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Borse, P.H.,Cho, C.R.,Yu, S.M.,Yoon, J.H.,Hong, T.E.,Bae, J.S.,Jeong, E.D.,Kim, H.G. Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.10
The Ti incorporation at Fe-site in the double perovskite lattice of $Sr_2FeNbO_6$ (SFNO) system is studied. The Ti concentration optimization yielded an efficient photocatalyst. At an optimum composition of Ti as x = 0.07 in $Sr_2Fe_{1-x}Ti_xNbO_6$, the photocatalyst exhibited 2 times the quantum yield for photolysis of $H_2O$ in presence of $CH_3OH$, than its undoped counterpart under visible light (${\lambda}{\geq}420nm$). Heavily Ti-doped $Sr_2Fe_{1-x}Ti_xNbO_6$ lattice exhibited poor photochemical properties due to the existence of constituent impurity phases as observed in the structural characterization, as well as deteriorated optical absorption. The higher electron-density acquired by n-type doping seem to be responsible for the more efficient charge separation in $Sr_2Fe_{1-x}Ti_xNbO_6$ (0.05 < x < 0.4) and thus consequently displays higher photocatalytic activity. The Ti incorporated structure also found to yield stable photocatalyst.
Borse, Pramod H.,Yoon, Sang-Su,Jang, Jum-Suk,Lee, Jae-Sung,Hong, Tae-Eun,Jeong, Euh-Duck,Won, Mi-Sook,Jung, Ok-Sang,Shim, Yoon-Bo,Kim, Hyun-Gyu Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12
Structural and thermo-analytical studies were carried out to understand the phase formation kinetics of the single phase $Bi_5Ti_3FeO_{15}$ (BTFO) nanocrystals in $Bi_2O_3-Fe_2O_3-TiO_2$, during the polymerized complex (PC) synthesis method. The crystallization of Aurivillius phase $Bi_5Ti_3FeO_{15}$ layered perovskite was found to be initiated and achieved under the temperature conditions in the range of ${\sim}$800 to 1050$^{\circ}C$. The activation energy for grain growth of $Bi_5Ti_3FeO_{15}$ nanocrystals (NCs) was very low in case of NCs formed by PC (2.61 kJ/mol) than that formed by the solid state reaction (SSR) method (10.9 kJ/mol). The energy involved in the phase transformation of Aurivillius phase $Bi_5Ti_3FeO_{15}$ from $Bi_2O_3-Fe_2O_3-TiO_2$ system was ${\sim}$ 69.8 kJ/mol. The formation kinetics study of $Bi_5Ti_3FeO_{15}$ synthesized by SSR and PC methods would not only render a large impact in the nanocrystalline material development but also in achieving highly efficient visible photocatalysts.
Pramod H. Borse,김현규,조채용,K. T. Lim,홍태은,정의덕,J.H. Yoon,S.M. Yu 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.1
Zn2TiO4 a spinel-type structure photocatalyst, was synthesized by a solid-state reaction method, and obtained as a single phase in the temperature range of 900-1200 oC. The average particle size for case of the as-synthesized Zn2TiO4 sample, sintered at 1200 oC was found to be 5 μm, whereas it lay in the range of 0.5-2 μm for the case of TiO2 calcined at 650 oC. The band gap of Zn2TiO4 and TiO2 (rutile) samples determined by UV-Vis diffuse reflectance spectra (DRS) was 3.10 eV (400 nm). The Zn2TiO4 sample calcined at 1200 oC exhibited a higher hydrogen production rate than that of rutile TiO2 from a watermethanol mixture under UV (λ ≥ 210 nm) and near-visible (μ ≥ 400 nm) light irradiation. In spite of having the same bandgap energy, the photocatalytic activity of Zn2TiO4 was found to be higher than that of rutile TiO2, manily because of its more negative conduction band edge than rutile TiO2.
P. H. Borse,장점석,S. J. Hong,이재성,정종현,T. E. Hong,안창원,정의덕,K. S. Hong,J. H. Yoon,김현규 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.4
A spinel crystal structure of ferrite containing zinc (ZnFe2O4) was synthesized by using the polymer complex method. A pure phase ZnFe2O4 was obtained at a relatively lower temperature of 900˚C. The as-synthesized nanoparticles are agglomerates of crystals with an average size of ∼50 nm, as estimated from the X-ray diffraction analysis. The band gap of the n-type semiconducting metal oxide, as determined by using an ultraviolet-visible diffuse reflectance spectrometer was found to be 1.90 eV (653 nm). The photocatalytic activity of ZnFe2O4 was investigated by using the photoreduction of water under visible light (≥420 nm), which was found to be much higher than that of the well-known TiO2−xNx photocatalyst. This superior performance is attributed to the larger surface area, the uniform and well-dispersed deposition of the Pt co-catalyst over the surface, and the small band gap of the chemically-prepared ferrite photocatalyst.
Synthesis of Barium Ferrite for Visible Light Photocatalysis Applications
P. H. Borse,조채룡,K. T. Lim,Y. J. Lee,T. E. Hong,J. S. Bae,정의덕,김해진,H. G. Kim,조채용 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.6
Orthorhombic phase BaFe_2O_4 powder was synthesized by using a solid state reaction method and investigated for its visible light photocatalytic properties. The crystallization of the structural phase was found to occur at a temperature above 1000 ℃ yielding a pure orthorhombic phase BaFe_2O_4 (SG- B b21m) at 1100 ℃. The estimated band gap, as determined by UV-Vis diffuse reflectance studies, was ∼1.9 eV (652 nm). A new material was designed and fabricated as Pt/RuO_2/BaFe_2O_4 to enhance its photocatalytic activity. A very low (<1 wt% RuO_2) co-catalyst doping over BaFe_2O_4 was important for achieving high photocatalytic efficiency. The newly designed system was investigated for photo-decomposition of isopropyl alcohol (IPA) and of water under visible light (≥420 nm). Its photocatalytic activity was significantly higher than that of platinized TiO_(2−x)N_x. A mechanism has been proposed to explain the photocatalytic behavior of the designed BaFe_2O_4 photocatalyst.
Pramod H. Borse,김재영,이재성,임권택,정의덕,배종성,윤장희,Seong Mi Yu,김현규 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.1
The effect substitution of Ti<sup>4+</sup> at the Fe<sup>3+</sup> site in a CaFe<sub>2</sub>O<sub>4</sub>/MgFe<sub>2</sub>O<sub>4</sub> bulk hetero-junction (BH) lattice photocatalyst was explored and the Ti ion concentration was optimized to fabricate an efficient photocatalyst. A BH consisting of an optimum dopant concentration (Ti<sup>+4</sup>) level of <i>x</i> = 0.03 exhibited an increased band gap and generated a 1.5 times higher photocurrent. The newly fabricated Ti ion doped photocatalyst showed an enhanced quantum yield (upto ∼13.3%) for photodecomposition of a H<sub>2</sub>O-CH<sub>3</sub>OH mixture, as compared to its undoped BH counterpart under visible light (λ ≥ 420 nm). In contrast, the material doped with a very high Ti-dopant concentration displayed deteriorated photochemical properties. An efficient charge-separation induced by Ti-ion doping seems to be responsible for the higher photocatalytic activity in a doped bulk BH.
Pramod H. Borse,김현규,장점석,이재성,F. Nawaz Khan,하명규,김종필,배종성,정의덕 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4
The substitution effect of Ti^(4+) at Fe^(3+) site in ZnFe_2O_4, a spinel-phase system, has been studied and further optimized to fabricate an efficient photocatalyst. The material doped with electron donor (Ti^(+4)), ZnFe_(2−x)Ti_xO_4 with an optimum composition of x=0.06 exhibited a unchanged band gap, but generated two times higher photocurrent, and showed enhanced quantum yield (upto 0.77%) for photodecomposition of H_2O-CH_3OH mixture, than undoped material under visible light ((λ≥420 nm). In contrast, the material doped with very high concentration of Ti revealed deteriorated photochemical properties due to constituent impurity phases. The higher electron density by n-type doping seems to be responsible for the more efficient charge separation in ZnFe_(2−x)Ti_xO_4 (0.01 < x < 0.09), and hence, the high photocatalytic activity.
Pramod H. Borse,조채용,K. T. Lim,Y. J. Lee,배종성,정의덕,H. G. Kim 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1
We synthesized four different photocatalyst systems viz. Zn_2TiO_4, Zn_2Ti_(1-x)Fe_xO_4, Zn_2Ti_(1-x)Cr_xO_4 (0 ≤ x < 0.8) and Zn_2Ti_(0.9)Cr_yFe_([0.1]-y)O_4 (0.022TiO<SUB>4</SUB> was converted to visible light active material by controlled doping/co-doping of Cr and Fe metal-ions at Ti substitutional site. We investigated their structural, optical and photocatalytic water decomposition property. The co-doping induces strong absorption bands in visible region (at λ~ 480 nm and λ~ 620 nm) in the host band gap. The optimum system of Zn_2Ti_(0.9)Cr_(0.05)Fe_(0.05)O_4 yielded maximum H<SUB>2</SUB> generation. In contrast to the visible light inactivity of Fe and Cr doped Zn_2TiO_4, the H_2 production under visible light irradiation from co-doped samples, increased till the optimum ‘y’ value. Consequently, there exists an optimized co-dopant concentration for efficient photocatalytic hydrogen production under visible light (λ ≥ 420 nm).
Pramod H. Borse,조채용,K. T. Lim,배종성,정의덕,홍태은,김해진,H.G. Kim 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5
We studied the Crx/Fe1−x (0.2 ≤ x ≤ 0.8) co-dopant ratio dependence on the visible light activity of TiO2 : [Cr-Fe] nanoparticles for photodecomposition of gaseous iso-propyl alcohol (IPA), as well as photo reduction of water. Nanoparticles of TiO2 :[CrxFe1−x] with an optimum value of x = 0.4 generated 2-4 times higher photocurrents. The optimum concentration shows maximum photodecomposition activity for IPA, as well as photocatalytic hydrogen generation under visible light (λ > 420 nm). The study on the ratio optimization of the co-dopant metals ions was found to be an important factor for devising an efficient photocatalyst. The optimum co-dopant ratio seems to yield favorable density of states in the band gap of TiO2, which otherwise would turn into recombination centers.