Ultrathin TiO_(2)nanosheets with coexposed{001}/{101}facets have attracted considerable attention because of their high photocatalytic activity.However,the charge-separated states in the TiO_(2)nanosheets must be exte...Ultrathin TiO_(2)nanosheets with coexposed{001}/{101}facets have attracted considerable attention because of their high photocatalytic activity.However,the charge-separated states in the TiO_(2)nanosheets must be extended to further enhance their photocatalytic activity for H_(2)evolution.Herein,we present a successful attempt to selectively dope lanthanide ions into the{101}facets of ultrathin TiO_(2)nanosheets with coexposed{001}/{101}facets through a facile one-step solvothermal method.The lanthanide doping slightly extended the light-harvesting region and markedly improved the charge-separated states of the TiO_(2)nanosheets as evidenced by UV-vis absorption and steady-state/transient photoluminescence spectra.Upon simulated sunlight irradiation,we observed a 4.2-fold enhancement in the photocatalytic H_(2)evolution activity of optimal Yb^(3+)-doped TiO_(2)nanosheets compared to that of their undoped counterparts.Furthermore,when Pt nanoparticles were used as cocatalysts to reduce the H_(2)overpotential in this system,the photocatalytic activity enhancement factor increased to 8.5.By combining these results with those of control experiments,we confirmed that the extended charge-separated states play the main role in the enhancement of the photocatalytic H_(2)evolution activity of lanthanide-doped TiO_(2)nanosheets with coexposed{001}/{101}facets.展开更多
{001}facets dominated single crystalline anatase TiO_(2) nanosheet array(TNSA)was synthe-sized through an optimized organic solvothermal route on uorine-doped tin oxide substrate.The field emission scanning electron m...{001}facets dominated single crystalline anatase TiO_(2) nanosheet array(TNSA)was synthe-sized through an optimized organic solvothermal route on uorine-doped tin oxide substrate.The field emission scanning electron microscopy images and X-ray diffraction patterns re-vealed that the{001}synthesized facets dominated TNSA exhibited much higher orientation than that synthesized by hydrothermal route.The TNSAs were loaded with Pt nanoparti-cles in uniformly size by using a photodecomposition method,which were further con rmed by high resolution transmission electron microscopy(HRTEM).The HRTEM images also revealed that Pt nanoparticles preferred to deposit on{001}facets.With loading of Pt nanoparticles,the optical absorbance was significantly enhanced,while the photolumines-cence(PL)was inhibited.The photocatalytic activity of TNSA was signi cantly improved by Pt loading and reached the maximum with optimal amount of Pt loading.The optimal amount of Pt on{001}facets is far less than that on TiO_(2) nanoparticles,which may be attributed to the specific atom structure of reactive{001}facets.展开更多
Tailored synthesis of well-defined anatase TiO_(2)-based crystals with exposed{001}facets has stimulated incessant research interest worldwide due to their scientific and technological importance.Herein,anatase nitrog...Tailored synthesis of well-defined anatase TiO_(2)-based crystals with exposed{001}facets has stimulated incessant research interest worldwide due to their scientific and technological importance.Herein,anatase nitrogen-doped TiO_(2)(N-TiO_(2))nanoparticles with exposed{001}facets deposited on the graphene(GR)sheets(N-TiO_(2)-001/GR)were synthesized for the first time via a one-step solvothermal synthetic route using NH4F as the morphology-controlling agent.The experimental results exemplified that GR was uniformly covered with anatase N-TiO_(2) nanoparticles(10-17 nm),exposing the{001}facets.The percentage of exposed{001}facets in the N-TiO_(2)-001/GR nanocomposites was calculated to be ca.35%.Also,a red shift in the absorption edge and a strong absorption in the visible light range were observed due to the formation of Ti-O-C bonds,resulting in the successful narrowing of the band gap from 3.23 to 2.9 eV.The photocatalytic activities of the as-prepared photocatalysts were evaluated for CO_(2) reduction to produce CH,in the presence of water vapor under ambient temperature and atmospheric pressure using a low-power 15 W energy-saving daylight lamp as the visible light source--in contrast to the most commonly employed high-power xenon lamps--which rendered the process economically and practically feasible.Among all the studied photocatalysts,the N-TiO_(2)-001/GR nanocomposites exhibited the greatest CH4 yield of 3.70 p-mol'gcatalyst 1,approxi-mately 11-fold higher activity than the TiO_(2)-001.The enhancement of photocatalyfic performance was ascribed to the effective charge anti-recombination of graphene,high absorption of visible light region relative to the{101}facets.and high catalytic activity of{001}facets.展开更多
文摘Ultrathin TiO_(2)nanosheets with coexposed{001}/{101}facets have attracted considerable attention because of their high photocatalytic activity.However,the charge-separated states in the TiO_(2)nanosheets must be extended to further enhance their photocatalytic activity for H_(2)evolution.Herein,we present a successful attempt to selectively dope lanthanide ions into the{101}facets of ultrathin TiO_(2)nanosheets with coexposed{001}/{101}facets through a facile one-step solvothermal method.The lanthanide doping slightly extended the light-harvesting region and markedly improved the charge-separated states of the TiO_(2)nanosheets as evidenced by UV-vis absorption and steady-state/transient photoluminescence spectra.Upon simulated sunlight irradiation,we observed a 4.2-fold enhancement in the photocatalytic H_(2)evolution activity of optimal Yb^(3+)-doped TiO_(2)nanosheets compared to that of their undoped counterparts.Furthermore,when Pt nanoparticles were used as cocatalysts to reduce the H_(2)overpotential in this system,the photocatalytic activity enhancement factor increased to 8.5.By combining these results with those of control experiments,we confirmed that the extended charge-separated states play the main role in the enhancement of the photocatalytic H_(2)evolution activity of lanthanide-doped TiO_(2)nanosheets with coexposed{001}/{101}facets.
基金This work is supported by the National Basic Research Program of China(No.2012CB9222000).
文摘{001}facets dominated single crystalline anatase TiO_(2) nanosheet array(TNSA)was synthe-sized through an optimized organic solvothermal route on uorine-doped tin oxide substrate.The field emission scanning electron microscopy images and X-ray diffraction patterns re-vealed that the{001}synthesized facets dominated TNSA exhibited much higher orientation than that synthesized by hydrothermal route.The TNSAs were loaded with Pt nanoparti-cles in uniformly size by using a photodecomposition method,which were further con rmed by high resolution transmission electron microscopy(HRTEM).The HRTEM images also revealed that Pt nanoparticles preferred to deposit on{001}facets.With loading of Pt nanoparticles,the optical absorbance was significantly enhanced,while the photolumines-cence(PL)was inhibited.The photocatalytic activity of TNSA was signi cantly improved by Pt loading and reached the maximum with optimal amount of Pt loading.The optimal amount of Pt on{001}facets is far less than that on TiO_(2) nanoparticles,which may be attributed to the specific atom structure of reactive{001}facets.
文摘Tailored synthesis of well-defined anatase TiO_(2)-based crystals with exposed{001}facets has stimulated incessant research interest worldwide due to their scientific and technological importance.Herein,anatase nitrogen-doped TiO_(2)(N-TiO_(2))nanoparticles with exposed{001}facets deposited on the graphene(GR)sheets(N-TiO_(2)-001/GR)were synthesized for the first time via a one-step solvothermal synthetic route using NH4F as the morphology-controlling agent.The experimental results exemplified that GR was uniformly covered with anatase N-TiO_(2) nanoparticles(10-17 nm),exposing the{001}facets.The percentage of exposed{001}facets in the N-TiO_(2)-001/GR nanocomposites was calculated to be ca.35%.Also,a red shift in the absorption edge and a strong absorption in the visible light range were observed due to the formation of Ti-O-C bonds,resulting in the successful narrowing of the band gap from 3.23 to 2.9 eV.The photocatalytic activities of the as-prepared photocatalysts were evaluated for CO_(2) reduction to produce CH,in the presence of water vapor under ambient temperature and atmospheric pressure using a low-power 15 W energy-saving daylight lamp as the visible light source--in contrast to the most commonly employed high-power xenon lamps--which rendered the process economically and practically feasible.Among all the studied photocatalysts,the N-TiO_(2)-001/GR nanocomposites exhibited the greatest CH4 yield of 3.70 p-mol'gcatalyst 1,approxi-mately 11-fold higher activity than the TiO_(2)-001.The enhancement of photocatalyfic performance was ascribed to the effective charge anti-recombination of graphene,high absorption of visible light region relative to the{101}facets.and high catalytic activity of{001}facets.
