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    Boron modified Ag3PO4 powders for UV and visible light photocatalytic degradation of various dyes
    (Taylor & Francis Inc, 2024) Erzin, Kubilay; Yurtsever, Husnu Arda
    Pure and boron modified Ag3PO4 powders with different boron contents (0-5 wt.%) were prepared. XRD, ATR-FTIR, XPS, SEM-EDX, UV-Vis DRS and PL analyses were conducted for the characterization of the prepared powders. Characterization studies indicated the reduction in the band gap energy, the presence of boron and no change in the morphology due to boron modification. The results of photocatalytic experiments showed that boron modification increased the activity of Ag3PO4. The UV light dye degradation efficiency increased from 63% to 84% for methyl orange (MO) and from 41% to 65% for methyl red by 3% boron modification. The reaction rate constant for MO increased by a factor of 1.7. Under visible light, the activity was similarly enhanced by boron modification. The photocatalytic degradation efficiency increased from 31% to 58% and the reaction rate constant increased by a factor of 2.3 by boron modification for MO under low intensity visible light. These results showed that boron modification enhanced the photocatalytic dye degradation activity of Ag3PO4 under both UV and visible light. This enhancement was attributed to the decrease in the band gap energy and the increase in the interaction of the dye molecules with the photocatalyst surface through boron species. [GRAPHICS]
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    Fabrication of ZIF-8 decorated copper doped TiO2 nanocomposite at low ZIF-8 loading for solar energy applications
    (Elsevier, 2021) Yurtsever, Husnu Arda; Cetin, Ali Emrah
    The effects of crystallization time and amount of Zeolitic Imidazolate Framework-8 (ZIF-8) on the photocatalytic activity of ZIF-8 decorated copper (Cu) doped titania (TiO2) (ZIF-8/Cu-TiO2) powders were investigated in this study. The formation of nanocomposite structure of ZIF-8 crystals grown over the surface of core Cu-TiO2 particles containing heterojunction sites was observed at low ZIF-8 level. Powders containing ZIF-8 in the 5-46% range (weight basis) were synthesized and their activities in the photocatalytic degradation of an organic dye molecule were evaluated. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) analyses indicated that ZIF-8/Cu-TiO2 nanocomposite can be prepared at low levels of ZIF-8. HR-TEM images of 46% ZIF-8/Cu-TiO2 showed that Cu-TiO2 particles act as a core and ZIF-8 crystals grow over the surface of Cu-TiO2 particles during crystal growth and Cu-TiO2 particles were almost completely covered with ZIF-8 crystals. Photocatalytic activity increased with decreasing ZIF-8 level which was attributed to the formation of heterojunctions due to partial coverage of TiO2 surface. The 1st order reaction rate constant of ZIF-8/Cu-TiO2 nanocomposite containing 5% ZIF-8 was found to be 4 and 1.4 times that of bare ZIF-8 and CuTiO2, respectively. Partial coverage of TiO2 surface with ZIF-8 crystals lead to the formation of light exposed ZIF8/Cu-TiO2 heterojunction sites for the enhanced degradation of the dye molecule. The presence of ZIF-8 in the nanocomposite also increased the adsorption of the organic dye by the interaction with open Zn2+ metal sites of ZIF-8 on the nanocomposite surface. This study revealed that ZIF-8/Cu-TiO2 nanocomposites could be prepared at low ZIF-8 levels and short growth times with higher photocatalytic activities than their constituents and nanocomposites prepared at higher ZIF-8 levels and longer growth times.
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    Impact of titania phase structure and surface reactivity on the photocatalytic degradation of various dyes and textile wastewater
    (Natl Inst Science Communication-Niscair, 2023) Yurtsever, Husnu Arda; Iloglu, Onur; ciftcioglu, Muhsin
    Titania (TiO2) powders have been prepared by precipitation method in different precipitation media which contain sulfate, nitrate or organic species. Photocatalytic degradation of different dyes and a real textile wastewater have been conducted with these powders along with commercial powder Degussa P25 for comparison. Ethyl alcohol (organic medium), sulfuric acid (sulfate medium) and nitric acid (nitrate medium) have been used to dissolve titanium precursor for the precipitation of TiO2 in ammonia solution. UV-Vis DRS and XPS results indicate that S doping in sulfate medium precipitated powder and N doping in nitrate medium precipitated powder has been occurred and the presence of S or N containing impurities on the grain boundaries have been improved light absorption of TiO2 significantly. However, these powders have exhibited low surface reactivities. The highest surface reactivity has been obtained with the powder precipitated in organic medium which also has the highest crystallite sizes (76 nm rutile and 34 nm anatase crystallites) with relatively low rutile weight percentage (10.0%). The surface-normalized rate constants of this powder are 0.02038 min-1.m-2 in real textile wastewater degradation and 0.0161 min-1.m-2 in methyl orange degradation, which are 0.01563 and 0.0091 min-1.m-2, respectively, for Degussa P25. Results have shown that this powder show 30-70% higher surface reactivities compared to Degussa P25. The main structural difference of organic medium precipitated powder and Degussa P25 has been found to be the anatase-rutile weight ratio and crystallite size of rutile phase whereas band gap energy of Degussa P25 is lower and other properties are not significantly different.
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    Inverse effects of lanthanide co-doping on the photocatalytic hydrogen production and dye degradation activities of Cu doped sol-gel TiO2
    (Elsevier, 2023) Yurtsever, Husnu Arda; Erzin, Kubilay; Ciftcioglu, Muhsin
    Copper doped and lanthanide-copper co-doped titania powders were prepared by sol-gel technique and the effects of co-doping on the photocatalytic reduction and oxidation activities of titania were investigated in this work. Characterization studies indicated that a reduced structure was formed due to the presence of Ti3+ species in copper doped titania powder and a more stable structure was formed when lanthanides were used as co-dopants. Copper doped powder had a significantly higher activity in photocatalytic hydrogen production (1037 mu mol/g/h) than the co-doped powders (similar to 400 mu mol/g/h). The oxidation activities of co-doped powders however were determined to be about 2 times higher than that of the copper doped powder. The decrease in the reduction activity was attributed to the decrease in the number of Ti3+ sites, whereas the increase in oxidation activity was probably a result of the increase in the surface area and dye adsorption due to lanthanide co-doping.
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    The effect of powder preparation method on the artificial photosynthesis activities of neodymium doped titania powders
    (Pergamon-Elsevier Science Ltd, 2018) Yurtsever, Husnu Arda; Ciftcioglu, Muhsin
    The effects of nanostructure on the artificial photosynthesis activities of undoped and Nd doped titania (TiO2) powders prepared by three different chemical co-precipitation methods were investigated. Substitutional/interstitial N and S doping was observed in powders due to the presence of high concentrations of HNO3 (NP) and H2SO4 (SP) in the powder preparation media, respectively. Nd, N and S doping caused anatase/rutile phase transformation inhibition and crystallite size reduction in the nanostructure. Light absorption was significantly enhanced by Nd doping and the residual SO42-/NOx species in the nanostructure. Photocatalytic hydrogen production activity of Nd doped NP powder was 4 times greater than undoped NP powder at 700 degrees C and had a high purity (CO:H-2 ratio similar to 0.00). CO was determined to be the main product in photocatalytic CO2 reduction. NP powders had the highest CO yields and Nd doping enhanced CO production. The powders with high crystallite sizes and rutile weight fractions had the highest artificial photosynthesis activities. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    The effects of annealing temperature on the thickness, morphology, band gap energy, and photocatalytic performance of ZIF-8-derived ZnO/TiO2 thin films
    (Springer, 2024) Iloglu, Onur; Yurtsever, Husnu Arda
    Multi-oxide photocatalytic materials derived from metal organic frameworks (MOFs) are attracting widespread attention in recent years. The heterostructure originating from oxide-oxide junctions and nonmetal doping due to the combustion of organics from MOFs provide desirable properties to the photocatalytic material. In this study, the effects of annealing temperature on the material properties and photocatalytic activity of ZIF-8-derived ZnO/TiO2 thin films were investigated. XRD, XPS, and FTIR analyses confirmed the oxidation of ZIF-8 to ZnO and SEM analysis revealed the formation of a porous structure at the annealing temperature of 500 degrees C. UV-Vis analysis indicated that the band gap energy decreased from 3.23 to 2.04 eV with increasing annealing temperature. Photocatalytic methylene blue degradation experiments showed that the thin film annealed at 500 degrees C had higher activity than the films annealed at lower temperatures. The thin film annealed at 500 degrees C had more than two times the dye degradation efficiency of the film annealed at 400 degrees C (72% and 33%, respectively). This film was also active in the photocatalytic degradation of caffeic acid which is a colorless pollutant. The high photocatalytic activity of the thin film annealed at higher temperature was attributed to its narrower band gap energy, higher porosity, and more efficient electron-hole separation, which are due to the presence of heterostructure, nonmetal doping, and deficient zones formed by the oxidation of imidazole rings.