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1.
To investigate the mechanisms of the improvement on separation efficiency of photogenerated carriers, a Fe2O3/SrTiO3 heterojunction semiconductor with an improved separation efficiency was successfully prepared. The heterojunction semiconductor was characterized with X-ray diffraction (XRD), UV–vis absorption spectrum, scanning electron microscope (SEM) and surface photovoltage (SPV) spectroscopy. The energy band diagrams of Fe2O3 and SrTiO3 were determined with X-ray photoelectron spectroscopy (XPS), based on which the conduction band offset (CBO) between Fe2O3 and SrTiO3 was quantified to be 1.26 ± 0.03 eV. The recombination of photogenerated carriers was investigated with photoluminescence (PL) spectrum, which indicates that the formation of Fe2O3/SrTiO3 decreases the recombination. Thus the improved separation efficiency is mainly due to the energy difference between the conduction band edges of Fe2O3 and SrTiO3, and the decreased electron-hole recombination for Fe2O3/SrTiO3. 相似文献
2.
Bilayer photoanodes were prepared onto glass substrates (FTO) in order to improve generated photocurrents using UV-vis light by water splitting process. A comparative study of photocatalytic was performed over the films surface using Fe2O3, WO3 and mixture of bicomponents (Fe2O3:WO3). Different types of films were prepared using Fe2O3, WO3 and bicomponents (mixture) on FTO substrates. The films were grown by sol gel method with the PEG-300 as the structure-directing agent. The photo-generated of the samples were determined by measuring the currents and voltages under illumination of UV-vis light. The morphology, structure and related composition distribution of the films have been characterized by SEM, XRD and EDX respectively. Photocurrent measurements indicated surface roughness as the effective parameter in this study. The deposited surfaces by bicomponents or mixture are flat without any feature on the surface while the deposited surfaces by WO3 appears rough surface as small round (egg-shaped particles) and cauliflower-like. The surface deposited by Fe2O3 show rough no as well as WO3 surface. The deposited surfaces by WO3 reveal the higher value of photocurrent measurement due to surface roughness. Indeed, the roughness can be effective in increasing contact surface area between film and electrolyte and diffuse reflection (light scattering effect). The solution (Fe2O3:WO3) shows the low photocurrent value in compare to WO3 and Fe2O3 hat it may be due to decomposition the compound at 450 ± 1 °C to iron-tungstate Fe2(WO4)3. 相似文献
3.
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
4.
We successfully fabricated cost-effective and efficient pulse electrodeposited Fe2O3 photoanodes for PEC water splitting application. Surface modifications of Fe2O3 by oxygen evolution catalysts like cobalt phosphate (Co–Pi), a monoclinic BiVO4 or both showed cathodic/anodic shift in photocurrent with significantly improved photo-response. 相似文献
5.
Functional carbon nanotubes (CNTs) were incorporated into Ti-doped Fe2O3 thin films by a facile, one-step co-electrodeposition method. The films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible absorption, and X-ray photoelectron spectroscopy. The introduction of CNTs results in a better absorption in visible region and greatly enhances the photoelectrochemical properties of the Ti–Fe2O3 films. The improved photoelectrochemical properties of the CNTs and Ti co-doped Fe2O3 films are due to the charge equilibration which interplays between the Ti–Fe2O3 and CNTs. The effect of CNTs to mediate fast charge transfer and to retard charge recombination rate in the composites is also demonstrated by kinetics analysis and electrochemical impedance spectroscopy. The influence of different groups-modified CNTs and different content of CNTs was also studied. The highest photocurrent is 4.5 mA/cm2 at 1.23 V (vs. RHE) obtained by incorporating 0.10 mg/mL amino-group modified CNTs in the Ti–Fe2O3 film. The amino-functionalized CNTs doped film exhibits the highest photoelectric response compared with those doped by the pristine and acid-treated CNTs under the same conditions, which can be ascribed to the better hydrophilicity and dispersibility of the amino-functionalized CNTs. 相似文献
6.
Novel photocatalysts, which consist of two visible light responsive semiconductors including graphite-like carbon nitride (g-C3N4) and Fe2O3, were successfully synthesized via electrodeposition followed by chemical vapor deposition. The morphology of the g-C3N4/Fe2O3 can be tuned from regular nanosheets to porous cross-linked nanostructures. Remarkably, the optimum activity of the g-C3N4/Fe2O3 is almost 70 times higher than that of individual Fe2O3 for photoelectrochemical water splitting. The enhancement of photoelectrochemical activity could be assigned to the morphology change of the photocatalysts and the effective separation and transfer of photogenerated electrons and holes originated from the intimately contacted interfaces. The g-C3N4/Fe2O3 composites could be developed as high performance photocatalysts for water splitting and other optoelectric devices. 相似文献
7.
The hydrogen photo-evolution was successfully achieved in aqueous (Fe1−xCrx)2O3 suspensions (0 ≤ x ≤ 1). The solid solution has been prepared by incipient wetness impregnation and characterized by X-ray diffraction, BET, transport properties and photo-electrochemistry. The oxides crystallize in the corundum structure, they exhibit n-type conductivity with activation energy of ∼0.1 eV and the conduction occurs via adiabatic polaron hops. The characterization of the band edges has been studied by the Mott Schottky plots. The onset potential of the photo-current is ∼0.2 V cathodic with respect to the flat band potential, implying a small existence of surface states within the gap region. The absorption of visible light promotes electrons into (Fe1−xCrx)2O3-CB with a potential (∼−0.5 VSCE) sufficient to reduce water into hydrogen. As expected, the quantum yield increases with decreasing the electro affinity through the substitution of iron by the more electropositive chromium which increases the band bending at the interface and favours the charge separation. The generated photo-voltage was sufficient to promote simultaneously H2O reduction and SO32− oxidation in the energetically downhill reaction (H2O + SO32− → H2 + SO42−, ΔG = −17.68 kJ mol−1). The best activity occurs over Fe1.2Cr0.8O3 in SO32− (0.1 M) solution with H2 liberation rate of 21.7 μmol g−1 min−1 and a quantum yield 0.06% under polychromatic light. Over time, a pronounced deceleration occurs, due to the competitive reduction of the end product S2O62−. 相似文献
8.
Na-Ri Lee Soo-Sun Lee Kyoeng-Il Kim Whan-Gi Kim Hyunchul Ju Dong Min Kim Tae-Whan Hong 《International Journal of Hydrogen Energy》2013
Ceramic membrane has high permeation rate of hydrogen and chemical stability. Al2O3 indicates stable at high temperature and a relatively large surface area. In addition, Al2O3 of porous is used as hydrogen separation membranes support, because of the high hydrogen permeability based on Knudsen diffusion mechanism. 相似文献
9.
Selective catalytic reduction (SCR) of NO from simulated flue gas by ammonia with Fe2O3 particles as the catalyst was performed using a magnetically fluidized bed (MFB). X-ray diffraction (XRD) spectroscopy and Brunauer–Emmett–Teller (BET) method were used to analyze Fe2O3 catalyst. Important effects of magnetic fields were observed in the SCR of NO by ammonia over Fe2O3 catalyst. The apparent activation energies of SCR were reduced by external magnetic fields, and the SCR activity of Fe2O3 catalyst was improved with the magnetic fields at low temperatures. Thus the scope of temperature with high efficiency of NO removal was extended from 493–523 K to 453–523 K by magnetic fields. Magnetic fields of 0.01–0.015 T were suggested for NO removal on Fe2O3 catalyst with MFB. The results suggested that the magnetoadsorption of NO onto Fe2O3 surface together with NH2 and NO free radicals effects induced by the external magnetic fields both acted to improve the rate of SCR of NO on Fe2O3 catalyst. On the other hand, magnetic field effects were also attributed to improved gas–solid contact in MFB. 相似文献
10.
Zheng Xueping Xiao GuoLiu Shenglin Feng XinZheng Jiaojiao 《International Journal of Hydrogen Energy》2012
This study investigated the effect of Nd2O3 and Gd2O3 as catalyst on hydrogen desorption behavior of NaAlH4. Pressure-content-temperature (PCT) equipment measurement proved that both two oxides enhanced the dehydrogenation kinetics distinctly and increasing Nd2O3 and Gd2O3 from 0.5 mol% to 5 mol% caused a similar effect trend that the dehydrogenation amount and average dehydrogenation rate increased firstly and then decreased under the same conditions. 1 mol% Gd2O3–NaAlH4 presented the largest hydrogen desorption amount of 5.94 wt% while 1 mol% Nd2O3–NaAlH4 exerted the fastest dehydrogenation rate. Scanning Electron microscopy (SEM) analysis revealed that Gd2O3–NaAlH4 samples displayed uniform surface morphology that was bulky, uneven and flocculent. The difference of Nd2O3–NaAlH4 was that with the increasing of Nd2O3 content, the particles turned more and more big. Compared to dehydrogenation behavior, this phenomenon demonstrated that small particles structure were beneficial to hydrogen desorption. Besides, the further study found that different catalysts and addition amounts had different effects on the microstructure of NaAlH4. 相似文献
11.
Agnieszka Marty?a Barbara OlejnikPiotr Kirszensztejn Robert Przekop 《International Journal of Hydrogen Energy》2011,36(14):8358-8364
Three series of binary oxide systems B2O3/Al2O3 were prepared and the effect of alumina on dispersion of boron (B2O3) component was investigated. The aim of the study was to achieve a maximum dispersion of B2O3 in the Al2O3 a gel matrix that would lead to increased sorption capacity on boron oxide. Many attempts were made to establish the preparation conditions that would lead to a maximum dispersion of B2O3 in the Al2O3 gel matrix needed to increase the hydrogen sorption capacity on boron oxide. The systems were characterized by X-ray diffraction, SEM, TEM and low temperature nitrogen adsorption. Hydrogen adsorption was tested in the volumetric system.Results of the study showed that the amount of hydrogen adsorbed on B2O3 depended not only on the surface area of the system but also on the separation of B2O3 domains in Al2O3 gel network. Irrespective of the method of synthesis of the binary oxide system, the dispersion of B2O3 phase reflected in the amount of hydrogen adsorbed was the highest for the systems of the lowest B/Al molar ratios studied, i.e. for B/Al = 0.25. 相似文献
12.
Pt–Cu catalysts supported on Al2O3 and Nb2O5 were studied for use in selective CO oxidation. The addition of copper enhanced the activity and selectivity of Pt–Cu/Nb2O5 at lower temperatures when compared to Pt/Nb2O5. On the other hand, copper addition was not beneficial in the case of Al2O3 supported catalysts. 相似文献
13.
Ying Wang Li Wang Ning Gan Zi-Yian Lim Chunzheng Wu Jun Peng Wei Guo Wang 《International Journal of Hydrogen Energy》2014
Ni/xY2O3–Al2O3 (x = 5, 10, 15, 20 wt%) catalysts were prepared by sequential impregnation synthesis. The catalytic performance for the autothermal reforming of methane was evaluated and compared with Ni/γ-Al2O3 catalyst. The physicochemical properties of catalysts were characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM), X-Ray Photoelectron Spectrometer (XPS), Thermo Gravimetric Analyzer (TGA) and H2-temperature programmed reduction techniques (TPR). The decrease of nickel particle size and the change of reducibility were found with Y modification. The CH4 conversion increased with elevating levels of Y2O3 from 5% to 10%, then decreased with Y content from 10% to 20%. Ni/xY2O3–Al2O3 catalysts maintained high activity after 24 h on stream, while Ni/Al2O3 had a significant deactivation. The characterization of spent catalysts indicated that the addition of Y retarded Ni sintering and decreased the amount of coke. 相似文献
14.
Stability and efficiency of photocatalysts are important to realize the practical applications of them for photocatalytic hydrogen production from industrial sulfide effluent. Novel, magnetically separable core–shell nano photocatalysts viz., CdS/Fe2O3, ZnS/Fe2O3 and (CdS + ZnS)/Fe2O3 were prepared and their hydrogen evolution activity under visible light was examined. The XRD result shows that CdS and ZnS were very well coated on the surface of the iron oxide core shell particles. The HR-TEM result also confirms the core shell formation. (CdS + ZnS)/Fe2O3 evolved higher volume of hydrogen than the other catalysts. It is ascribed to rapid migration of excited electrons from (CdS + ZnS) toward Fe2O3 suppressing electron hole annihilation compared to other catalysts. The catalysts can be easily recovered from the reaction medium using external magnetic bar and so the photocatalyst can be reused without any mass loss. Hence, it can be a potential catalyst for recovery of hydrogen from industrial sulfide containing waste streams. 相似文献
15.
Prasad Manjusri Sirimanne Satoshi Shiozaki Noriyuki Sonoyama Tadayoshi Sakata 《Solar Energy Materials & Solar Cells》2000,62(3)
Microcrystals of In2S3 were formed on sintered In2O3 pellets by sulfurizing in H2S atmosphere. The flat band potential of compound In2S3|In2O3 electrodes was evaluated as −1.0 V vs Ag|AgCl in 1 M KOH, 1 M Na2S, 10−2 M S. Significantly enhanced photocurrent was observed on compound In2S3|In2O3 electrodes with a lower degree of sulfurization to that of compound In2S3|In2O3 electrodes with higher degree of sulfurization. Photocurrent generation of compound In2S3|In2O3 electrodes was explained from the viewpoint of semiconductor sensitization. 相似文献
16.
Myoung Youp Song Sung Nam KwonJean-Louis Bobet Hye Ryoung ParkDaniel R. Mumm 《International Journal of Hydrogen Energy》2011,36(5):3521-3528
Among samples of Mg-Ni, Mg-Ni-5Fe2O3, and Mg-Ni-5Fe, Mg-Ni-5Fe had the highest hydriding and dehydriding rates. For the as-milled Mg-Ni-5Fe alloy and the hydrided Mg-Ni-5Fe alloy after activation, the weight percentages of the constituent phases were calculated using the FullProf program. The creation of defects and the diminution of Mg particle size through reactive mechanical grinding and hydriding-dehydriding cycling, and the formation of the Mg2Ni phase are considered to increase the hydriding and dehydriding rates. Mg-14Ni-2Fe-2Ti-2Mo had higher hydriding and dehydriding rates than did any of the other samples (Mg-Ni, Mg-Ni-5Fe2O3, Mg-Ni-5Fe, and Mg-14Ni-6Fe2O3) prepared in this work. 相似文献
17.
Nilgün
zer John P. Cronin Yong-Jin Yao Antoni P. Tomsia 《Solar Energy Materials & Solar Cells》1999,59(4):355
Highly transparent, uniform and corrosion resistant Al2O3 films were prepared on stainless-steel and quartz substrates by the sol–gel process from stable coating solutions using aluminum-sec-butoxide, Al(OBus)3 as precursor, acetylacetone, AcAcH as chelating agent and nitric acid, HNO3, as catalyzer. Films up to 1000 nm thick were prepared by multiple spin coating deposition, and were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), optical spectroscopy and micro Vickers hardness test. XRD of the film heat treated at 400°C showed that they had an amorphous structure. XPS confirmed that they were stoichiometric Al2O3. The refractive index (n) and extinction coefficient (k) were found to be n=1.56±0.01 and k=0.003±0.0002 at 600 nm, respectively. The surface microhardness and corrosion resistance investigations showed that Al2O3 films improved the surface properties of stainless-steel substrates. 相似文献
18.
Nano-sized Fe2O3-loaded carbon material was prepared by loading Fe2O3 on carbon using various carbonaceous materials. Carbonaceous materials strongly affected the electrochemical behavior of nano-sized Fe2O3-loaded carbon. Among the carbons used, nano-carbons such as acetylene black (AB), tubular carbon nanofibers (CNF), and platelet CNF provided larger capacities than other carbons. This may be due to the greater surface area of nano-carbon, which gives a greater distribution of nano-sized Fe2O3 particles than other carbons and delivers a greater capacity than other carbons. Investigation of the first-cycle materials by X-ray photoelectron spectroscopy (XPS) revealed that Fe2O3 was reduced to Fe metal in the charge process (reduction of Fe2O3), and, conversely, Fe metal was not completely oxidized to Fe2O3 during discharge (oxidation of Fe). This result may be due to the covering of non-conductive Li2O formed during charging. 相似文献
19.
Myoung Youp Song Young Jun Kwak Byung-Soo Lee Hye Ryoung Park Byoung-Goan Kim 《International Journal of Hydrogen Energy》2012
Ni, Fe2O3, and CNT were added to Mg. The content of the additives was about 20 wt % with that of Fe2O3 6 wt%. The contents of about 20 wt % additives and 6 wt% Fe2O3 are known optimum ones to improve the reaction rates of Mg with H2. Samples with compositions of 80 wt% Mg–14 wt% Ni–6 wt% Fe2O3 (named as Mg–14Ni–6Fe2O3), and 78 wt% Mg–14 wt% Ni–6 wt% Fe2O3–2 wt% CNT (named as Mg–14Ni–6Fe2O3–2CNT) were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of these samples were then measured, and the effects of Ni, Fe2O3, and CNT addition on the hydriding and dehydriding rates of Mg-based alloys were investigated by comparing their hydrogen-storage properties with those of pure Mg and Mg–10 wt% Fe2O3. 相似文献
20.
S. Therdthianwong N. SrisiriwatA. Therdthianwong E. Croiset 《International Journal of Hydrogen Energy》2011,36(4):2877-2886
Bioethanol was reformed in supercritical water (SCW) at 500 °C and 25 MPa on Ni/Al2O3 and Ni/CeZrO2/Al2O3 catalysts to produce high-pressure hydrogen. The results were compared with non-catalytic reactions. Under supercritical water and in a non-catalytic environment, ethanol was reformed to H2, CO2 and CH4 with small amounts of CO and C2 gas and liquid products. The presence of either Ni/Al2O3 or Ni/CeZrO2/Al2O3 promoted reactions of ethanol reforming, dehydrogenation and decomposition. Acetaldehyde produced from the decomposition of ethanol was completely decomposed into CH4 and CO, which underwent a further water-gas shift reaction in SCW. This led to great increases in ethanol conversion and H2 yield on the catalysts of more than 3-4 times than that of the non-catalytic condition. For the catalytic operation, adding small amounts of oxygen at oxygen to ethanol molar ratio of 0.06 into the feed improved ethanol conversion, at the expense of some H2 oxidized to water, resulting in a slightly lower H2 yield. The ceria-zirconia promoted catalyst was more active than the unpromoted catalyst. On the promoted catalyst, complete ethanol conversion was achieved and no coke formation was found. The ceria-zirconia promoter has important roles in improving the decomposition of acetaldehyde, the enhancement of the water-gas shift as well as the methanation reactions to give an extremely low CO yield and a tremendously high H2/CO ratio. The SCW environment for ethanol reforming caused the transformation of gamma-alumina towards the corundum phase of the alumina support in the Ni/Al2O3 catalyst, but this transformation was slowed down by the presence of the ceria-zirconia promoter. 相似文献