The energetic pathways of adsorption and activation of carbon dioxide (CO2) on low-lying compact (TiO2)n clusters are systematically investigated by using electronic structure calculations based on density-functional ...The energetic pathways of adsorption and activation of carbon dioxide (CO2) on low-lying compact (TiO2)n clusters are systematically investigated by using electronic structure calculations based on density-functional theory (DFT). Our calculated results show that CO2 is adsorbed preferably on the bridge O atom of the clusters, forming a "chemisorption" carbonate complex, while the CO is adsorbed preferably to the Ti atom of terminal Ti-O.The computed carbonate vibrational frequency values are in good agreement with the results obtained experimentally, which suggests that CO2 in the complex is distorted slightly from its undeviating linear configuration. In addition, the analyses of electronic parameters, electronic density, ionization potential, HOMO-LUMO gap, and density of states(DOS) confirm the charge transfer and interaction between CO2 and the cluster. From the predicted energy profiles, CO2 can be easily adsorbed and activated, while the activation of CO2 on (TiO2)n clusters are structure-dependent and energetically more favorable than that on the bulk TiO2. Overall, this study critically highlights how the small (TiO2)n clusters can influence the CO2 adsorption and activation which are the critical steps for CO2 reduction the surface of a catalyst and subsequent conversion into industrially relevant chemicals and fuels.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
Using ZnSO4 and TiCl4 as raw materials, nanometric TiO2 ZnO (ZnTiO3) is prepared at 180℃,0.8MPa by hydrothermal method. The effects of the reaction temperature and time on the nanometric TiO2 ZnO are also discussed. ...Using ZnSO4 and TiCl4 as raw materials, nanometric TiO2 ZnO (ZnTiO3) is prepared at 180℃,0.8MPa by hydrothermal method. The effects of the reaction temperature and time on the nanometric TiO2 ZnO are also discussed. XRD shows that the product is TiO2 ZnO (ZnTiO3) with noncrystal phase, and it changes to rhombic form above 870℃. TEM measurement indicates that the TiO2 ZnO is spherical particles, and the average diameter of the particles is 20nm. The UV light absorption properties are detected by UV spectrophotometer. The results show that the nanometric TiO2 ZnO has strong absorption at 200～370nm and at visible region. Photodegradation of dyes in an aqueous solution is investigated using nanometric TiO2 ZnO as a photocatalyst. The results show that after 60min illumination, the decolorization rate of the acidic red B and acidic black 234 dye can be arrived at 100%.展开更多
基金partially supported by the National Natural Science Foundation of China(No.11404074)
文摘The energetic pathways of adsorption and activation of carbon dioxide (CO2) on low-lying compact (TiO2)n clusters are systematically investigated by using electronic structure calculations based on density-functional theory (DFT). Our calculated results show that CO2 is adsorbed preferably on the bridge O atom of the clusters, forming a "chemisorption" carbonate complex, while the CO is adsorbed preferably to the Ti atom of terminal Ti-O.The computed carbonate vibrational frequency values are in good agreement with the results obtained experimentally, which suggests that CO2 in the complex is distorted slightly from its undeviating linear configuration. In addition, the analyses of electronic parameters, electronic density, ionization potential, HOMO-LUMO gap, and density of states(DOS) confirm the charge transfer and interaction between CO2 and the cluster. From the predicted energy profiles, CO2 can be easily adsorbed and activated, while the activation of CO2 on (TiO2)n clusters are structure-dependent and energetically more favorable than that on the bulk TiO2. Overall, this study critically highlights how the small (TiO2)n clusters can influence the CO2 adsorption and activation which are the critical steps for CO2 reduction the surface of a catalyst and subsequent conversion into industrially relevant chemicals and fuels.
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.
文摘Using ZnSO4 and TiCl4 as raw materials, nanometric TiO2 ZnO (ZnTiO3) is prepared at 180℃,0.8MPa by hydrothermal method. The effects of the reaction temperature and time on the nanometric TiO2 ZnO are also discussed. XRD shows that the product is TiO2 ZnO (ZnTiO3) with noncrystal phase, and it changes to rhombic form above 870℃. TEM measurement indicates that the TiO2 ZnO is spherical particles, and the average diameter of the particles is 20nm. The UV light absorption properties are detected by UV spectrophotometer. The results show that the nanometric TiO2 ZnO has strong absorption at 200～370nm and at visible region. Photodegradation of dyes in an aqueous solution is investigated using nanometric TiO2 ZnO as a photocatalyst. The results show that after 60min illumination, the decolorization rate of the acidic red B and acidic black 234 dye can be arrived at 100%.
