Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO2 phase junction using time-resolved photoluminescence...Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO2 phase junction using time-resolved photoluminescence spectroscopy. Visible （-S00 nm） and near-infrared （NIR, -830 nm） emissions were monitored to give insight into the photoinduced charges of anatase and rutile in the junction, respectively, New fast photoluminescence decay components appeared in the visible emission of futile-phase dominated TiO2 and in the NIR emission of many mixed phase TiO2samples. The fast decays confirmed that the charge separation occurred at the phase junction. The visible emission intensity from the mixed phase TiO2 increased, revealing that charge transfer from rutile to anatase was the main pathway. The charge separation slowed the microsecond time scale photolumines- cence decay rate for charge carriers in both anatase and rutile. However, the millisecond decay of the charge carriers in anatase TiO2 was accelerated, while there was almost no change in the charge carrier dynamics of rutile TiO2. Thus, charge separation at the anatase/rutile phase junction caused an increase in the charge carrier concentration on a microsecond time scale, because of slower electron-hole recombination. The enhanced photocatalytic activity previously observed at ana- tase/rutile phase junctions is likely caused by the improved charge carrier dynamics we report here. These findings may contribute to the development of improved photocatalytic materials.展开更多
In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successf...In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.展开更多
TiO2 nanowire arrays were successfully fabricated by liquid-phase deposition method using porous alumina templates. The obtained TiO2 nanowires were characterized using Raman spectroscopy, X-ray diffraction （XRD）, s...TiO2 nanowire arrays were successfully fabricated by liquid-phase deposition method using porous alumina templates. The obtained TiO2 nanowires were characterized using Raman spectroscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FE- SEM）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） analysis. Results of electron microscopic observations indicated that the nanowires were smooth and uniform with a diameter of about 50-80 nm and several micrometers in length. SAED, Raman, and XRD mea- surements showed that TiO2 nanowires were single-crystalline with a pure rutile structure after heating at 800 ~C for 10 h. In this situation, the nanowire constituents grew preferentially along the 〈001〉 direction. Furthermore, the formation process and mechanistic study of the Ti02 nanowire arrays were proposed and discussed in detail. The nanowires are clearly produced by the deposition of TiO2 particles on the inner wall of the template nanochannels.展开更多
A series of TiO2 with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium nbutoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activi...A series of TiO2 with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium nbutoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activity of the samples was evaluated by degradation of Methyl Orange in aqueous solution under UV-Visible light irradiation. On the basis of detailed analysis of the characterizing results of high-resolution transmission electron microscopy, X-ray powder diffraction measurements, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, it was concluded that the photo-activity of the catalyst is related directly to the 3D morphology and the crystal phase composition. An excellent catalyst should have both a futile 3D flower-like structure and anatase granulous particles. The 3D flower-like structure could enhance light harvesting, as well as the transfer of reactant molecules from bulk solution to the reactive sites on TiO2. In addition, the optimum anatase/rutile phase ratio was found to be 80：20, which is beneficial to the effective separation of the photogenerated electron-hole pairs.展开更多
We report the discovery of TiO_(2)-Ⅱ in the unmelted rock of the shocked Suizhou L6 chondrite.Natural TiO_(2)-Ⅱ was previously found in ultrahigh-pressure metamorphic and mantle-derived rocks,terrestrial impact stru...We report the discovery of TiO_(2)-Ⅱ in the unmelted rock of the shocked Suizhou L6 chondrite.Natural TiO_(2)-Ⅱ was previously found in ultrahigh-pressure metamorphic and mantle-derived rocks,terrestrial impact structures,and tektite.Our microscopic,Raman spectroscopic,electron microprobe and transmission electron microscopic investigations have revealed:(1) All observed TiO_(2)-Ⅱ grains are related with ilmenite and pyrophanite;(2) TiO_(2)-Ⅱ occurs as needle-and leaf-shaped inclusions in llmenite and patch-,tape-shaped body in pyrophanite;(3)The composition of TiO_(2)-Ⅱ is identical with that of its precursor rutile;(4) The Raman spectrum of TiO_(2)-Ⅱ is in good agreement with that of natural and synthesized α-PbO_(2)-type TiO_(2);(5) TiO_(2)-Ⅱ occurs mainly in the form of well-ordered nano-domains and small mis-orientation among the domains can be observed.(6) All electron diffraction reflections from TiO_(2)-Ⅱ can be indexed to α-PbO_(2)structure in space group Pbcn with lattice parameters of a=4.481 ?,b=5.578 A and c=4.921 A;(7) The exsolution inclusions of rutile from host ilmenite are mostly connected with an alternation process along the lamellar twinning plane of ilmenite induced by shockinduced high pressure and high temperature;(8) The P-T regime of 20-25 GPa and 1000 ℃ estimated for the Suizhou unmelted rock is suitable for phase transition of rutile into TiO_(2)-Ⅱ phase.展开更多
All-solid-state Z-scheme photocatalysts,containing Cu_(2)O,TiO_(2)(rutile),and Au as the elec-tron mediator,were prepared and applied to the reduction of Cr(Ⅵ)in aqueous solutions.The Cu_(2)O-Au-TiO_(2) composites we...All-solid-state Z-scheme photocatalysts,containing Cu_(2)O,TiO_(2)(rutile),and Au as the elec-tron mediator,were prepared and applied to the reduction of Cr(Ⅵ)in aqueous solutions.The Cu_(2)O-Au-TiO_(2) composites were prepared by loading Au core-Cu_(2)O shell hemisphere particles on TiO_(2)(rutile)nanorods using a two-step photocatalytic deposition process.Un-der ultraviolet-visible(UV-vis)light illumination,the Cu_(2)O-Au-TiO_(2) composites exhibited higher photocatalytic Cr(Ⅵ)reduction activities than those exhibited by single TiO_(2)(rutile)and Cu_(2)O.In this reaction,a precipitate containing Cr,which was considered to be Cr(OH)_(3),was deposited site-selectively on the Au core-Cu_(2)O shell particles of the composites,indi-cating that the reduction site of the composite was Cu_(2)O,and the reaction proceeded accord-ing to the Z-scheme.The Cu_(2)O-Au-TiO_(2) composites also exhibited photocatalytic activity under visible light illumination.The oxidation state of Cu in the Cu_(2)O-Au-TiO_(2) composite gradually changed from Cu(Ⅰ)to Cu(Ⅱ)during the photocatalytic Cr(Ⅵ)reduction.However the composite maintained its high photocatalytic performance even after oxidation.The role of Au in the Cu_(2)O-Au-TiO_(2) composite was examined by comparing the properties of the Cu_(2)O-Au-TiO_(2) composite with those of the Cu_(2)O-TiO_(2) composite prepared via direct Cu_(2)O deposition on TiO_(2).展开更多
A convenient and scalable technique for the synthesis of rutile titanium dioxide(TiO2) nano-rods was presented by using bulk TiO2 powder, sodium hydroxide(NaOH) and distilled water as raw materials. X-ray diffraction(...A convenient and scalable technique for the synthesis of rutile titanium dioxide(TiO2) nano-rods was presented by using bulk TiO2 powder, sodium hydroxide(NaOH) and distilled water as raw materials. X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) studies indicate that the prepared sample is crystalline and free from any impurities, however, it has no distinct shape and possesses a huge degree of agglomeration, and the average crystal size is around 40 nm. After annealing the sample at 600 °C for 2 h, it is observed through FESEM that nano-rods are formed. And XRD analysis shows that the nano-rods are single crystalline with distinct and smooth surfaces in different sizes with average length of about 1 μm and diameter of about 80 nm. Further UV-visible spectroscopy and Raman studies were conducted for the prepared sample and the band gap of the final product is found to be 3.40 eV.展开更多
The laser ablation technique was employed to prepare TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in the poly-(vinylpyrrolidone) solution using wavelength of 1 064 nm. The as-prepared prod...The laser ablation technique was employed to prepare TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in the poly-(vinylpyrrolidone) solution using wavelength of 1 064 nm. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the rutile TiO2 nanoparticles are synthesized at room temperature and the average size is about 35 nm with narrow size distribution. A possible formation mechanism was discussed and the UV-vis absorption and photoluminescence were measured. The optical study shows that rutile nanoparticle possesses direct optical transition with band gap of 3.15 eV.展开更多
The systematic trends of electrionic structure and optical properties of rutile （P42/mnm） RuO2 have been cal- culated by using the plane-wave norm-conserving pseudopotential density functional theory （DFT） method ...The systematic trends of electrionic structure and optical properties of rutile （P42/mnm） RuO2 have been cal- culated by using the plane-wave norm-conserving pseudopotential density functional theory （DFT） method within the generalised gradient approximation （GGA） for the exchange-correlation potential. The obtained equilibrium structure parameters are in excellent agreement with the experimental data. The calculated bulk modulus and elastic constants are also in good agreement with the experimental data and available theoretical calculations. Analysis based on elec- tronic structure and pseudogap reveals that the bonding nature in RuO2 is a combination of covalent, ionic and metallic bonds. Based on a Kramers Kronig analysis of the reflectivity, we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant （~1 and z2, respectively） and the refractive index （n）; and comparisons have shown that the theoretical results agree well with the experimental data as well. Meanwhile, we have also calculated the absorption coefficient, reflectivity index, electron energy loss function of RuO2 for radiation up to 30 eV. As a result, the predicted reflectivity index is in good agreement with the experimental data at low energies.展开更多
Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials.Carriers can interact with lattices and influence lattice vibrations;thus,it is feasible to study the ...Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials.Carriers can interact with lattices and influence lattice vibrations;thus,it is feasible to study the effect of photo-generated carriers on phonons by analyzing changes in the Raman spectra of semiconductors.Rutile is one of the predominant crystalline phases of TiO_(2),which is a widely utilized metal oxide semiconductor.In this work,rutile TiO_(2) is coated on a thinned optical fiber to concentrate ultraviolet light energy within the material,thereby enhancing the generation of carriers and amplifying the changes in the Raman spectra.A Raman detection laser with a wavelength of 532 nm is utilized to collect the Raman spectra of rutile TiO_(2) during irradiation.Using this setup,the impact of photo-generated carriers on the phonons corresponding to Raman vibrational modes is researched.The localization and non-radiative recombination of photo-generated carriers contribute to a reduction in both the frequencies and lifetimes of phonons.This work provides a novel approach to researching the effect of carriers on phonons.展开更多
The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling ...The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2) on the surface via increasing or decreasing O_(2) exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2) at about 0.1 L O_(2) exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c) species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c) may not change as the exposure of O_(2)changes on the R-TiO_(2)(110) surface,and O_(2) is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2) on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2) on TiO_(2).展开更多
Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild c...Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild conditions,but the detailed reaction mechanism is not well understood.With the surface science approaches,we have studied the adsorption and surface chemistry of cyclohexane on rutile TiO_(2)(110).The thermal desorption spectroscopy and X-ray photoelectron spectroscopy results both demonstrate the molecular adsorption of cyclohexane on rutile TiO_(2)(110).Upon the UV Hg light irradiation,photodesorption of cyclohexane occurs from both the chemisorbed monolayer and the multilayer.No decomposition nor dehydrogenation of cyclohexane occurs on rutile TiO_(2)(110).These results deepen the fundamental understanding of the surface chemistry of cyclohexane on the TiO_(2) surface.展开更多
We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radic...We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radical （CH3.）, ethylene （C2H4）, and methanol （CH3OH） have been detected. The initial step in the decomposition of CH2O on the futile TiO2（100）-（1×1） surface is the formation of a dioxyrnethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4＋ （Tisc） site and its carbonyl C atom bound to a nearby bridge-bonded oxygen （Oh） atom, respectively. During 355 nrn irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO directly, which is considered as the main reaction channel. In addition, the dioxyrnethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Tisc site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the futile TiO2 （100）-（1× 1） surface.展开更多
In this work, structural and optical properties of the TiO2 films deposited on unheated substrates by dual cathode dc unbalanced magnetron sputtering at long substrate-target distance (ds-t) were studied. Titanium dio...In this work, structural and optical properties of the TiO2 films deposited on unheated substrates by dual cathode dc unbalanced magnetron sputtering at long substrate-target distance (ds-t) were studied. Titanium dioxide (TiO2) thin films were deposited on unheated Si (110) wafers, glass slides and carbon coated copper grids at different substrate to target (ds-t) distances. The structural properties of TiO2 thin films were characterized by X-ray diffraction (XRD) and transmission electron microcopy (TEM) with selected-area electron diffraction (SAED), surface morphology using atomic force microscopy (AFM) and optical transmission spectra using a spectrophotometer. XRD results show that TiO2 films deposited at various ds-t distances have only rutile crystal structure. The crystallinity and thickness of the films increased while the roughness decreased with decreasing ds-t distance. The refractive indices of the deposited films were found to be in the range of 2.51 - 2.82 and increased with decreasing ds-t distance.展开更多
Based on first-principles calculations, the electronic and magnetic properties of undoped and Li-doped rutile TiO2 have been studied. The results demonstrate that a cation vacancy can arouse ferromagnetism in TiO2 and...Based on first-principles calculations, the electronic and magnetic properties of undoped and Li-doped rutile TiO2 have been studied. The results demonstrate that a cation vacancy can arouse ferromagnetism in TiO2 and the magnetic moment mainly comes from p orbitals of O atoms around the Ti vacancy. However, the Ti vacancy under normal conditions is very difficult to form due to its high formation energy. Our calculations indicate that Li-doped TiO2 can reduce the formation energy while keeping the magnetism. The large magnetization energy indicates that Li-doped TiO2 is a promising room-temperature diluted magnetic semiconductor.展开更多
基金supported by the National Natural Science Foundation of China (21203185, 21373209)the National Basic Research Program of China (2014CB239400)
文摘Junctions are an important structure that allows charge separation in solar cells and photocatalysts. Here, we studied the charge transfer at an anatase/rutile TiO2 phase junction using time-resolved photoluminescence spectroscopy. Visible （-S00 nm） and near-infrared （NIR, -830 nm） emissions were monitored to give insight into the photoinduced charges of anatase and rutile in the junction, respectively, New fast photoluminescence decay components appeared in the visible emission of futile-phase dominated TiO2 and in the NIR emission of many mixed phase TiO2samples. The fast decays confirmed that the charge separation occurred at the phase junction. The visible emission intensity from the mixed phase TiO2 increased, revealing that charge transfer from rutile to anatase was the main pathway. The charge separation slowed the microsecond time scale photolumines- cence decay rate for charge carriers in both anatase and rutile. However, the millisecond decay of the charge carriers in anatase TiO2 was accelerated, while there was almost no change in the charge carrier dynamics of rutile TiO2. Thus, charge separation at the anatase/rutile phase junction caused an increase in the charge carrier concentration on a microsecond time scale, because of slower electron-hole recombination. The enhanced photocatalytic activity previously observed at ana- tase/rutile phase junctions is likely caused by the improved charge carrier dynamics we report here. These findings may contribute to the development of improved photocatalytic materials.
基金supported by the National Natural Science Foundation of China (21771070, 21571071)the Fundamental Research Funds for the Central Universities (2018KFYYXJJ120, 2019KFYRCPY104)~~
文摘In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.
基金supported by the Institute of Science and High Technology and Environmental Sciences(No.1/1859)
文摘TiO2 nanowire arrays were successfully fabricated by liquid-phase deposition method using porous alumina templates. The obtained TiO2 nanowires were characterized using Raman spectroscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FE- SEM）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） analysis. Results of electron microscopic observations indicated that the nanowires were smooth and uniform with a diameter of about 50-80 nm and several micrometers in length. SAED, Raman, and XRD mea- surements showed that TiO2 nanowires were single-crystalline with a pure rutile structure after heating at 800 ~C for 10 h. In this situation, the nanowire constituents grew preferentially along the 〈001〉 direction. Furthermore, the formation process and mechanistic study of the Ti02 nanowire arrays were proposed and discussed in detail. The nanowires are clearly produced by the deposition of TiO2 particles on the inner wall of the template nanochannels.
基金supported by the National Natural Science Foundation of China(No.20977086,21076196,21177115)the Science and Technology Project of Zhejiang Province,China(No.2012C23026,2011C31041)
文摘A series of TiO2 with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium nbutoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activity of the samples was evaluated by degradation of Methyl Orange in aqueous solution under UV-Visible light irradiation. On the basis of detailed analysis of the characterizing results of high-resolution transmission electron microscopy, X-ray powder diffraction measurements, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, it was concluded that the photo-activity of the catalyst is related directly to the 3D morphology and the crystal phase composition. An excellent catalyst should have both a futile 3D flower-like structure and anatase granulous particles. The 3D flower-like structure could enhance light harvesting, as well as the transfer of reactant molecules from bulk solution to the reactive sites on TiO2. In addition, the optimum anatase/rutile phase ratio was found to be 80：20, which is beneficial to the effective separation of the photogenerated electron-hole pairs.
文摘We report the discovery of TiO_(2)-Ⅱ in the unmelted rock of the shocked Suizhou L6 chondrite.Natural TiO_(2)-Ⅱ was previously found in ultrahigh-pressure metamorphic and mantle-derived rocks,terrestrial impact structures,and tektite.Our microscopic,Raman spectroscopic,electron microprobe and transmission electron microscopic investigations have revealed:(1) All observed TiO_(2)-Ⅱ grains are related with ilmenite and pyrophanite;(2) TiO_(2)-Ⅱ occurs as needle-and leaf-shaped inclusions in llmenite and patch-,tape-shaped body in pyrophanite;(3)The composition of TiO_(2)-Ⅱ is identical with that of its precursor rutile;(4) The Raman spectrum of TiO_(2)-Ⅱ is in good agreement with that of natural and synthesized α-PbO_(2)-type TiO_(2);(5) TiO_(2)-Ⅱ occurs mainly in the form of well-ordered nano-domains and small mis-orientation among the domains can be observed.(6) All electron diffraction reflections from TiO_(2)-Ⅱ can be indexed to α-PbO_(2)structure in space group Pbcn with lattice parameters of a=4.481 ?,b=5.578 A and c=4.921 A;(7) The exsolution inclusions of rutile from host ilmenite are mostly connected with an alternation process along the lamellar twinning plane of ilmenite induced by shockinduced high pressure and high temperature;(8) The P-T regime of 20-25 GPa and 1000 ℃ estimated for the Suizhou unmelted rock is suitable for phase transition of rutile into TiO_(2)-Ⅱ phase.
基金This work was supported by the Japan Society for the Promotion of Science(JSPS)KAKENHI(No.JP 19K05057).
文摘All-solid-state Z-scheme photocatalysts,containing Cu_(2)O,TiO_(2)(rutile),and Au as the elec-tron mediator,were prepared and applied to the reduction of Cr(Ⅵ)in aqueous solutions.The Cu_(2)O-Au-TiO_(2) composites were prepared by loading Au core-Cu_(2)O shell hemisphere particles on TiO_(2)(rutile)nanorods using a two-step photocatalytic deposition process.Un-der ultraviolet-visible(UV-vis)light illumination,the Cu_(2)O-Au-TiO_(2) composites exhibited higher photocatalytic Cr(Ⅵ)reduction activities than those exhibited by single TiO_(2)(rutile)and Cu_(2)O.In this reaction,a precipitate containing Cr,which was considered to be Cr(OH)_(3),was deposited site-selectively on the Au core-Cu_(2)O shell particles of the composites,indi-cating that the reduction site of the composite was Cu_(2)O,and the reaction proceeded accord-ing to the Z-scheme.The Cu_(2)O-Au-TiO_(2) composites also exhibited photocatalytic activity under visible light illumination.The oxidation state of Cu in the Cu_(2)O-Au-TiO_(2) composite gradually changed from Cu(Ⅰ)to Cu(Ⅱ)during the photocatalytic Cr(Ⅵ)reduction.However the composite maintained its high photocatalytic performance even after oxidation.The role of Au in the Cu_(2)O-Au-TiO_(2) composite was examined by comparing the properties of the Cu_(2)O-Au-TiO_(2) composite with those of the Cu_(2)O-TiO_(2) composite prepared via direct Cu_(2)O deposition on TiO_(2).
基金the Ministry of Science and Technology of China，the 'Strategic Priority Research Program' of the Chinese Academy of Sciences，the National Natural Science Foundation of China
基金supported by the MKE (The Ministry of Knowledge Economy)Korea Under the ITRC (Information Technology Research Centre) support program supervised by the NIPA (National IT industry Promotion Agency) (NIPA-2012-H0301-12-2009)+1 种基金supported by the Ministry of Education, Science and Technology (MEST)National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation (2012H1B8A2026212)
文摘A convenient and scalable technique for the synthesis of rutile titanium dioxide(TiO2) nano-rods was presented by using bulk TiO2 powder, sodium hydroxide(NaOH) and distilled water as raw materials. X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) studies indicate that the prepared sample is crystalline and free from any impurities, however, it has no distinct shape and possesses a huge degree of agglomeration, and the average crystal size is around 40 nm. After annealing the sample at 600 °C for 2 h, it is observed through FESEM that nano-rods are formed. And XRD analysis shows that the nano-rods are single crystalline with distinct and smooth surfaces in different sizes with average length of about 1 μm and diameter of about 80 nm. Further UV-visible spectroscopy and Raman studies were conducted for the prepared sample and the band gap of the final product is found to be 3.40 eV.
基金Project(09R23) supported by the Scientific Research Starting Foundation of Nantong UniversityProjects(50671100, 10604055) supported by the National Natural Science Foundation of China
文摘The laser ablation technique was employed to prepare TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in the poly-(vinylpyrrolidone) solution using wavelength of 1 064 nm. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the rutile TiO2 nanoparticles are synthesized at room temperature and the average size is about 35 nm with narrow size distribution. A possible formation mechanism was discussed and the UV-vis absorption and photoluminescence were measured. The optical study shows that rutile nanoparticle possesses direct optical transition with band gap of 3.15 eV.
基金supported by the China Scholarship Council (CSC) and the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)the Science-Technology Foundation for Young Scientist of Sichuan Province,China (Grant No. 09ZQ026-049)
文摘The systematic trends of electrionic structure and optical properties of rutile （P42/mnm） RuO2 have been cal- culated by using the plane-wave norm-conserving pseudopotential density functional theory （DFT） method within the generalised gradient approximation （GGA） for the exchange-correlation potential. The obtained equilibrium structure parameters are in excellent agreement with the experimental data. The calculated bulk modulus and elastic constants are also in good agreement with the experimental data and available theoretical calculations. Analysis based on elec- tronic structure and pseudogap reveals that the bonding nature in RuO2 is a combination of covalent, ionic and metallic bonds. Based on a Kramers Kronig analysis of the reflectivity, we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant （~1 and z2, respectively） and the refractive index （n）; and comparisons have shown that the theoretical results agree well with the experimental data as well. Meanwhile, we have also calculated the absorption coefficient, reflectivity index, electron energy loss function of RuO2 for radiation up to 30 eV. As a result, the predicted reflectivity index is in good agreement with the experimental data at low energies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52122008,51978024,and 52370003)the Science and Technology and Innovation Commission of Shen Zhen Municipality(Grant No.JCYJ20200109105212568).
文摘Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials.Carriers can interact with lattices and influence lattice vibrations;thus,it is feasible to study the effect of photo-generated carriers on phonons by analyzing changes in the Raman spectra of semiconductors.Rutile is one of the predominant crystalline phases of TiO_(2),which is a widely utilized metal oxide semiconductor.In this work,rutile TiO_(2) is coated on a thinned optical fiber to concentrate ultraviolet light energy within the material,thereby enhancing the generation of carriers and amplifying the changes in the Raman spectra.A Raman detection laser with a wavelength of 532 nm is utilized to collect the Raman spectra of rutile TiO_(2) during irradiation.Using this setup,the impact of photo-generated carriers on the phonons corresponding to Raman vibrational modes is researched.The localization and non-radiative recombination of photo-generated carriers contribute to a reduction in both the frequencies and lifetimes of phonons.This work provides a novel approach to researching the effect of carriers on phonons.
基金This work was supported by the National Natural Science Foundation of China(No.21973010)Liaoning Revitalization Talents Program(No.XLYC1907032)The authors thank Qing Guo at Southern University of Science and Technolog for many insightful discussions。
文摘The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2) on the surface via increasing or decreasing O_(2) exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2) at about 0.1 L O_(2) exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c) species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c) may not change as the exposure of O_(2)changes on the R-TiO_(2)(110) surface,and O_(2) is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2) on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2) on TiO_(2).
基金This work is supported by the National Natural Science Foundation of China(No.22202191).
文摘Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild conditions,but the detailed reaction mechanism is not well understood.With the surface science approaches,we have studied the adsorption and surface chemistry of cyclohexane on rutile TiO_(2)(110).The thermal desorption spectroscopy and X-ray photoelectron spectroscopy results both demonstrate the molecular adsorption of cyclohexane on rutile TiO_(2)(110).Upon the UV Hg light irradiation,photodesorption of cyclohexane occurs from both the chemisorbed monolayer and the multilayer.No decomposition nor dehydrogenation of cyclohexane occurs on rutile TiO_(2)(110).These results deepen the fundamental understanding of the surface chemistry of cyclohexane on the TiO_(2) surface.
基金supported by the National Natural Science Foundation of China(No.21673235 and No.21403224)the Youth Innovation Promotion Association CAS,and the Key Research Program of the Chinese Academy of Sciences
文摘We have investigated the photoinduced decomposition of formaldehyde （CH2O） on a rutile TiO2（100）-（1×1） surface at 355 nrn using ternperature-prograrnrned desorption. Products, formate （HCOO）, methyl radical （CH3.）, ethylene （C2H4）, and methanol （CH3OH） have been detected. The initial step in the decomposition of CH2O on the futile TiO2（100）-（1×1） surface is the formation of a dioxyrnethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4＋ （Tisc） site and its carbonyl C atom bound to a nearby bridge-bonded oxygen （Oh） atom, respectively. During 355 nrn irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO directly, which is considered as the main reaction channel. In addition, the dioxyrnethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Tisc site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the futile TiO2 （100）-（1× 1） surface.
文摘In this work, structural and optical properties of the TiO2 films deposited on unheated substrates by dual cathode dc unbalanced magnetron sputtering at long substrate-target distance (ds-t) were studied. Titanium dioxide (TiO2) thin films were deposited on unheated Si (110) wafers, glass slides and carbon coated copper grids at different substrate to target (ds-t) distances. The structural properties of TiO2 thin films were characterized by X-ray diffraction (XRD) and transmission electron microcopy (TEM) with selected-area electron diffraction (SAED), surface morphology using atomic force microscopy (AFM) and optical transmission spectra using a spectrophotometer. XRD results show that TiO2 films deposited at various ds-t distances have only rutile crystal structure. The crystallinity and thickness of the films increased while the roughness decreased with decreasing ds-t distance. The refractive indices of the deposited films were found to be in the range of 2.51 - 2.82 and increased with decreasing ds-t distance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11005049 and 61006051)
文摘Based on first-principles calculations, the electronic and magnetic properties of undoped and Li-doped rutile TiO2 have been studied. The results demonstrate that a cation vacancy can arouse ferromagnetism in TiO2 and the magnetic moment mainly comes from p orbitals of O atoms around the Ti vacancy. However, the Ti vacancy under normal conditions is very difficult to form due to its high formation energy. Our calculations indicate that Li-doped TiO2 can reduce the formation energy while keeping the magnetism. The large magnetization energy indicates that Li-doped TiO2 is a promising room-temperature diluted magnetic semiconductor.
