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1.
A mixed oxide consisting of TiO2 as the major phase and CeO2−y (0<y<0.5) as the dopant phase was prepared via the sol-gel reaction of Ti(i-OC3H7)3 in an aqueous solution of Ce(NO3)3. The resulting oxide powders with different CeO2−y contents were all composed of nano-sized spheres. The CeO2−y phase was identified to have retarding effect on the phase transition from anatase TiO2 to rutile TiO2 at calcinations temperature as high as 800 °C, which would otherwise be a thorough conversion. The CeO2−y-TiO2 powders could apparently shift the UV-absorption band of TiO2 toward visible range, and there was an optimal CeO2−y content in association with the maximum absorbance. This effect is interpreted as the existence of an n-type impurity band, due to the substitution of Ti4+ for Ce3+/4+ at the interface between the two oxides, in the gap of TiO2. According to X-ray photoelectron spectroscopy (XPS) investigation, the Ti element mainly existed as the chemical state of Ti4+ and the Ce oxide doping did not affect the peak position of Ti 2p. The Ce 3d spectrum of CeO2−y-doped TiO2 sample basically denotes a mixture of Ce3+/4+ oxidation states giving rise to a myriad of peaks.  相似文献   

2.
No-noble metal CeO2-TiO2 catalysts prepared by sol-gel method were developed and examined for catalytic wet air oxidation (CWAO) of acetic acid. The structure of the catalysts was measured by BET, SEM, XRD, XPS and DTA-TG. We investigated the effect of the interactions of Ce and Ti on the structure of CeO2-TiO2 catalysts. The mechanisms of the relationships between the different content of Ti and the activity of CeO2-TiO2 catalysts were discussed. The results showed that the average crystal size of CeO2 decreased and the surface areas increased; the low valence of Ce3+ increase, and the chemisorbed oxygen slightly decreased with the increase of Ti content on the surface of CeO2-TiO2 catalysts. The order of the activity in CWAO of acetic acid followed: Ce/Ti 1/1 > Ce/Ti 3/1 > Ce/Ti 1/3 > Ce/Ti 5/1 > CeO2 > TiO2 > no catalyst. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO2-TiO2 catalysts was observed in our study.  相似文献   

3.
Pure and Ce4+ doped anatase and rutile TiO2 were prepared by hydrothermal methods and characterized by XRD, TEM, UV-vis diffusion spectroscopy, and XPS measurements. The photocatalytic reactivity of the catalysts was evaluated by the photodegradation of Rhodamine B (RB) under ultraviolet irradiation. The photocatalytic efficiency of the rutile sample doped with an appropriate amount of Ce4+ was enhanced while all Ce4+ doped anatase samples showed a much lower activity than pure anatase. The reasons were discussed  相似文献   

4.
In this study we present the effects of iron oxide (Fe2O3) on titanium dioxide (TiO2) in synthesising visible-light reactive photocatalysts. A Fe2O3-TiO2 composite photocatalyst was synthesized from Fe2(SO4)3 and Ti(SO4)2 by a ethanol-assisted hydrothermal method. The preparation conditions were optimized through the investigation of the effects of hydrothermal temperature and time as well as molar ratio of Ti to Fe on the photocatalytic activity. The visual, physical and chemical properties of the Fe2O3-TiO2 composites were investigated. The results showed that α-Fe2O3 and anatase TiO2 were present in the composites. The Fe2O3-TiO2 synthesized under optimum condition consisted of mesoporous structure with an average pore size of 4 nm and a surface area of 43 m2/g. Under visible and solar light irradiation, the photocatalytic activity of optimized sample was significantly higher than that of pure TiO2. This sample led to a photodegradation efficiency of 90% and 40% of auramine under visible light and solar light, respectively.  相似文献   

5.
There are two major difficulties in the TiO2 liquid-solid photocatalytic system: effective immobilization of the TiO2 particles; and improving the catalytic activity under visible light. To simultaneously solve these two problems, Fe2O3-TiO2 coatings supported on activated carbon fiber (ACF), have been prepared in one step by a convenient and efficient method—metal organic chemical vapor deposition (MOCVD). XRD results revealed that Fe2O3-TiO2 coatings mainly composed of anatase TiO2, α-Fe2O3 phases and little Fe2Ti3O9. The pore structure of ACF was preserved well after loading with Fe2O3-TiO2 coatings. UV-vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an enhancement of the absorption in the visible region for Fe2O3-TiO2 coatings, compared to the pure TiO2 sample. A moderate Fe2O3-TiO2 loading (13.7 wt%) was beneficial to mineralizing wastewater because the intermediates could be adsorbed onto the surface of photocatalyst following decomposition. The stable performance revealed that the Fe2O3-TiO2 coatings were strongly adhered to the ACF surface, and the as prepared catalysts could be reused showing potential application for wastewater treatment.  相似文献   

6.
The effect of low pressure radio frequency (rf) plasma treatment on TiO2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti3+ 2p3/2 state after plasma treatment with a very good stability, whereas untreated TiO2 remained mostly as Ti4+ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO2 surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO2 has advantages to surface carbon cleaning, increasing O and Ti3+ surface states, hence improving the activity of TiO2 for different environmental, energy and biological applications.  相似文献   

7.
Eu3+掺杂的Sr2CeO4发光材料的光致发光研究   总被引:1,自引:0,他引:1       下载免费PDF全文
符史流  尹涛  丁球科  赵韦人 《物理学报》2006,55(9):4940-4945
利用高温固相反应法制备了Eu3+掺杂的Sr2CeO4样品,并对其吸附水前后的光谱特性进行了研究.结果发现,对于刚制备的Sr2-xEuxCeO4+x/2样品, 在Ce4+—O2-的电荷迁移激发中,只有强激发带(~35700cm-1)与Eu3+离子间存在能量传递,而弱激发带 (~29400cm-1)只是引起Ce4+—O2-的电荷迁移发射;在Sr2-xEuxCeO4+x/2样品吸附水后,Eu3+的线状吸收跃迁强度显著增加, Ce4+—O2-两个激发带均向Eu3+离子传递能量. Ce4+—O2-强激发带通过交换作用向Eu3+离子传递能量,而弱激发带与Eu3+离子间的能量传递机理是非辐射多极子近场力的相互作用. 关键词: 2-xEuxCeO4+x/2')" href="#">Sr2-xEuxCeO4+x/2 发光性质 能量传递 吸附水  相似文献   

8.
The interaction of Pt with CeO2 layers was investigated by using high resolution hard X-ray photoelectron spectroscopy. Pt doped CeO2 layers were deposited simultaneously by rf-magnetron sputtering on a SiO2/Si substrate and carbon nanotubes (CNTs) grown on a carbon diffusion layer of a polymer membrane fuel cell. In the case of the CNT support photoelectron spectra showed the formation of ionic platinum rich cerium oxide with Pt2+,4+ species, and with the Pt2+/Pt4+ ratio strongly dependent on the amount of platinum. Ce reveals 4+/3+ mixed valent character with Ce3+ concentration increasing with Pt content. In the case of the SiO2/Si substrate the film revealed Ce4+ and Pt4+ species only.  相似文献   

9.
Mixed phase TiO2 and Ce/TiO2 samples were synthesized by a sol–gel method using different hydrolysis conditions. In pure TiO2 samples, traditional X-ray diffraction (XRD) and Ti K-edge synchrotron X-ray absorption near edge structures (XANES) independently revealed their anatase/rutile phase ratios. XANES results further revealed a substantial amount of Ti atoms existed in other forms beside anatase and rutile TiO2 in the sample synthesized by the low hydrolysis condition. An increase in the extent of the hydrolysis during the synthesis leads to an increased rutile ratio and a reduction in other forms. In Ce/TiO2 samples, the crystal sizes were too small for XRD characterization. Only XANES could be used to characterize their phase ratios. It is found that adding Ce impedes rutile formation; leading to increased anatase ratio. The difference in the fundamental aspects of XRD and XANES techniques in providing the phase ratios is discussed.  相似文献   

10.
A series of Ce-TiO2 are prepared by the sol-gel process with ammonium cerium(IV) nitrate and tetra-n-butyl titanium as raw materials and characterized with XRD, TEM, DRS, and XPS. The aberrance (0.355) of anatase(1 0 1) plane of 0.1% Ce/TiO2 increases compared to that of TiO2. Cerium is found to be present as a mixture of Ce3+/4+ oxidation states, that is, the oxidation state of some cerium in Ce-TiO2 has changed after calcination. Ce/TiO2 yields a large red shift compared to TiO2. Moreover, the reflectance decreases in the visible region after cerium doped on TiO2, and the lower the reflectance the higher the activity. Cerium appears to enhance the photocatalytic activity of Ce/TiO2 by suppressing electron-hole recombination with electron trapping at Ce4+. 0.1% Ce/TiO2 shows highest activity for the degradation of aqueous suspension of formaldehyde.  相似文献   

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