inactivation were investigated. The electrostatic force interaction of the bacteria-catalyst is crucial for the efficiency of disinfection. Moreover, AgBr/TiO2 Supported on porous nickel showed much higher bactericidal activity than fixed P25 TiO2 under visible or near UV light irradiation. (c) 2007 Elsevier B.V. All rights reserved.

Hydroxyapatite (Ca-10(PO4)(6)(OH)(2): HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag+, Cu2+ or Zn2+) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO2 film. The studies of ESR revealed that not only O-2(center dot-) was formed on HAPTiM, HAPTi, HAP and P25-TiO2 films under weak UVA irradiation, but also at ambient temperature without light O-2(center dot-) was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu-0/Cu2+ and Ag-0/Ag+ in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O-2(center dot-) generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O-2(center dot-) and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K+) leakage from the killed bacteria. (c) 2007 Elsevier B.V. All rights reserved.

A monoclinic structure SrBi2O4 was prepared by coprecipitation method and characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and diffuse reflection UV–vis spectra (DRS). Photocatalytic activity of the catalysts was evaluated through the degradation of acetaldehyde and Escherichia coli (E. coli) under visible light irradiation (λ > 420 nm). The results indicated that monoclinic structure SrBi2O4 shows visible light activity and its photocatalytic activity was greatly enhanced when further loaded with NiO by the impregnation method. This is attributed to NiO promoting the electron–hole separation and interfacial charge transfer. The FT-IR spectra of the used NiO/SrBi2O4 indicated that some intermediates such as acetic acid, H2O, CO2 were formed for the degradation of acetaldehyde. The determination of intracellular K+ leakage with the inactivation of E. coli verified that the outer membrane of the cell is destroyed, causing the cell to die under visible light excitation of NiO/SrBi2O4. ESR studies revealed that OH, O2 − were involved as the active species in the photocatalytic reaction. A possible visible light photocatalytic mechanism was proposed.

Effects of acidity and inorganic ions that are common in industrial effluent on the photocatalytic degradation of azo dyes, Procion Red MX-5B (MX-5B) and Cationic Blue X-GRL (CBX), have been investigated in UV illuminated TiO2 dispersions. There are significant differences between adsorption and photodegradation of MX-5B and those of CBX to the change of solution pH. The results indicated that CBX photodegradation was favored at the surface of TiO2, while that of MX-5B occurred in the aqueous phase. At pH 2.4, SO42-, H2PO4-, ClO4- and F- in general increased the decolorization rates of MX-5B and CBX by enhancing the adsorption of the selected dyes on the surface of TiO2. At pH 10.8, most of the selected anions inhibited the photocatalytic oxidation (PCO) to decolorize and degrade CBX and MX-5B. These results demonstrated that inorganic anions affect the photodegradation of dyes by their adsorption onto the surface of TiO2 and trapping positive hole (h(+)) and (OH)-O-.. Inorganic cationic ions, such as Cu2+ and Ni2+ had strong inhibition on the PCO decolorization of MX-5B at pH 10.8. On the contrary, no significant effect was observed at the same concentration of metal cations at pH 2.4. (C) 2003 Elsevier Science B.V. All rights reserved.

Photocatalytic degradation of cationic blue X-GRL (CBX), a strongly adsorbing substrate on TiO2/SiO2, has been investigated by diffuse reflection UV–VIS spectra (UV–visible/DRS) and FT-IR methods. The heterogeneous photocatalysis processes include: adsorption of dye, surface reaction and desorption of final products. The adsorption of CBX onto the surface of TiO2/SiO2 was characterized, and the effect of initial pH of solution on the adsorption was determined. The results demonstrated that CBX was strongly adsorbed at the TiO− site of the catalyst by a penta-heterocyclic-N group. The adsorbed CBX was monitored directly by the UV–VIS/DRS technique during the photodegradation. The results confirmed that the surface photodegradation reaction of CBX was predominantly procedure with the mechanism of direct charge transfer from the semiconductor to the dye adsorbed at TiO center, and its reaction followed the pseudo-first-order kinetics. This mechanism resulted in the formation of more aliphatic amines and/or amide byproducts, which were further transformed to NH4+.