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1.
Au/TiO2 catalysts prepared by photo-deposition method for selective CO oxidation in H2 stream 总被引:1,自引:0,他引:1
Yi-Fen Yang Palanivelu Sangeetha Yu-Wen Chen 《International Journal of Hydrogen Energy》2009,34(21):8912-8920
A series of Au/TiO2 catalysts were prepared by photo-deposition (PD) method. Various preparation parameters, such as pH value, power of UV light and irradiation time on the characteristics of the catalysts were investigated. The catalysts were characterized by inductively-coupled plasma-mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The preferential oxidation of CO in H2 stream (PROX) on these catalysts was carried out in a fixed-bed micro reactor with a feed of CO: O2: H2: He = 1: 1: 49: 49 (volume ratios) and a space velocity of 30,000 ml/g h. Limited amount of O2 was used to investigate the selectivity of O2 reacting with CO or H2. Au/TiO2 catalysts prepared by PD method showed narrow particle size distribution of gold particles within few nanometers and were found to be 1.5 nm. The particle size of gold nanoparticles deposited on the support depends on irradiation time, UV light source and pH value of preparation. The electronic structure of Au was a function of particle size. The smaller the Au particle size was, the higher the concentration of Au cation was. Using weak power of UV light, appropriate irradiation time and suitable pH value, very fine gold particles on the support could be obtained even in the powder form. The samples prepared with PD method did not need heat treatment to reduce Au cation, UV irradiation could reduce it. Therefore it is easier to have smaller particle size. Au/TiO2 catalysts prepared by PD method were very active and selective in PROX reaction. In long time test, the catalysts were stable at 80 °C for more than 60 h. 相似文献
2.
The CeO2/CuO and CuO/CeO2 catalysts were synthesized by the hydrothermal method and characterized via XRD, SEM, H2-TPR, HRTEM, XPS and N2 adsorption–desorption techniques. The study shows that the rod-like structure is self-assembled CeO2, and both hydrothermal time and Ce/Cu molar ratio are important factors when the particle-like CeO2 is being self-assembled into the rod-like CeO2. The CuO is key active component in the CO-PROX reaction, and its reduction has a negative influence on the selective oxidation of CO. The advantage of the inverse CeO2/CuO catalyst is that it still can provide sufficient CuO for CO oxidation before 200 °C in the hydrogen-rich reductive gasses. The traditional CuO/CeO2 catalyst shows better activity at lower temperature and the inverse CeO2/CuO catalysts present higher CO2 selectivity when the CO conversion reaches 100%. The performance of mixed sample verifies that they might be complementary in the CO-PROX system. 相似文献
3.
Amita Verma S.B. Samanta N.C. Mehra A.K. Bakhshi S.A. Agnihotry 《Solar Energy Materials & Solar Cells》2005,86(1):85-103
Mixed CeO2–TiO2 coatings synthesized by sol–gel spin coating process using mixed organic–inorganic Ti(OC3H7)4 and CeCl3·7H2O precursors with different Ce/Ti mole ratios were investigated by a wide range of characterization techniques. The attempts were directed towards achieving coatings with high transparency in the visible region and good electrochemical properties. Elucidation of the structural and optical features of the films yielded information on the aspects relevant to their usage in transmissive electrochromic devices. The films have been found to exhibit properties for counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion, high enough for practical uses. The high optical modulation and fastest switching for WO3 film in the device configuration with the Ce/Ti (1:1) film is interpreted in terms of conducive microstructural changes induced by addition of TiO2 in an amount equivalent to CeO2. 相似文献
4.
Apanee Luengnaruemitchai Sahil Chawla Ratchaneekorn Wanchanthuek 《International Journal of Hydrogen Energy》2014
The Au/La-CeOx catalysts were prepared and tested for the PROX reaction. The effects of the support preparation method, Au loading, calcination temperature, oxygen pretreatment on the catalytic activity, and the stability test were investigated. It was found that the catalyst preparation could affect the surface area, gold particle size, and the state of gold, which are strongly related to the catalytic activity. The results indicated that the La-CeOx prepared by the NH4OH precipitation method have high activity and thermal stability. Under the stability test, the catalyst was stable, even though water was added in the feed stream up to 10%. 相似文献
5.
R. Prez-Hernndez A. Gutirrez-Martínez J. Palacios M. Vega-Hernndez V. Rodríguez-Lugo 《International Journal of Hydrogen Energy》2011,36(11):6601-6608
Single ZrO2 and mixed CeO2-ZrO2 oxides with different CeO2/ZrO2 ratios were prepared by the sol-gel method and the CeO2 by precipitation. The prepared support were impregnated with an aqueous solution of NiCl2·6H2O at an appropriate concentration to yield 3 wt.% of nickel respectively in the catalysts. Catalytic materials were characterized by BET (N2 adsorption-desorption), SEM-EDS, XRD and TPR. The oxidative steam reforming of methanol (OSRM) reaction was investigated on these catalysts for H2 production as a function of temperature. Depending of the CeO2/ZrO2 ratio; the catalysts composition has a significant influence on the surface area (BET), reduction properties and methanol conversion. XRD patterns of the Ni-base catalysts showed well defined diffraction peaks of the metallic Ni except on the Ni/CeO2 catalyst, suggesting that on this sample all of the active phase was highly dispersed. Ni/Ceria-rich catalysts were vastly active for OSRM, giving a total CH3OH conversion at 325 °C with GHSV = 0.3 × 105 h−1. They also showed close selectivity toward H2, with high selectivity to CO2 in all range of temperatures, this suggests that the reverse WGS reaction does not occur on these samples. It seems that the nickel is the phase mainly responsible of hydrogen production although the CeO2/ZrO2 support reduces the CO formation. 相似文献
6.
7.
Influence of crystallite size and interface on the catalytic performance over the CeO2/CuO catalysts
The solvothermal method was used to prepare the CuO precursor with cotton-ball-like morphology in order to obtain the CeO2/CuO catalysts with high BET surface area. The catalysts were characterized via SEM, XRD, H2-TPR, ICP, HRTEM and N2 adsorption–desorption techniques. The study shows that CeO2 and CuO interact on the contact interface. The interaction of oxides switches on CO oxidation at 55 °C and the synergistic effect of interaction also improves H2 oxidation at 95 °C. CO oxidation takes place at the contact interface of CeO2 and CuO. The high BET surface area and good dispersion of catalysts can be more helpful for the presence of accumulated long periphery at interface of CeO2 and CuO than the larger CeO2 particles when most of CeO2 particles pile into the small clusters and distribute on the bulk CuO. The CeO2/CuO catalyst with 1:2 Ce/Cu molar ratio has the highest BET surface area and better dispersion of CeO2 among the catalysts, therefore it display good catalytic activity, selectivity and stability. 相似文献
8.
CeO2–TiO2–ZrO2 thin films were prepared using the sol–gel process and deposited on glass and ITO-coated glass substrates via dip-coating technique. The samples were heat treated between 100 and 500 °C. The heat treatment effects on the electrochromic performances of the films were determined by means of cyclic voltammetry measurements. The structural behavior of the film was characterized by atomic force microscopy and X-ray diffraction. Refractive index, extinction coefficient, and thickness of the films were determined in the 350–1000 nm wavelength, using nkd spectrophotometry analysis.Heat treatment temperature affects the electrochromic, optical, and structural properties of the film. The charge density of the samples increased from 8.8 to 14.8 mC/cm2, with increasing heat-treatment temperatures from 100 to 500 °C. It was determined that the highest ratio between anodic and cathodic charge takes place with increase of temperature up to 500 °C. 相似文献
9.
Cheng-Chun Chang Ching-Tu Chang Shu-Jen Chiang Biing-Jye Liaw Yin-Zu Chen 《International Journal of Hydrogen Energy》2010
The composition (CuO/ZnO/Al2O3 = 30/60/10) of a commercial catalyst G66B was used as a reference for designing CuO/ZnO/CeO2/ZrO2/Al2O3 catalysts for the oxidative (or combined) steam reforming of methanol (OSRM). The effects of Al2O3, CeO2 and ZrO2 on the OSRM reaction were clearly identified. CeO2, ZrO2 and Al2O3 all promoted the dispersions of CuO and ZnO in CuO/ZnO/CeO2/ZrO2/Al2O3 catalysts. Aluminum oxide lowered the reducibility of the catalyst, and weakened the OSRM reaction. Cerium oxide increased the reducibility of the catalyst, but weakened the reaction. Zirconium oxide improved the reducibility of the catalyst, and promoted the reaction. A lower CuO/ZnO ratio of the catalyst was associated with greater promotion of ZrO2. The critical CuO/ZnO ratio for the promotion of ZrO2 was approximately 0.75–0.8. Introducing of ZrO2 into CuO/ZnO/Al2O3 also improved the stability of the catalyst. Although Al2O3 inhibited the OSRM reaction, a certain amount of it was required to ensure the stability and the mechanical strength of the catalysts. 相似文献
10.
A. Ennaoui B.R. Sankapal V. Skryshevsky M.Ch. Lux-Steiner 《Solar Energy Materials & Solar Cells》2006,90(10):1533-1541
Simple soft-solution method has been developed to synthesize films and powders of TiO2 and mixed TiO2–SiO2 at relatively low temperatures. This method is simple and inexpensive. Furthermore, reactor can be designed for large-scale applications as well as to produce large quantities of composite powders in a single step. For the preparation of TiO2, we used aqueous acidic medium containing TiOSO4 and H2O2, which results in a peroxo-titanium precursor while colloidal SiO2 has been added to the precursor for the formation of TiO2–SiO2. Post annealing at 500 °C is necessary to have anatase structure. Resulting films and powders were characterized by different techniques. TiO2 (anatase) phase with (1 0 1) preferred orientation has been obtained. Also in TiO2–SiO2 mixed films and powders, TiO2 (anatase) phase was found. Fourier transform infrared spectroscopy (FTIR) results for TiO2 and mixed TiO2–SiO2 films have been presented and discussed. The method developed in this paper allowed obtaining compact and homogeneous TiO2 films. These compact films are highly photoactive when TiO2 is used as photo anode in an photoelectrochemical cell. Nanoporous morphology is obtained when SiO2 colloids are added into the solution. 相似文献
11.
Álvaro Reyes-CarmonaAna Arango-Díaz Elisa MorettiAldo Talon Loretta StoraroMaurizio Lenarda Antonio Jiménez-LópezEnrique Rodríguez-Castellón 《Journal of power sources》2011,196(9):4382-4387
The application of the catalytic system CuO/CeO2 supported on Zr doped SBA-15 mesoporous silica to the preferential oxidation of CO on hydrogen streams (CO-PROX) suitable to be used to feed PEM fuel cells, has been studied. A loading of 20% (wt.) Ce and 6% (wt.) Cu was found optimal for the CO-PROX reaction. The influence of the presence of CO2 and H2O in the gas feed was also studied in order to simulate the real operation conditions of a PEMFC feed stream generated by alcohol steam reforming. The catalysts were characterized by XRD, adsorption-desorption of N2 at −196 °C, TEM, -H2-TPR and XPS. The system reducibility was found modified by the incorporation of zirconium in the support, with improvement of both the conversion and selectivity of the catalytic system, compared to the same material without Zr. 相似文献
12.
Shanghong Zeng Yan WangKewei Liu Fenrong LiuHaiquan Su 《International Journal of Hydrogen Energy》2012
The CuO supports with different morphology were prepared using the precipitation method. The inverse CeO2/CuO catalysts were synthesized by the impregnation method, and characterized via XRD, H2-TPR, SEM, TEM, XPS and N2 adsorption-desorption techniques. The study showed that CO oxidation took place at the interface of CeO2–CuO catalysts. The CeO2/CuO catalysts maintained their morphologies, structure and the length of periphery at the CeO2–CuO interface in the hydrogen-rich reaction gasses during the reaction. The two-dimensional and homogeneous petal morphology of support was most favorable for the formation of long periphery at the CeO2–CuO interface, therefore the CeO2 supported on the CuO with petal morphology presented good catalytic activity. 相似文献
13.
Enrique Snchez Mora Estela Gmez Barojas Esmeralda Rojas Rojas Rutilo Silva Gonzlez 《Solar Energy Materials & Solar Cells》2007,91(15-16):1412-1415
Morphological, optical and photocatalytic properties of TiO2, Fe2O3 and TiO2–Fe2O3 samples (formed by 1, 3 and 5 coatings) were studied. The layers were deposited on glass substrate by the sol–gel method. The catalytic activity of the samples was studied by the photodecomposition of methylene blue (MB) under visible light illumination. The FTIR results indicate that all samples present surface OH radicals that are bound either to the Ti or Fe atoms. This effect is better visualized at larger number of coatings in the TiO2–Fe2O3/glass systems. Also, two mechanisms are observed during the photodecomposition of the MB. 相似文献
14.
Yusheng She Qi Zheng Lei Li Yingying Zhan Chongqi Chen Yuanhui Zheng Xingyi Lin 《International Journal of Hydrogen Energy》2009,34(21):8929-8936
Water–gas shift reaction was carried out over a series of CuO/CeO2 catalysts doped with trivalent rare earth oxide (RE2O3, RE = Y, La, Nd and Sm), prepared via co-precipitation method. The effect of the dopants on the structure and catalytic properties of CuO/CeO2 catalysts was investigated with the aid of X-ray diffraction (XRD), Raman spectra, N2 physisorption, H2-TPR and selective N2O chemisorption characterizations. The results reveal the beneficial role of La2O3 and Nd2O3 doping in increasing the WGS catalytic activities and stabilities of CuO/CeO2 catalysts, while the addition of Y2O3 and Sm2O3 leads to the negative effect. Correlating to the characteristic results, it is found that the performance of CuO/CeO2–RE2O3 catalysts strongly depends on their surface copper dispersion, microstrain value and the amount of oxygen vacancies generated in ceria lattice. Besides, enough evidences suggest that, the most effective active site for WGS reaction is the moderate copper oxide (crystalline) interacted with surface oxygen vacancies of ceria in the CuO–CeO2 system. 相似文献
15.
A. Arango-Díaz J.A. Cecilia E. Moretti A. Talon P. Núñez J. Marrero-Jerez J. Jiménez-Jiménez A. Jiménez-López E. Rodríguez-Castellón 《International Journal of Hydrogen Energy》2014
CuO supported on CeO2, Ce0.8Zr0.2O2 and Ce0.8Al0.2O2 based catalysts (6%wt Cu) were synthesized and tested in the preferential oxidation of CO in a H2-rich stream (CO-PROX). Nanocrystalline supports, CeO2 and solid solutions of modified CeO2 with zirconium and aluminum were prepared by a freeze-drying method. CuO was supported by incipient wetness impregnation and calcination at 400 °C. All catalysts exhibit high activity in the CO-PROX reaction and selectivity to CO2 at low reaction temperature, being the catalyst supported on CeO2 the more active and stable. The influence of the presence of CO2 and H2O was also studied. 相似文献
16.
D. Gamarra A. Hornés Zs. Koppány Z. Schay G. Munuera J. Soria A. Martínez-Arias 《Journal of power sources》2007
Nanostructured catalysts based on combinations between oxidised copper and cerium entities prepared by two different methods (impregnation of ceria and coprecipitation of the two components within reverse microemulsions) have been examined with respect to their catalytic performance for preferential oxidation of CO in a H2-rich stream (CO-PROX). Correlations between their catalytic and redox properties are established on the basis of parallel analyses of temperature programmed reduction results employing both H2 and CO as reactants as well as by XPS. Although general catalytic trends can be directly correlated with the redox properties observed upon separate interactions with each of the two reductants (CO and H2), the existence of interferences between both reductants must be considered to complete details for such activity/redox correlation. Differences in the nature of the active oxidised copper–cerium contacts present in each case determine the catalytic properties of these systems for the CO-PROX process. 相似文献
17.
Shui-Yang Lien Dong-Sing Wuu Wen-Chang Yeh Jun-Chin Liu 《Solar Energy Materials & Solar Cells》2006,90(16):2710-2719
Antireflection coatings (ARCs) have become one of the key issues for mass production of Si solar cells. They are generally performed by vacuum processes such as thermal evaporation, reactive sputtering, and plasma-enhanced chemical vapor deposition. In this work, a sol–gel method has been demonstrated to prepare the ARCs for the non-textured monocrystalline Si solar cells. The spin-coated TiO2 single-layer, SiO2/TiO2 double-layer and SiO2/SiO2–TiO2/TiO2 triple-layer ARCs were deposited on the Si solar cells and they showed good uniformity in thickness. The measured average optical reflectance (400–1000 nm) was about 9.3, 6.2 and 3.2% for the single-layer, double-layer and triple-layer ARCs, respectively. Good correlation between theoretical and experimental data was obtained. Under a triple-layer ARC condition, a 39% improvement in the efficiency of the monocrystalline Si solar cell was achieved. These indicate that the sol–gel ARC process has high potential for low-cost solar cell fabrication. 相似文献
18.
mer Kesmez H. Erdem amurlu Esin Burunkaya Erturul Arpa 《Solar Energy Materials & Solar Cells》2009,93(10):1833-1839
Glass substrates were first coated with SiO2 and then TiO2 by dipping into sols which were prepared by two different methods involving complex formation and hydrolysis, using ethanol (EtOH) or butyl glycol (BG). Concentration of TiO2 in the sols was kept at 0.1 and 0.5 wt%. Prepared coatings were investigated by field-emission scanning electron microscope (FESEM), atomic force microscope (AFM), hazemeter, UV–visible spectrophotometer and goniometer. Rhodamine B (RhB) photodegradation tests were performed in order to evaluate photocatalytic activity. Application of SiO2 as the bottom layer increased the transmittance by 6% points, thereby compensated for the loss of transmittance caused by the TiO2 self-cleaning top layer. Pencil-hardness values of the obtained coatings were in 5B–3H range. TiO2 coatings obtained from sols containing 0.5% TiO2 and BG solvent represented the highest photocatalytic activity, with a rate constant of 0.44 ppm−1 h−1 and a half period of 5.5 h. Self-cleaning surfaces were obtained while maintaining the anti-reflectance. 相似文献
19.
Jie Sun Yuguang Wang Jigang Li Guoliang Xiao Ligong Zhang Hong Li Yulong Cheng Chunwen Sun Zhenxing Cheng Zhongchao Dong Liquan Chen 《International Journal of Hydrogen Energy》2010
Catalyst of nickle oxide based on flowerlike cerium microspheres with high dispersion was made to achieve simultaneous dehydrogenation of ethanol and water molecules on multi-active sites. XRD, 77 K N2 adsorption and FESEM were applied to analyse and observe the catalyst's structure, porosity and morphology. This special morphology catalyst represented novel stability more than 600 h for hydrogen production at low temperature ethanol steam reforming. Ethanol-water mixtures could be converted into H2 with average selectivity value of 61.5 mol.% and average ethanol conversion 95.0 mol.% at 350 °C, with GHSV∼1.0 × 105 h−1, low CO selectivity about average value of 2.1 mol.%, during 550 h reforming stability test. Catalytic parameters with respect to yield of H2, activity, selectivity towards hydrogen production and stability with time on stream were determined. 相似文献
20.
Zhenhao Xi Changjiang Li Lu Zhang Mingyang Xing Jinlong Zhang 《International Journal of Hydrogen Energy》2014
Cu2O/TiO2 nanoparticles were prepared by solvothermal method, which formed the heterostructure of Cu2O/TiO2. Due to the heterostructure, the H2 evolution rate under simulated solar irradiation was increasingly promoted. Meanwhile a certain amount of Cu particles which were confirmed by Transmission Electro Microscopy (TEM) and X-Ray Photoelectron Spectroscopy (XPS), formed on the surface of Cu2O/TiO2, and the photoactivity was accordingly further enhanced. The stabilized activity was maintained after many times irradiation. It is interesting that after a few hours irradiation the amount of Cu particles on the surface kept unchanged in the presence of Cu2O and TiO2. The Cu particles that formed during hydrogen generation reaction play a key role in the further enhancement of the hydrogen production activity. In this study, it is the first time to study the details on the formation of the stable ternary structure under simulated solar irradiation and their synergistic effect on the photoactivity of the water splitting. 相似文献