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1.
近年来工作温度在500 ̄700℃的中温固体氧化物燃料电池(IT-SOFC)受到广泛关注。稀土掺杂氧化铈尤其是钐、钆掺杂氧化铈在中温下的离子电导率远高于钇掺杂氧化锆(YSZ),是较为理想的IT-SOFC电解质材料。由于掺杂氧化铈难于烧结,不便于制备致密的电解质膜,通过提高掺杂氧化铈粉体细度来降低其烧结温度,是近年来该材料应用领域的一个研究热点。已有各种合成掺杂氧化铈纳米粉的报道,如采用共沉淀法、固态反应法、水热处理法、燃烧法、溶胶-凝胶法等等。其中碳酸盐共沉淀法由于具有成本低、设备简单以及合成粉体细度高等优点而倍受青睐。通…  相似文献   

2.
This study prepared a dense Sm‐doped ceria (SDC) and an SDC carbonate composite (abbreviated as SDC‐C). The latter was prepared by immersing porous SDC with a formula of (Ce0.8Sm0.2)O1.9 and a relative density of approximately 65‐70% into a molten mixture of carbonates containing 1:1 molar ratio of Li2CO3 and Na2CO3 at 500 °C. The relative density of the SDC‐C was close to 100%. In addition, SDC oxide without carbonates, which also has a relative density of close to 100%, was heat treated at 1600 °C. At 500 °C, the electrical conductivity and ionic transference number (ti) of the SDC oxide were 1.79(5) × 10?3 S·cm?1 and 0.99(2), respectively, such that electronic conduction could be disregarded. Increasing the temperature caused a gradual decrease in the ti of SDC. Following the addition of carbonates to SDC, the electrical conductivity reached 1.23(9) × 10?1 S·cm?1 at 500 °C. After 14 days (340 h), the electrical conductivity of the SDC‐C at 490 °C, leveled off at about 6 × 10?2 S·cm?1. SDC‐C could be used as a potential electrolyte in solid oxide fuel cells (SOFCs) at temperatures below 500 °C.  相似文献   

3.
Coal syngases of various CO/H2 ratios were used as the fuel over anode of solid oxide fuel cells. Anode materials of La0.58Sr0.4Co0.2Fe0.8O3?δ (LSCF)–gadolinia-doped ceria (GDC) composites and Ni-added LSCF–GDC were tested. The maximum power density of CO is higher than that of H2 and increases as the CO concentration in the CO + H2 mixture increases. As the LSCF content in the LSCF–GDC composites increases, the H2 reactivity increases but the CO reactivity decreases. The maximum power density of Ni-added LSCF–GDC is highest but the steady-state current density of LSCF–GDC can be higher than that of Ni-added LSCF–GDC via an induction period of activation.  相似文献   

4.
The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO2) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO2(111) thin films and CeO2 powders, and theoretical calculations of CeO2(111) surfaces with oxygen vacancies (Ov) at the surface and in the bulk. We show that, on a stoichiometric CeO2(111) surface, H2 dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO2−x samples, both films and powders, hydroxyls and hydrides (Ce−H) are formed on the surface as well as in the bulk, accompanied by the Ce3+ ↔ Ce4+ redox reaction. As the Ov concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H2/CeO2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.  相似文献   

5.
The two oxidation states of ceria nanoparticles, Ce3+ and Ce4+, play a pivotal role in scavenging reactive oxygen species (ROS). In particular, Ce3+ is largely responsible for removing O2 and .OH that are associated with inflammatory response and cell death. The synthesis is reported of 2 nm ceria–zirconia nanoparticles (CZ NPs) that possess a higher Ce3+/Ce4+ ratio and faster conversion from Ce4+ to Ce3+ than those exhibited by ceria nanoparticles. The obtained Ce0.7Zr0.3O2 (7CZ) NPs greatly improve ROS scavenging performance, thus regulating inflammatory cells in a very low dose. Moreover, 7CZ NPs are demonstrated to be effective in reducing mortality and systemic inflammation in two representative sepsis models. These findings suggest that 7CZ NPs have the potential as a therapeutic nanomedicine for treating ROS‐related inflammatory diseases.  相似文献   

6.
Solid oxide fuel cell (SOFC) unit was constructed with Ni–GDC (gadolinia-doped ceria) as the anode, YSZ as the electrolyte, and Cu-added La0.58Sr0.4Co0.2Fe0.8O3–δ–GDC as the cathode. Electrochemical CO2 reduction occurs. The CO formation rate, the CO2 conversion and the generated current density increase with increasing CO2 concentration and temperature. The CO2 conversion rate equals exactly the CO formation rate. No carbon deposition occurs. The activation energy is 2.72 kcal mol?1. The electrochemical CO2 reduction (dissociation) can have much lower activation barrier than the catalytic one. Simultaneous CO2 reduction with power generation in SOFCs can be feasible.  相似文献   

7.
As an exceptional Fenton-like reagent, cerium oxide (CeO2) finds applications in biomedical science and organic pollutants treatment. The Fenton-like reaction catalyzed by CeO2 typically encompasses two distinct processes: one resembling the classical Fenton reaction, wherein cerium (Ce3+) triggers the decomposition of hydrogen peroxide (H2O2) to yield reactive oxygen species (ROS), and the other involves the complexation of H2O2 on the Ce3+ surface, leading to the formation of peroxides. However, the influence of diverse CeO2 morphologies on these two reaction pathways has not been comprehensively explored. In this study, CeO2 exhibiting three typical morphologies, rods, cubes, and spheres, were prepared. The generation of ROS and peroxides was evaluated using the 3,3,5,5-tetramethylbenzidine (TMB) oxidation reaction and the reduction current of H2O2, respectively. Moreover, the impacts of pH variations and CeO2/H2O2 concentrations on the production and conversion of these two reaction products were investigated. To corroborate the distinctions between the resultant products and their applicability, apoptosis assays and acid orange 7 (AO7) degradation analyses were performed. Notably, CeO2 rods exhibited the highest proportion of Ce3+, predominantly engaging in complexation with H2O2 to foster peroxide formation, thereby facilitating the robust degradation of AO7. However, the generated peroxides appeared to occupy Ce3+ sites, thereby impeding the H2O2 decomposition process. Conversely, Ce3+ species on the surface of CeO2 cubes were primarily involved in H2O2 decomposition, leading to heightened ROS production, and thus showcasing substantial potential for damaging A549 tumor cells. It is worth noting that the ability of these Ce3+ species to form peroxides through complexation with H2O2 was comparatively reduced. In summation, this study sheds light on the intricate interplay between distinct CeO2 morphologies and their divergent impacts on Fenton-like reactions. These findings expand our comprehension of the influences on its reactivity of CeO2 morphologies and open new insights for applications in diverse domains, from organic dye degradation to tumor therapy.  相似文献   

8.
The interaction of hydrogen with reduced ceria (CeO2?x) powders and CeO2?x(111) thin films was studied using several characterization techniques including TEM, XRD, LEED, XPS, RPES, EELS, ESR, and TDS. The results clearly indicate that both in reduced ceria powders as well as in reduced single crystal ceria films hydrogen may form hydroxyls at the surface and hydride species below the surface. The formation of hydrides is clearly linked to the presence of oxygen vacancies and is accompanied by the transfer of an electron from a Ce3+ species to hydrogen, which results in the formation of Ce4+, and thus in oxidation of ceria.  相似文献   

9.
Diammonium carbonate hydrogen peroxide monosolvate, 2NH4+·CO32−·H2O2, (I), and dicaesium carbonate hydrogen peroxide trisolvate, 2Cs+·CO32−·3H2O2, (II), were crystallized from 98% hydrogen peroxide. In (I), the carbonate anions and peroxide solvent molecules are arranged on twofold axes. The peroxide molecules act as donors in only two hydrogen bonds with carbonate groups, forming chains along the a and c axes. In the structure of (II), there are three independent Cs+ ions, two of them residing on twofold axes, as are two of the four peroxide molecules, one of which is disordered. Both structures comprise complicated three‐dimensional hydrogen‐bonded networks.  相似文献   

10.
Solid-oxide fuel cells (SOFCs) can be used for clean, efficient and environment-friendly energy conversion with a variety of fuels at high temperature (1273 K). The high temperature operation accelerates unwanted reactions and creates materials challenges; so, intermediate-temperature SOFCs (IT-SOFCs) have been developed. Reduction of the operating temperature (between 873–1073 K) requires solid electrolyte materials with higher conductivities. In this study, partially substituted ceria as solid electrolyte is experimented systematically for use in solid oxide fuel cells operating below 1073 K (intermediate temperature range). Nine compositions namely, CeO2, Ce0.95Gd0.05O2-δ (CGO9505), Ce0.90Gd0.10O2-δ (CGO9010), Ce0.85Gd0.15O2-δ (CGO8515), Ce0.80Gd0.20O2-δ (CGO8020), Ce0.95Sm0.05O2-δ (SDC9505), Ce0.90Sm0.10O2-δ (SDC9010), Ce0.85Sm0.15O2-δ (SDC8515) and Ce0.80Sm0.20O2-δ (SDC8020) were synthesized by Glycine Nitrate (GN) combustion technique and investigated. The physical properties and the other relevant features of the data obtained are analyzed with a view to use these alternate electrolyte materials in IT-SOFC.  相似文献   

11.
It has been ascertained that the electrochemically deposited thin films of cerium oxides, containing mainly CeO2 and also some insignificant amount of Ce2O3, are acting as an effective cathodic coating, leading to restoration of the passive state of the studied stainless steel (OC 404) samples. This effect is associated with a strong shifting of the stationary corrosion potential of the steel in positive direction, moving over from potentials characteristic of corrosion in active state to potentials falling within the zone of passivity. In this respect, another basic purpose of the investigations was the elucidation of the mechanism of action of the cerium oxide film and in particular collecting experimental evidence for the supposition about the occurrence of an efficient depolarization reaction of CeO2 reduction (resulting in a state of passivity—improved ability of self-passivation) instead of hydrogen depolarization reaction. For this purpose, we considered also the decrease in the surface concentration of ceria in the passive layer under the conditions of the actual corrosion process (self-dissolution) of the stainless steel by means of XPS, SEM, ICP-AES, and gravimetric analyses. A decrease in the surface concentration of CeO2 (Ce4+) has been observed, which is known to be chemically inert in acidic media. The obtained results prove the occurrence of an effective cathodic process of Ce4+ (CeO2) reduction into Ce3+ (soluble in acids Ce2O3 ) in the superficial oxide film.  相似文献   

12.
尉继英  范桂芳  江锋  张振中  张兰 《催化学报》2010,31(12):1489-1495
 采用沉积沉淀法制备了 CO 低温氧化催化剂 Au/α-Fe2O3, 通过 X 射线衍射、X 射线光电子能谱、N2 吸附-脱附、傅里叶变换红外光谱、H2 程序升温还原和 CO2 程序升温脱附等手段对催化剂进行了表征, 探讨了在室温大气气氛下光线照射以及表面吸附等环境因素所导致的催化剂存贮失活及其作用机理. 结果表明, 经 110 oC 干燥的 Au/α-Fe2O3催化剂表面同时存在 Au3+和 Auδ+ (0 ≤ δ ≤ 1) 物种, 且前者催化 CO 氧化的活性更高; 在室温大气气氛下, 紫外线照射会引起 Au3+的还原和 Au 颗粒的生长, 导致催化剂的不可逆失活. 此外, 空气中的 H2O 和 CO2 可同时吸附在 α-Fe2O3的表面, 形成表面碳酸盐物种, 会引起催化剂的可逆失活.  相似文献   

13.
乙二醇溶剂热合成的CeO2的可逆氧化还原性及CO2捕获性能   总被引:1,自引:0,他引:1  
利用乙二醇的还原性,采用乙二醇溶剂热法制备了表面具有丰富氧空穴的CeO2-GST纳米晶,对其进行了X射线衍射、透射电镜、X射线光电子能谱、原位H2还原-O2氧化循环和CO2原位红外漫反射表征,并研究了其可逆氧化还原性及CO2捕获性能. 结果表明,与CeO2-nanorod和柠檬酸溶胶法合成的CeO2-CA样品相比,CeO2-GST纳米晶具有最好的可逆氧化还原性能和循环稳定性,同时在50 ℃下具有最好的CO2吸附性能(149 μmol/g). 利用原位红外漫反射光谱研究了CO2在还原CeO2表面的吸附情况,发现CO2主要以双齿碳酸盐和桥连碳酸盐两种形式吸附在CeO2表面,其中桥连碳酸盐物种不稳定,He吹扫可脱附. 此外,CO2在CeO2-nanorod上还会生成稳定的甲酸盐和单齿碳酸盐物种.  相似文献   

14.
The reduction of chromium, nickel, and manganese oxides by hydrogen, CO, CH4, and model syngas (mixtures of CO + H2 or H2 + CO + CO2) and oxidation by water vapor has been studied from the thermodynamic and chemical equilibrium point of view. Attention was concentrated not only on the convenient conditions for reduction of the relevant oxides to metals or lower oxides at temperatures in the range 400–1000 K, but also on the possible formation of soot, carbides, and carbonates as precursors for the carbon monoxide and carbon dioxide formation in the steam oxidation step. Reduction of very stable Cr2O3 to metallic Cr by hydrogen or CO at temperatures of 400–1000 K is thermodynamically excluded. Reduction of nickel oxide (NiO) and manganese oxide (Mn3O4) by hydrogen or CO at such temperatures is feasible. The oxidation of MnO and Ni by steam and simultaneous production of hydrogen at temperatures between 400 and 1000 K is a difficult step from the thermodynamics viewpoint. Assuming the Ni—NiO system, the formation of nickel aluminum spinel could be used to increase the equilibrium hydrogen yield, thus, enabling the hydrogen production via looping redox process. The equilibrium hydrogen yield under the conditions of steam oxidation of the Ni—NiO system is, however, substantially lower than that for the Fe—Fe3O4 system. The system comprising nickel ferrite seems to be unsuitable for cyclic redox processes. Under strongly reducing conditions, at high CO concentrations/partial pressures, formation of nickel carbide (Ni3C) is thermodynamically favored. Pressurized conditions during the reduction step with CO/CO2 containing gases enhance the formation of soot and carbon-containing compounds such as carbides and/or carbonates.  相似文献   

15.
Crystalline cerium oxide carbonate hydrate (Ce2O(CO3)2·H2O) was grown in aqueous solutions at a low temperature of 80 °C under ambient pressure. When cerium nitrate was used as a starting material, large Ce2O(CO3)2·H2O particles were precipitated through homogeneous nucleation and subsequent fast crystal growth. In contrast, the usage of cerium chloride was found to promote the preferential precipitation of Ce2O(CO3)2·H2O on foreign substrates through heterogeneous nucleation and slow crystal growth. This phenomenon was applied to a chemical bath deposition of Ce2O(CO3)2·H2O films. Immersion of glass substrates in the solution at 80 °C for typically 24 h resulted in formation of solid films with a unique morphology like a micrometer-scale brush. It was also found that samarium could be incorporated into Ce2O(CO3)2·H2O during the crystal growth in the solutions, as evidenced by characteristic photoluminescence of Sm3+ in heating products of CeO2. These results suggest that rare-earth oxide carbonate hydrates with a variety of compositions and morphologies can be synthesized from the aqueous solutions.  相似文献   

16.
A sol–gel route to synthesize nanocrystalline praseodymium-, samarium- and gadolinium-doped ceria powders for solid oxides fuel Cells SOFCs is presented. The method involves metal nitrates with propionic acid (both as chelating ligand and solvent), gel formation, liquid nitrogen quenching, drying at 150 °C/24 h, and finally decomposition at 450 °C in nitrogen followed by calcination at 650 °C in air. TG–DTA, BET, XRD, FTIR, UV–vis and catalytic tests were used to characterize the samples. Ce0.8Pr0.2O2?δ sample exhibited the best catalytic performance in methane steam reforming under water deficient conditions, closely followed by Ce0.9Gd0.1O2?δ, Ce0.8Sm0.2O2?δ and Ce0.8Gd0.2O2?δ catalysts. The superior catalytic performance of Ce0.8Pr0.2O2?δ sample was attributed to the existence of praseodymium species (Pr4+/Pr3+) strongly interacting with ceria. The two systems act synergistically in the catalytic steam reforming of methane.  相似文献   

17.
Ce2Sn2O7 pyrochlore was synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition and valence state of the sample. The oxygen exchange property of the Ce2Sn2O7 phase was measured by an oxidation reaction in sealed air atmosphere and a followed reduction reaction in 5% H2-95% N2 atmosphere. Gas chromatography (GC) was used to analyze the oxygen change in the reaction. The results show that Ce2Sn2O7 sample has excellent oxygen absorption capacity at 250°C as Ce3+ ions are oxidized to Ce4+ ions. The oxidized sample can be reduced by 5% H2-95% N2. The refreshed sample remains the capacity of oxygen absorption, while the oxygen exchange capacity degrades with the reduction times.  相似文献   

18.
A series of ceria-based composite materials consisting of samaria doped ceria (SDC) and binary carbonates(Li2CO3–Na2CO3) were examined as functional electrolytes for low-temperature solid oxide fuel cells (SOFCs). DTA and SEM techniques were applied to characterize the phase- and micro-structural properties of the composite materials. Conductivity measurements were carried on the composite electrolytes with a.c. impedance in air. A transition of ionic conductivity with temperature was occurred among all samples with different carbonate content, which related to the interface phase. Single cells based on the composite electrolytes, NiO as anode and lithiated NiO as cathode, were fabricated by a simple dry-pressing process and tested at 400–600 °C. The maximum output power at 600 °C increased with the carbonate content in the composite electrolytes, and reached the maximum at 25 wt.%, then decreased. Similar trend has also shown at 500 °C, but the maximum was obtained at 20wt.%. The best performances of 1085 mW cm−2 at 600 °C and 690 mW cm−2 at 500 °C were achieved for the composite electrolytes containing 25 and 20 wt.% carbonates, respectively. During fuel cell operation, it found that the SDC-carbonate composites are co-ionic (O2−/H+) conductors. At lower carbonate contents, both oxide–ion and proton conductions were significant, when the content increased to 20–35 wt.%, proton conduction dominated. The detailed conduction mechanism in these composites needs further investigation.  相似文献   

19.
Polysulfone (PSF) and sulfonated polysulfone (SPSF) were synthesized and characterized by IR spectrum. Sm1.5Sr0.5NiO4 (SSN) and Ni‐Ce0.8Sm0.2O2?δ (Ni‐SDC, Ni‐samarium doped ceria) were prepared and characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was synthesized from wet hydrogen and dry nitrogen with applied voltage, using SSN as cathode, Ni‐SDC as anode, Nafion and SPSF as proton membrane respectively. The performances of Nafion and SPSF membranes in ammonia synthesis were investigated and compared at atmospheric pressure and low temperature (25–100°C). The results demonstrated that the proton conducting performances of Nafion and SPSF membranes were similar and the highest rates of evolution of ammonia were up to 1.05×10?8 and 1.03×10?8 mol·cm?2·s?1 respectively at 80°C and 2.5 V.  相似文献   

20.
The normal carbonates of La3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ and Ho3+ have been synthesized by the reaction of an aqueous suspension of the lanthanide oxide, M2O3, with CO2 under supercritical conditions. The effect of temperature, between 25 and 50 °C, and pressure, from 68 to 240 atm, on the extent of conversion of the oxide to the carbonate has been investigated. Yields of 95% or better of the normal carbonates were obtained at a pressure of 100 atm after the reaction was carried out for 1 h. The higher the concentration of CO2 dissolved in the aqueous phase, the higher the yield. The oxides of Pr3+, Tb3+, Er3+ and Yb3+, as well as ZrO2 and CeO2, either did not react at all or gave very low yields of carbonates under the experimental conditions that were employed.  相似文献   

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