C/H/O/N/S/Cl/K/Na元素的详细化学反应机理的简化与验证

基于Senkin模型,应用自编化学反应机理简化程序,结合Kinalc和Mechmod开源程序,发展了详细化学反应机理的简化与验证方法.以电站锅炉燃烧的计算流体力学(CFD)数值模拟为应用背景,建立了考虑C/H/O/N/S/Cl/K/Na元素的详细化学反应机理(115组分,1,342基元反应),并运用此方法得到简化反应机理(28组分,20反应).验证结果表明,该简化机理在锅炉运行的主要参数变化范围内(温度T=1,100～1,500,℃,过量空气系数λ=0.8～1.2)具有较好的准确性和较高的计算效率,可应用于锅炉燃烧的CFD计算.     

Hydrogen production from ethanol steam reforming over core–shell structured NixOy–, FexOy–, and CoxOy–Pd catalysts

The present work focused on the investigation of the hydrogen generation through the ethanol steam reforming over the core–shell structured Ni_xO_y–, Fe_xO_y–, and Co_xO_y–Pd loaded Zeolite Y catalysts. The transmission electron microscopy (TEM) image of Ni_xO_y–Pd represented a very clear core–shell structure, but the other two catalysts, Co_xO_y– and Fe_xO_y–Pd, were irregular and non-uniform. The catalytic performances differed according to the added core metal and the support. The core–shell structured Co_xO_y–Pd/Zeolite Y provided a significantly higher reforming reactivity compared to the other catalysts. The H₂ production was maximized to 98% over Co_xO_y–Pd(50.0 wt%)/Zeolite Y at the conditions of reaction temperature 600 °C, CH₃CH₂OH:H₂O = 1:3, and GHSV (gas hourly space velocity) 8400 h⁻¹. In the mechanism that was suggested in this work, the cobalt component played an important role in the partial oxidation and the CO activation for acetaldehyde and CO₂ respectively, and eventually, cobalt increased the hydrogen yield and suppressed the CO generation.     

Effect of catalyst preparation on Au/Ce1−xZrxO2 and Au–Cu/Ce1−xZrxO2 for steam reforming of methanol

We tested 3 wt% gold (Au) catalysts on CeO₂–ZrO₂ mixed oxides, prepared by co-precipitation (CP) and the sol–gel (SG) technique, for steam reforming of methanol (SRM). Uniform Ce_1−xZr_xO₂ solid solution was dependent on the Zr/Ce ratio, where the incorporation of Zr⁴⁺ into the Ce⁴⁺ lattice with a ratio of 0.25 resulted in smaller ceria crystallites and better reducibility, and was found to be efficient for SRM activity. The catalytic activity was suppressed when the ratio was ≥0.5, which led to the segregation of Zr from solid solution and sintering of Au nanoparticles. It was found that the CP technique produced better catalysts than SG in this case. For the bimetallic catalysts, the co-operation of Au–Cu supported on Ce_0.75Zr_0.25O₂ (CP) exhibited superior activities with complete methanol conversion and low CO concentration at 350 °C. Furthermore, the size of the alloy particle was strongly dependent on the pH level during preparation.     

管式PECVD法沉积的SiyNx/SiOxNy叠层膜的研究

本文对采用管式等离子体增强化学气相沉积(PECVD)法沉积的氮化硅与氮氧化硅(Si_yN_x/SiO_xN_y)叠层膜进行了实验研究,结果表明:在硅片正面镀膜时增加SiO_xN_y膜层,既可以增强正面的钝化效果,还可以降低对光的反射率,增加光吸收率,从而提升太阳电池的短波响应能力,通过对膜层组分和反应气体流量等工艺参数进行匹配优化,使太阳电池的光电转换效率提升了0.07%;利用Si_yN_x/SiO_xN_y叠层膜抗氧化、抗钠离子的特性,使太阳电池的抗电势诱导衰减(PID)性能提升了22%。     

Spectral Photosensitivity ofpSi—n(ZnSe)1?x?y(Si2)x(GaP)y Structures

Epitaxial layers of substitutional solid solution (ZnSe)_1−x−y(Si₂) _x (GaP) _y (0.1 ≤x≤ 1, 0≤y≤0.9) on pSi substrates were developed from a limited volume of tin solution-melt using the method of a liquid phase epitaxy. The spectral dependency of photosensitivity of the pSi—n(ZnSe)₁ −x−y (Si₂) _x (Ga.P) _y structures was studied and the peaks of photoresponses at energies of photons of 1.6, 1.66, and 1.92 eV at room temperature were discovered. It was shown that the forward-bi as regions of the volt—ampere characteristics of structures under study can be described by the power dependence of −I = I ₀ + B · V ^m with various values of a power index at various values of the voltage applied.     

Phase stability and conductivity of Ba1−ySryCe1−xYxO3−δ solid oxide fuel cell electrolyte

The structure, phase stability, and electrical properties of BaCe_1−xY_xO_3−δ (x = 0-0.4) in humidity air and CO₂ atmosphere are investigated. XRD results indicate that the BaCe_0.9Y_0.1O_3−δ sample has a symmetric cubic structure, and its phase changes to tetragonal as the Y³⁺ doping amount increases to 20 mol%. The conductivity of BaCe_1−xY_xO_3−δ increases with temperature, and it depends on the amount of yttrium doping and the atmosphere. BaCe_0.8Y_0.2O_3−δ exhibits the highest conductivity of 0.026 S cm⁻¹ at 750 °C. The activation energy for conductivity depends on yttrium doping amount and temperature. The conductivity of BaCe_0.8Y_0.2O_3−δ is 0.025 S cm⁻¹ in CO₂ atmosphere at 750 °C which is 3.8% lower than that in air due to reactions with CO₂ and BaCO₃ and the CeO₂ impure phases formed. The structure of BaCe_0.8Y_0.2O_3−δ is unstable in water and decomposes to Ba(OH)₂ and CeO₂ phases. It is found that the activation energy of samples in CO₂ atmosphere is higher than that of sample in air. Sr-doped Ba_1−ySr_yCe_0.8Y_0.2O_3−δ (y = 0-0.2) is prepared to improve the phase stability of BaCe_0.8Y_0.2O_3−δ in water. The conductivity of Ba_0.9Sr_0.1Ce_0.8Y_0.2O_3−δ is 0.023 S cm⁻¹ at 750 °C which was 11% lower than that of BaCe_0.8Y_0.2O_3−δ, however, the phase stability of Ba_0.9Sr_0.1Ce_0.8Y_0.2O_3−δ is much better than that of BaCe_0.8Y_0.2O_3−δ in water.     

Catalytic activity and characterizations of Ni/K2TixOy–Al2O3 catalyst for steam methane reforming

Nickel catalysts supported on the K₂Ti_xO_y–Al₂O₃ were prepared by the wet impregnation method for steam methane reforming to produce hydrogen. X-ray diffraction, N₂ physisorption, scanning electron microscopy with energy dispersive spectroscopy, the H₂ temperature-programed reduction technique, and X-ray photoelectron spectroscopy were employed for the characterization of catalyst samples. The results revealed that the performance of the Ni/K₂Ti_xO_y–Al₂O₃ catalysts was comparable to that of commercial FCR-4 for steam methane reforming under the mild condition. In particular, a catalytic stability test at 800 °C and in the reactant flow with the steam-to-carbon (S/C) feed ratio of 1.0 indicated that the Ni/K₂Ti_xO_y–Al₂O₃ catalysts were more active, thermally stable and resistant to deactivation than the non-promoted Ni/Al₂O₃. It is considered that the appropriate interaction strength between nickel and the modified support and proper K₂Ti_xO_y phases with a surface monolayer coverage achieved at ca. 15 wt.% loading in the support play important roles in promoting the steam methane reforming activity as well as suppressing the sintering of the catalyst.     

Planar solid-state amperometric hydrogen gas sensor based on Nafion®/Pt/nano-structured polyaniline/Au/Al2O3 electrode

The effects of Nafion^® film thickness and charges passed for the preparation of Pt and nano-structured polyaniline (nsPANi) on the sensing properties of a planar solid-state amperometric hydrogen gas sensor are investigated. The surface morphology, Pt loading and electroactive surface area (ESA) are analyzed by FESEM, inductively coupled plasma (ICP) and cyclic voltammetry (CV), respectively. The specific sensitivity of the hydrogen gas sensor can be effectively promoted by decreasing the thickness of the Nafion^® film and the charge passed for the electrodeposition of Pt and PANi (from 30 to 10 mC), respectively. The very low Pt loading of the sensing composite electrode is due to the use of the nanofibrous PANi as support, which remarkably promotes Pt utilization. The specific sensitivity and the response time of the hydrogen gas sensor based on the Nafion^® (5.7 μm)/Pt/nsPANi/Au/Al₂O₃ electrode with a Pt loading of 1.87 μg are found to be 338.50 μA ppm^?1 g^?1 and 100–250 s, respectively, for measuring 10–10,000 ppm H₂.     

Preparation and characterization of La1−xSrxNiyFe1−yO3−δ cathodes for low-temperature solid oxide fuel cells

Perovskite-type La_1−xSr_xNi_yFe_1−yO_3−δ (x = 0.3, 0.4, 0.5, 0.6, y = 0.2; x = 0.3, y = 0.2, 0.3, 0.4) oxides have been synthesized and employed as cathodes for low-temperature solid oxide fuel cells (SOFCs) with composite electrolyte. The segregation of La₂NiO_4±δ is observed to increase with the increasing Sr²⁺ incorporation content according to X-ray diffraction (XRD) results. The as-prepared powders appear porous foam-like agglomeration with particle size less than 1 μm. Maximum power densities yield as high as 725 mW cm⁻² and 671 mW cm⁻² at 600 °C for fuel cells with the LSNF4628 and LSNF7337 composite cathodes. The maximum power densities continuously increase with the increasing Sr²⁺ content in LSNF cathodes, which can be mainly ascribed to the possible charge compensating mechanism. The maximum power densities first increase with the Ni ion incorporation content up to y = 0.3 due to the increased oxygen vacancy, ionic conductivity and oxygen permeability. Further increase in Ni ion content results in a further lowering of fuel cell performance, which can be explained by the association of oxygen vacancies and divalent B-site cations in the cathode.     

Preparation and properties of BaxSr1−xCoyFe1−yO3−δ cathode material for intermediate temperature solid oxide fuel cells

Ba_xSr_1−xCo_yFe_1−yO_3−δ (BSCF) materials with perovskite structure were synthesized via solid-state reaction. Their structural characteristics, electrical-conduction behavior and cathode performance were investigated. Compared to A-site elements, B-site elements show a wide solid-solution range in BSCF. The electrical-conduction behavior of BSCF obeys the small polaron-hopping mechanism. An increase of Ba or Co content in the BSCF samples results in a decrease of electrical conductivity, which is mainly attributable to the preferential existence of B³⁺ rather than B⁴⁺ in Ba- or Co-rich samples. At the same time, this leads to increases in the lattice parameter a and the number of oxygen vacancies. BSCF samples with high Ba content show a high structural stability (high oxygen-loss temperature). Ba_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ materials present good thermal-cycling stability of the electrical conductivity. Compared with Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ, Ba_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ exhibits a better cathode performance in a Ce_0.8Gd_0.2O_2−δ (GDC)-supported half cell. The cell performance can be improved by introducing a certain amount of GDC electrolyte into the BSCF cathode material.     

Characteristics of nano La0.6Sr0.4Co0.2Fe0.8O3−δ-infiltrated La0.8Sr0.2Ga0.8Mg0.2O3−δ scaffold cathode for enhanced oxygen reduction

The chemical compatibility and electrochemical properties of nanoLa_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF)-infiltrated La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ (LSGM) scaffold were manufactured and assessed for the application as a solid oxide fuel cell cathode with an LSGM electrolyte. When the LSCF and LSGM powder mixture was fired above 950 °C, the characteristic peaks of the two materials merged and an insulation peak (derived from LaSrGaO₄) was observed. To prevent reactions between LSCF and LSGM, an infiltration technique was utilized with the LSGM as a scaffold. Using this infiltration technique, nano LSCF particles (approximately 100 nm) can be uniformly coated on the LSGM scaffold surface. Good nano particle adhesion was observed at the LSGM/LSCF interface, even at relatively low firing temperatures (850 °C). The cathode polarization resistance (R_p) of the nano LSCF infiltrated LSGM scaffold cathode was lower than that of a conventional LSCF cathode. The improvement in performance of the nano LSCF-infiltrated cathode was attributed to an increase in the number of triple phase boundaries (TPB) as a result of the nano LSCF coating. In addition, the oxygen reduction reaction (ORR) paths were extended from the TPBs to the LSCF surface because LSCF particles are considerably smaller than the LSCF oxygen ion penetration depth (3–4 μm) over the temperature range of 700 °C–800 °C.     

Cathode reaction mechanism of porous-structured Sm0.5Sr0.5CoO3−δ and Sm0.5Sr0.5CoO3−δ/Sm0.2Ce0.8O1.9 for solid oxide fuel cells

The cathode reaction mechanism of porous Sm_0.5Sr_0.5CoO_3−δ, a mixed ionic and electronic conductor (MIEC), is studied through a comparison with the composite cathode Sm_0.5Sr_0.5CoO_3−δ/Sm_0.2Ce_0.8O_1.9. First, the cathodic behaviour of porous Sm_0.5Sr_0.5CoO_3−δ and Sm_0.5Sr_0.5CoO_3−δ/Sm_0.2Ce_0.8O_1.9 are observed for micro-structure and impedance spectra according to Sm_0.2Ce_0.8O_1.9 addition, thermal cycling and long-term properties. The cathode reaction mechanism is discussed in terms of frequency response, activation energy, reaction order and electrode resistance for different oxygen partial pressures p(O₂) at various temperatures. Three elementary steps are considered to be involved in the cathodic reaction: (i) oxygen ion transfer at the cathode-electrolyte interface; (ii) oxygen ion conduction in the bulk cathode; (iii) gas phase diffusion of oxygen. A reaction model based on the empirical equivalent circuit is introduced and analyzed using the impedance spectra. The electrode resistance at high frequency (R_c,HF) in the impedance spectra represents reaction steps (i), due to its fast reaction rate. The electrode resistance at high frequency is independent of p(O₂) at a constant temperature because the semicircle of R_c,HF in the complex plane of the impedance spectra is held constant for different values of p(O₂). Reaction steps (ii) and (iii) are the dominant processes for a MIEC cathode, according to the analysis results. The proposed cathode reaction model and results for a solid oxide fuel cell (SOFC) well describe a MIEC cathode with high ionic conductivity, and assist the understanding of the MIEC cathode reaction mechanism.     

Li2CO3/Na2CO3/K2CO3及其混合熔融盐储热材料热物性分子动力学研究

对Li₂CO₃/Na₂CO₃/K₂CO₃及其二元和三元混合熔融盐的密度、比热容、黏度、热导率进行分子动力学模拟(MD),对比得出模拟结果与现有的实验数据和模拟值相近。结果表明：随着温度的升高,密度逐渐减小,离子之间的距离增加,导致对剪切应力的抵抗力变小,这说明单组分、二元和三元熔融盐黏度的负温度依赖性。对于熔融盐的热导率,单组分和二元熔融盐也呈现出负温度依赖性,而三元熔融盐趋势是随温度的升高呈上升状态。     

MnOx-CeO2/ACF型催化剂低温去除柴油机NOx研究

基于NH3-SCR低温活化反应模型,通过对催化剂表征参数和负载量进行评估分析,得出了MnOx-CeO2/ACF型催化剂低温活化和反应稳定最佳的CeO2与MnOx配比率;利用25%MnOx-5%CeO2/ACF、25%MnOx-15%CeO2/ACF、25%MnOx-25%CeO2/ACF和25%MnOx-30%CeO2/ACF共4种低温催化剂试样,在发动机排放试验台架上进行了NOx转化率、NH3存储-释放和排放测试等特性试验.结果表明,在20,～250,℃温度下,25%CeO2-25%MnOx/ACF型催化剂的NOx平均转化效率和转化波动率分别为88.7%和0.5%,验证了该催化剂低温活化和反应稳定性最好,达到了国Ⅳ排放法规催化还原柴油机NOx的限值要求.     

Synthesis and electrochemical properties of (Pr–Nd)1−ySryMnO3−δ and (Pr1−xNdx)0.7Sr0.3MnO3−δ as cathode materials for IT-SOFC

(Pr–Nd)_1−ySr_yMnO_3−δ (P-NSM, y = 0.2, 0.25, 0.3, 0.35) powders made from commercial Pr–Nd mixed oxide, as well as (Pr_1−xNd_x)_0.7Sr_0.3MnO_3−δ (PN3SM, x = 0, 0.5, 0.7, 1) were synthesized by a glycine-nitrate process and characterized as cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC). XRD patterns showed the powders had formed pure perovskite phase after being calcined at 800 °C for 2 h. (Pr–Nd)_0.7Sr_0.3MnO_3−δ (P-N3SM) achieved a high conductivity of 194 S cm⁻¹ at 500 °C and showed a good chemical stability against YSZ at 1150 °C. And the thermal expansion coefficient of P-N3SM/YSZ cathode was 11.1 × 10⁻⁶ K⁻¹, which well matched YSZ electrolyte film. The tubular SOFC with P-N3SM/YSZ cathode exhibited the maximum power densities of 415, 367, 327 and 282 mW cm⁻² at 850, 800, 750 and 700 °C, respectively, which indicated P-N3SM was potentially applied in SOFC for low cost.     

Electrical performance and structural analysis of La1−xBaxGa0.8Mg0.2O3−δ solid electrolyte

The aim of this study was to develop La_1−xBa_xGa_1−yMg_yO_3−δ (x = 0.03–0.1, y = 0.2–0.25) (LBGM) electrolytes for intermediate-temperature solid-oxide fuel cells (SOFCs); these electrolytes were synthesized via a solid-state reaction. In the study, the La_1−xBa_xGa_1−yMg_yO_3−δ samples crystallized in an orthorhombic (Imma) structure, and a BaLaGa₃O₇ phase was detected for x ≥ 0.08 at a fixed y = 0.2. The solubility limit of the Ba ions increased with an increase in the Mg content in the matrix. Two active Raman bands at ca. 677 and 739 cm⁻¹ were observed, and they were attributed to the oxygen vacancies. The La_0.95Ba_0.05Ga_0.75Mg_0.25O_3−δ sample had a higher conductivity ca. 0.1 S/cm at 800 °C, and an activation energy of ca. 0.83–1.27 eV at 500–800 °C. The thermal expansion coefficient (TEC) of the LBGM samples at 200–800 °C was in the range of 10 × 10⁻⁶ to 14 × 10⁻⁶/°C.     

Cu/MnOx–CeO2 and Ni/MnOx–CeO2 catalysts for the water–gas shift reaction: Metal–support interaction

Monometallic copper and nickel catalysts supported on cerium-manganese mixed oxides are prepared, characterized and evaluated for the Water–Gas Shift (WGS) reaction. Active metal loading of 2.5 wt% and 7.5 wt% are used to impregnate MnO_x–CeO₂ supports with 30% and 50% Mn:Ce molar ratio. The structure of the samples strongly depends on both the active metal employed and the manganese content in the mixed support. For both Cu and Ni samples, the best catalytic behavior is found in samples supported on the MnO_x–CeO₂ oxides with 30% Mn:Ce molar ratio, as a result of the presence of Cu_xMn_yO₄ spinel-type phases in the case of copper catalysts and the presence of a NiMnO₃ mixed oxide with defect ilmenite structure in the case of nickel catalysts.     

A high performance BaZr0.1Ce0.7Y0.2O3-δ-based solid oxide fuel cell with a cobalt-free Ba0.5Sr0.5FeO3-δ–Ce0.8Sm0.2O2-δ composite cathode

A cobalt-free Ba_0.5Sr_0.5FeO_3-δ–Ce_0.8Sm_0.2O_2-δ (BSF–SDC) composite is employed as a cathode for an anode-supported proton-conducting solid oxide fuel cells (H-SOFCs) using BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY) as the electrolyte. The chemical compatibility between BSF and SDC is evaluated. The XRD results show that BSF is chemically compatible with SDC after co-fired at 1000 °C for 6 h. A single cell with a 20-μm-thick BZCY electrolyte membrane exhibits excellent power densities as high as 792 and 696 mW cm⁻² at 750 and 700 °C, respectively. To the best of our knowledge, this is the highest performance reported in literature up to now for BZCY-based single cells with cobalt-free cathode materials. Extremely low polarization resistances of 0.030 and 0.044 Ωcm² are achieved at 750 and 700 °C respectively. The excellent performance implies that the cobalt-free BSF–SDC composite is a promising alternative cathode for H-SOFCs. Resistances of the tested cell are investigated under open circuit conditions at different operating temperatures by impedance spectroscopy.     

Nd0.5Sr0.5Fe0.8Cu0.2O3−δ–xSm0.2Ce0.8O1.9 cobalt-free composite cathodes for intermediate temperature solid oxide fuel cells

Cobalt-free composites Nd_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (NSFCu)–xSm_0.2Ce_0.8O_1.9 (SDC) (x = 0–60 wt%) are investigated as IT-SOFC cathodes. The characteristic properties of cobalt-free composite cathodes comparing to cobalt-based composites are revealed. The DC conductivity and thermal expansion coefficient of the composite cathodes decrease with the content of SDC x, while the polarization resistance R_p shows the least value with addition of 40 wt% of SDC. The power density of the single cell with NSFCu-40% SDC composite cathode improved significantly compared with that of undoped NSFCu cathode, with peak values of 488, 623, 849 and 1052 mW cm⁻² at 600, 650, 700, and 750 °C, respectively. Moreover, the performance of the composite cathode is stable within testing period of 370 h at 700 °C, indicating that the NSFCu-40% SDC is an excellent cobalt-free composite cathode applied in IT-SOFC.     

玻璃/ITO/pin a-Si电池研究

本文对玻璃/ITO/pin a-Si太阳电池进行了分析,研究了辉光放电等离子体对ITO的轰击作用,并讨论了制备工艺对电池特性的影响。实验发现,ITO/p~+ a-Si接触特性除上述作用的影响外,环境沾污也有重要影响。