IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and character...IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and characterized by means of structural,surface analytical and electrochemical techniques.Nb doping of titania significantly increased the surface area of the support from 145(TNTs)to 260 m2g-1(Nb-TNTs),which was significantly higher than those of the Nb-doped titania supports previously reported in the literature.The surface analytical techniques showed good dispersion of the catalysts onto the supports.The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV)species,the suitable form to behave as a donor introducing free electrons to the conduction band of titania.The redox transitions of the cyclic voltammograms,in agreement with the XPS results,were found to be reversible.Despite the supported materials presented bigger crystallite sizes than the unsupported ones,the total number of active sites of the former was also higher due to their better catalyst dispersion.Considering the outer and the total charges of the cyclic voltammograms in the range 0.1–1.4 V,stability and electrode potentials at given current densities,the preferred catalyst was Ir O2 supported on the Nb-TNTs.The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping,thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER.The good dispersion of IrO2,high specific surface area of the Nb-doped supports,accessibility of the electroactive centers,increased stability due to Nb doping and electron donor properties of the Nb(IV)oxide species were considered the main reasons for its good performance.展开更多
Nb-doped TiO2 nanoparticles were prepared by hydrothermal treatment of titanate nanotubes in niobium oxalate aqueous solution.The effect of Nb doping and rutile content on the photoelectrochemical performance based on...Nb-doped TiO2 nanoparticles were prepared by hydrothermal treatment of titanate nanotubes in niobium oxalate aqueous solution.The effect of Nb doping and rutile content on the photoelectrochemical performance based on TiO2 powder electrodes was investigated.The results show that Nb-doped TiO2 with a small amount of rutile exhibits the enhanced photoelectric conversion efficiency for dye-sensitized solar cell.The highest photoelectric conversion efficiency of 8.53%is obtained for 1%Nb—TiO2 containing a small amount of rutile.When a small amount of rutile contained in 2%Nb—TiO2,a higher photoelectric conversion efficiency of8.77%is achieved.展开更多
Nb and F co-doped anatase TiO2 layers were deposited by low pressure chemical vapor deposition (LPCVD) at pressure of 3 mtorr using titanium-tetra-iso-propoxide (TTIP), O2 and NbF5 as precursor, oxidant and dopant res...Nb and F co-doped anatase TiO2 layers were deposited by low pressure chemical vapor deposition (LPCVD) at pressure of 3 mtorr using titanium-tetra-iso-propoxide (TTIP), O2 and NbF5 as precursor, oxidant and dopant respectively. Resistivity beyond 100 Ωcm for undoped layer was decreased with increasing supply of the dopant and dependent on the supply ratio of O2 to TTIP and decreased to 0.2 Ωcm by the optimization. X-ray fluorescent spectroscopy showed Nb-content in the layer was decreased with the O2-supply ratio. X-ray photo-spectroscopy indicated that F substituted O-site in TiO2 by O2-supply but carbon-contamination and F missing substitution in the O-site were significantly increased by excess O2-supply. Further, it was suggested that the substituted F played an important role to reduce resistivity without significant contribution of O-vacancies. XRD spectra showed F missing substitution in the O-site degraded the crystallinity.展开更多
Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and NbF5 in H2-ambient. Acti-vation energy for the depositi...Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and NbF5 in H2-ambient. Acti-vation energy for the deposition rate on the temperature was significantly decreased to 120 kJ/mol as compared with 228 kJ/mol for the deposition in H2 without NbF5. The deposition rate linearly increased with NbF5 supply rate but gradually decreased with H2 supply rate indicated that F on the deposition surface acts as catalyst for TTIP-dissociation but is non-activated by hydrogen. Resistivity of the layer was decreased by NbF5 supply depending on the deposition temperature with the activation energy of 319 kJ/mol, whereas the energy was 244 kJ/mol for the layer deposited in H2 without NbF5. The dependence of resistivity on NbF5. and H2 supply rates suggested that the doping should be performed by sufficient NbF5 and H2 supply rate to improve the crystallinity. As a result of the optimization, the resistivity was successfully reduced to 5 × 10-2 Ω·cm. Optical transmission spectra in UV-Vis region indicated that significant absorption observed for the layer deposited in H2 was notably decreased by using NbF5. The improved optical property was better than that for the layer deposited in O2-ambient.展开更多
基金Scientific Research Foundation of the Educational Commission of Heilongjiang Province of China(472014)Application Technology Research and Development Projects of Heilongjiang Province(2013G0529)
文摘IrO2 and IrRuOx(Ir:Ru 60:40 at%),supported by 50 wt%onto titania nanotubes(TNTs)and(3 at%Nb)Nb-doped titania nanotubes(Nb-TNTs),as electrocatalysts for the oxygen evolution reaction(OER),were synthesized and characterized by means of structural,surface analytical and electrochemical techniques.Nb doping of titania significantly increased the surface area of the support from 145(TNTs)to 260 m2g-1(Nb-TNTs),which was significantly higher than those of the Nb-doped titania supports previously reported in the literature.The surface analytical techniques showed good dispersion of the catalysts onto the supports.The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV)species,the suitable form to behave as a donor introducing free electrons to the conduction band of titania.The redox transitions of the cyclic voltammograms,in agreement with the XPS results,were found to be reversible.Despite the supported materials presented bigger crystallite sizes than the unsupported ones,the total number of active sites of the former was also higher due to their better catalyst dispersion.Considering the outer and the total charges of the cyclic voltammograms in the range 0.1–1.4 V,stability and electrode potentials at given current densities,the preferred catalyst was Ir O2 supported on the Nb-TNTs.The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping,thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER.The good dispersion of IrO2,high specific surface area of the Nb-doped supports,accessibility of the electroactive centers,increased stability due to Nb doping and electron donor properties of the Nb(IV)oxide species were considered the main reasons for its good performance.
基金supported by the National Natural Science Foundation of China(No.51172233)the Major State Basic Research Development Program of China("973 Program",No. 2009CB220002)the Key Laboratory of Water and Air Pollution Control of Guandong Province,China(GD2012A05)
文摘Nb-doped TiO2 nanoparticles were prepared by hydrothermal treatment of titanate nanotubes in niobium oxalate aqueous solution.The effect of Nb doping and rutile content on the photoelectrochemical performance based on TiO2 powder electrodes was investigated.The results show that Nb-doped TiO2 with a small amount of rutile exhibits the enhanced photoelectric conversion efficiency for dye-sensitized solar cell.The highest photoelectric conversion efficiency of 8.53%is obtained for 1%Nb—TiO2 containing a small amount of rutile.When a small amount of rutile contained in 2%Nb—TiO2,a higher photoelectric conversion efficiency of8.77%is achieved.
文摘Nb and F co-doped anatase TiO2 layers were deposited by low pressure chemical vapor deposition (LPCVD) at pressure of 3 mtorr using titanium-tetra-iso-propoxide (TTIP), O2 and NbF5 as precursor, oxidant and dopant respectively. Resistivity beyond 100 Ωcm for undoped layer was decreased with increasing supply of the dopant and dependent on the supply ratio of O2 to TTIP and decreased to 0.2 Ωcm by the optimization. X-ray fluorescent spectroscopy showed Nb-content in the layer was decreased with the O2-supply ratio. X-ray photo-spectroscopy indicated that F substituted O-site in TiO2 by O2-supply but carbon-contamination and F missing substitution in the O-site were significantly increased by excess O2-supply. Further, it was suggested that the substituted F played an important role to reduce resistivity without significant contribution of O-vacancies. XRD spectra showed F missing substitution in the O-site degraded the crystallinity.
文摘Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and NbF5 in H2-ambient. Acti-vation energy for the deposition rate on the temperature was significantly decreased to 120 kJ/mol as compared with 228 kJ/mol for the deposition in H2 without NbF5. The deposition rate linearly increased with NbF5 supply rate but gradually decreased with H2 supply rate indicated that F on the deposition surface acts as catalyst for TTIP-dissociation but is non-activated by hydrogen. Resistivity of the layer was decreased by NbF5 supply depending on the deposition temperature with the activation energy of 319 kJ/mol, whereas the energy was 244 kJ/mol for the layer deposited in H2 without NbF5. The dependence of resistivity on NbF5. and H2 supply rates suggested that the doping should be performed by sufficient NbF5 and H2 supply rate to improve the crystallinity. As a result of the optimization, the resistivity was successfully reduced to 5 × 10-2 Ω·cm. Optical transmission spectra in UV-Vis region indicated that significant absorption observed for the layer deposited in H2 was notably decreased by using NbF5. The improved optical property was better than that for the layer deposited in O2-ambient.
