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
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
Uniquely structured rutile TiO2 microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 ℃ for 2 h, the futile TiO2 microsp...Uniquely structured rutile TiO2 microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 ℃ for 2 h, the futile TiO2 microspheres with a high surface area of 132 m2/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells （DSSCs）. The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO2 photoanodes made of futile TiO2 microspheres and anatase TiO, nanoparticles （mass ratio of 1：1）, significantly higher than that of pure anatase TiO2 nanoparticle photoanodes of similar thickness （6.74%）. Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of futile TiO2 microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes （450-800 nm） to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular futile single crystals phases giving high electron collection efficiency.展开更多
Li4Ti5O12 is considered as a safe and stable anode material for high-power lithium-ion batteries due to its“zero-strain”characteristic during the charge/discharge.However,the intrinsically low electronic conductivit...Li4Ti5O12 is considered as a safe and stable anode material for high-power lithium-ion batteries due to its“zero-strain”characteristic during the charge/discharge.However,the intrinsically low electronic conductivity leads to a deterioration in highrate performance,impeding its intensive application.Herein,the Li4Ti5O12/rutile TiO2(LTO/RT)heterostructured nanorods with tunable oxide phases have been in-situ fabricated by annealing the electrospun nanofiber precursor.By constructing such a heterostructured interface,the as-prepared sample delivers a high capacity of 160.3 mAh·g–1 at 1 C after 200 cycles,125.5 mAh·g–1 at 10 C after 500 cycles and a superior capacity retention of 90.3%after 1,000 cycles at 30 C,outperforming the heterostructure-free counterparts of pure LTO,RT and the commercial LTO product.Density Functional Theory calculation suggests a possible synergistic effect of the LTO/RT interface that would improve the electronic conductivity and Li-ion diffusion.展开更多
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 view of the high activity of Pt single atoms in the low-temperature oxidation of CO,we investigate the adsorption behavior of Pt single atoms on reduced rutile TiO2(110)surface and their interaction with CO and O2 ...In view of the high activity of Pt single atoms in the low-temperature oxidation of CO,we investigate the adsorption behavior of Pt single atoms on reduced rutile TiO2(110)surface and their interaction with CO and O2 molecules using scanning tunneling microscopy and density function theory calculations.Pt single atoms were prepared on the TiO2(110)surface at 80 K,showing their preferred adsorption sites at the oxygen vacancies.We characterized the adsorption configurations of CO and O2 molecules separately to the TiO2-supported Pt single atom samples at 80 K.It is found that the Pt single atoms tend to capture one CO to form Pt-CO complexes,with the CO molecule bonding to the fivefold coordinated Ti(Ti5 c)atom at the next nearest neighbor site.After annealing the sample from 80 K to 100 K,CO molecules may diffuse,forming another type of complexes,Pt-(CO)2.For O2 adsorption,each Pt single atom may also capture one O2 molecule,forming Pt-O2 complexes with O2 molecule bonding to either the nearest or the next nearest neighboring Ti5c sites.Our study provides the single-molecule-level knowledge of the interaction of CO and O2 with Pt single atoms,which represent the important initial states of the reaction between CO and O2.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
TiO2/Nb2O5 photocatalyst loaded with WO3 （WO3-TiO2/Nb2O5） was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse ...TiO2/Nb2O5 photocatalyst loaded with WO3 （WO3-TiO2/Nb2O5） was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiOjNb2O5 by using Fe^3＋ as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 μmol/（L·h）.展开更多
We report the synthesis of TiO2/ZnSn（OH）6 as a novel nano-composite material via a simultaneous crystallization-etching route with cubic nano-ZnSn（OH）6 and TiF4 as the precursors. The structure, composition and mo...We report the synthesis of TiO2/ZnSn（OH）6 as a novel nano-composite material via a simultaneous crystallization-etching route with cubic nano-ZnSn（OH）6 and TiF4 as the precursors. The structure, composition and morphology of the composite were characterized by XRD, EDS, FETEM and FESEM, which showed the prepared TiO2/ZnSn（OH）6 had a unique morphology of hollow cubic nano-ZnSn（OH）6 attached with rutile TiO2 nanoparticles. The results of photocatalytic activity measurement indicated the photocatalytic activity of the prepared composite was better than that of nano-ZnSn（OH）6. This study may be helpful for the design and fabrication of functional comoosite materials.展开更多
Titanium dioxide（TiO2） is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO2 have been found to exhibit different...Titanium dioxide（TiO2） is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO2 have been found to exhibit different photo-activities, though the origins are still not fully understood. In this work, we use the density functional theory（DFT） calculations, corrected by on-site Coulomb and long-range dispersion interactions, to study the adsorptions of nitric oxide（NO） and oxygen（O2） molecules on the clean and hydrogenated anatase TiO2（101） surfaces. We also compare the detailed calculated results regarding their structural, energetic and electronic properties with those obtained at rutile TiO2（110）. It has been found that the behaviors of the surface localized electrons being transferred from adsorbed H, as well as the adsorption behaviors of NO and O2 are quite different at the two surfaces, which can be attributed to their characteristic local bonding structures around the surface hydroxyl. These results may also help explain the different photocatalytic activities of these two main facets of anatase and rutile TiO2展开更多
The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 btm 2 in areal density were prepared by the hydrothermal method to replace the typical 200-300 nm thick mesoporous TiO2 thin films in pe...The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 btm 2 in areal density were prepared by the hydrothermal method to replace the typical 200-300 nm thick mesoporous TiO2 thin films in perovskite solar cells. The CH3NH3PbI3 xBrx capping layers with different thicknesses were obtained on the TiO2 nanorod arrays using different concentration PbI2.DMSO complex precursor solutions in DMF and the photovoltaic performances of the corresponding solar cells were compared. The perovskite solar cells based on 240 nm long TiO2 nanorod arrays and 420 nm thick CH3NH3PbI3 xBrx capping layers showed the best photoelectric conversion efficiency （PCE） of 15.56% and the average PCE of 14.93 ± 0.63% at the relative humidity of 50%-54% under the illumination of simulated AM 1.5 sunlight （100 mW.cm-2）.展开更多
Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, wit...Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 e V, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO（2.07%） exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h-1, which is about four times as high as that of the pristine one（185 μmol h-1）. The presence of VOelevates the apparent Fermi level of rutile TiO2 and promotes the efficient electronhole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time（7.6×103 ns） of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.展开更多
Traditionally, we use a slab to mimic a surface and we constrain the slab to have the bulk-terminated 2D lattice constants. Here we propose a different model in which we impose no constraints, allowing all coordinates...Traditionally, we use a slab to mimic a surface and we constrain the slab to have the bulk-terminated 2D lattice constants. Here we propose a different model in which we impose no constraints, allowing all coordinates including the 2D slab itself to relax. We perform DFT calculations on both models. We find that the unconstrained slabs yield better agreement with experimental results and they have lower total energies. The optimized 2D lattice constants of the unconstrained slabs eventually converge to the attached bulk value. The total energy difference reveals that, with odd number trilayers, the unconstrained slab is much closer to the corresponding constrained slab. The surface energies both converge to the individual values with the number of atomic layers.展开更多
Photodegradation of benzene at ppb levels by mixed-phase TiO2 nanoparticles, synthesized by the oxidation of TiCl4 in propane/air turbulent flame chemical vapor deposition （CVD） process, is investigated experimental...Photodegradation of benzene at ppb levels by mixed-phase TiO2 nanoparticles, synthesized by the oxidation of TiCl4 in propane/air turbulent flame chemical vapor deposition （CVD） process, is investigated experimentally by using a tubular photoreactor with thin TiO2 films coated on the reactor wall by sedimentation. Effects of inlet benzene concentration from 10 to 300μg/m3, rutile mass fraction from about 20 to 50% and photoluminescence （PL） intensity of TiO2 nanoparticles on degradation degree are examined under the conditions of 70% relative humidity, 38 μg/cm2 catalyst loading, 24mW/cm2 UV irradiation of 254 nm and 5.7 s residence time in the reactor. Based on experimental results, separation of photoinduced electron （e-） and hole （h＋） pairs by rutile phase is discussed as photo-induced electron （e-） in anatase phase will migrate to rutile surface due to that the potential of conductive band of rutile is lower than that of anatase, leading to more holes ready on anatase surface for oxidation reactions.展开更多
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 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Uniquely structured rutile TiO2 microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 ℃ for 2 h, the futile TiO2 microspheres with a high surface area of 132 m2/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells （DSSCs）. The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO2 photoanodes made of futile TiO2 microspheres and anatase TiO, nanoparticles （mass ratio of 1：1）, significantly higher than that of pure anatase TiO2 nanoparticle photoanodes of similar thickness （6.74%）. Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of futile TiO2 microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes （450-800 nm） to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular futile single crystals phases giving high electron collection efficiency.
基金This work was financially supported by the National Key R&D Program of China(No.2021YFB2401900).
文摘Li4Ti5O12 is considered as a safe and stable anode material for high-power lithium-ion batteries due to its“zero-strain”characteristic during the charge/discharge.However,the intrinsically low electronic conductivity leads to a deterioration in highrate performance,impeding its intensive application.Herein,the Li4Ti5O12/rutile TiO2(LTO/RT)heterostructured nanorods with tunable oxide phases have been in-situ fabricated by annealing the electrospun nanofiber precursor.By constructing such a heterostructured interface,the as-prepared sample delivers a high capacity of 160.3 mAh·g–1 at 1 C after 200 cycles,125.5 mAh·g–1 at 10 C after 500 cycles and a superior capacity retention of 90.3%after 1,000 cycles at 30 C,outperforming the heterostructure-free counterparts of pure LTO,RT and the commercial LTO product.Density Functional Theory calculation suggests a possible synergistic effect of the LTO/RT interface that would improve the electronic conductivity and Li-ion diffusion.
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(No.21972129)the Ministry of Science and Technology of China(2016YFA0200603)Anhui Initiative in Quantum Information Technologies(AHY090000)。
文摘In view of the high activity of Pt single atoms in the low-temperature oxidation of CO,we investigate the adsorption behavior of Pt single atoms on reduced rutile TiO2(110)surface and their interaction with CO and O2 molecules using scanning tunneling microscopy and density function theory calculations.Pt single atoms were prepared on the TiO2(110)surface at 80 K,showing their preferred adsorption sites at the oxygen vacancies.We characterized the adsorption configurations of CO and O2 molecules separately to the TiO2-supported Pt single atom samples at 80 K.It is found that the Pt single atoms tend to capture one CO to form Pt-CO complexes,with the CO molecule bonding to the fivefold coordinated Ti(Ti5 c)atom at the next nearest neighbor site.After annealing the sample from 80 K to 100 K,CO molecules may diffuse,forming another type of complexes,Pt-(CO)2.For O2 adsorption,each Pt single atom may also capture one O2 molecule,forming Pt-O2 complexes with O2 molecule bonding to either the nearest or the next nearest neighboring Ti5c sites.Our study provides the single-molecule-level knowledge of the interaction of CO and O2 with Pt single atoms,which represent the important initial states of the reaction between CO and O2.
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.
基金Project(2002AA327140) supported by National High-Tech Research and Development Program of China
文摘TiO2/Nb2O5 photocatalyst loaded with WO3 （WO3-TiO2/Nb2O5） was prepared by a modified hydrolysis process, and characterized by X-ray diffractometry, transmission electron microscopy, Raman spectra and UV-Vis diffuse refraction spectroscopy. The photocatalytic activity of WO3-TiO2/Nb2O5 was investigated by employing splitting of water for O2 evolution. The results indicate that WO3 loading can pronouncedly improve the photocatalytic activity of TiOjNb2O5 by using Fe^3＋ as an electron acceptor under UV irradiation. The optimum molar fraction of the loaded WO3 is 2%, and the largest speed of O2 evolution for 2% WO3-TiO2/Nb2O5 catalyst is 151.8 μmol/（L·h）.
基金Supported by the Natural Science Foundation of Fujian Province(No.2013J05027)Fujian Province Education-Science Project for Middle-aged and Young Teachers(No.JA13050)
文摘We report the synthesis of TiO2/ZnSn（OH）6 as a novel nano-composite material via a simultaneous crystallization-etching route with cubic nano-ZnSn（OH）6 and TiF4 as the precursors. The structure, composition and morphology of the composite were characterized by XRD, EDS, FETEM and FESEM, which showed the prepared TiO2/ZnSn（OH）6 had a unique morphology of hollow cubic nano-ZnSn（OH）6 attached with rutile TiO2 nanoparticles. The results of photocatalytic activity measurement indicated the photocatalytic activity of the prepared composite was better than that of nano-ZnSn（OH）6. This study may be helpful for the design and fabrication of functional comoosite materials.
基金financial support from the National Natural Science Foundation of China (Nos. 21421004, 21573067, 91545103)Program of Shanghai Academic Research Leader (No. 17XD1401400)
文摘Titanium dioxide（TiO2） is one of the most widely studied transition metal oxides, especially for its unique performances in heterogeneous photocatalysis. Different phases of TiO2 have been found to exhibit different photo-activities, though the origins are still not fully understood. In this work, we use the density functional theory（DFT） calculations, corrected by on-site Coulomb and long-range dispersion interactions, to study the adsorptions of nitric oxide（NO） and oxygen（O2） molecules on the clean and hydrogenated anatase TiO2（101） surfaces. We also compare the detailed calculated results regarding their structural, energetic and electronic properties with those obtained at rutile TiO2（110）. It has been found that the behaviors of the surface localized electrons being transferred from adsorbed H, as well as the adsorption behaviors of NO and O2 are quite different at the two surfaces, which can be attributed to their characteristic local bonding structures around the surface hydroxyl. These results may also help explain the different photocatalytic activities of these two main facets of anatase and rutile TiO2
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51472071 and 51272061)Talent Project of Hefei University of Technology,China(Grant Nos.75010-037004 and 75010-037003)
文摘The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 btm 2 in areal density were prepared by the hydrothermal method to replace the typical 200-300 nm thick mesoporous TiO2 thin films in perovskite solar cells. The CH3NH3PbI3 xBrx capping layers with different thicknesses were obtained on the TiO2 nanorod arrays using different concentration PbI2.DMSO complex precursor solutions in DMF and the photovoltaic performances of the corresponding solar cells were compared. The perovskite solar cells based on 240 nm long TiO2 nanorod arrays and 420 nm thick CH3NH3PbI3 xBrx capping layers showed the best photoelectric conversion efficiency （PCE） of 15.56% and the average PCE of 14.93 ± 0.63% at the relative humidity of 50%-54% under the illumination of simulated AM 1.5 sunlight （100 mW.cm-2）.
基金supported by the Key Program Projects of the National Natural Science Foundation of China (21631004)the National Natural Science Foundation of China (51672073)
文摘Oxygen vacancy（VO） plays a vital role in semiconductor photocatalysis. Rutile TiO2 nanomaterials with controllable contents of VO（0–2.18%） are fabricated via an insitu solid-state chemical reduction strategy, with color from white to black. The bandgap of the resultant rutile TiO2 is reduced from 3.0 to 2.56 e V, indicating the enhanced visible light absorption. The resultant rutile TiO2 with optimal contents of VO（2.07%） exhibits a high solar-driven photocatalytic hydrogen production rate of 734 μmol h-1, which is about four times as high as that of the pristine one（185 μmol h-1）. The presence of VOelevates the apparent Fermi level of rutile TiO2 and promotes the efficient electronhole separation obviously, which favor the escape of photogenerated electrons and prolong the life-time（7.6×103 ns） of photogenerated charge carriers, confirmed by scanning Kelvin probe microscopy, surface photovoltage spectroscopy and transient-state fluorescence. VO-mediated efficient photogenerated electron-hole separation strategy may provide new insight for fabricating other high-performance semiconductor oxide photocatalysts.
基金Project supported in part by the Major Program of National Science Foundation of China(No.51090385)the National Natural Science Foundation of China(No.50974067)
文摘Traditionally, we use a slab to mimic a surface and we constrain the slab to have the bulk-terminated 2D lattice constants. Here we propose a different model in which we impose no constraints, allowing all coordinates including the 2D slab itself to relax. We perform DFT calculations on both models. We find that the unconstrained slabs yield better agreement with experimental results and they have lower total energies. The optimized 2D lattice constants of the unconstrained slabs eventually converge to the attached bulk value. The total energy difference reveals that, with odd number trilayers, the unconstrained slab is much closer to the corresponding constrained slab. The surface energies both converge to the individual values with the number of atomic layers.
基金The authors are grateful for a research grant from Shanghai Education Committee (07ZZ180)a fund from the Second Shanghai Key Discipline Construction Plan of Shanghai Municipal EducationCommission (P1701)
文摘Photodegradation of benzene at ppb levels by mixed-phase TiO2 nanoparticles, synthesized by the oxidation of TiCl4 in propane/air turbulent flame chemical vapor deposition （CVD） process, is investigated experimentally by using a tubular photoreactor with thin TiO2 films coated on the reactor wall by sedimentation. Effects of inlet benzene concentration from 10 to 300μg/m3, rutile mass fraction from about 20 to 50% and photoluminescence （PL） intensity of TiO2 nanoparticles on degradation degree are examined under the conditions of 70% relative humidity, 38 μg/cm2 catalyst loading, 24mW/cm2 UV irradiation of 254 nm and 5.7 s residence time in the reactor. Based on experimental results, separation of photoinduced electron （e-） and hole （h＋） pairs by rutile phase is discussed as photo-induced electron （e-） in anatase phase will migrate to rutile surface due to that the potential of conductive band of rutile is lower than that of anatase, leading to more holes ready on anatase surface for oxidation reactions.
