Key Engineering Materials Vols. 512-515

Abstract: The perovskite-type Ba(Zr_0.63Ce_0.27)Y_0.1O_3-δ (BZCY) was synthesized by solid-state reaction. Sintering behavior and electrical conductivity of the electrolyte materials were improved through optimizing the content of ZnO as sintering aid. The obvious enhancement of density of sintered body was observed due to ZnO reacting with BZCY powder. Relative densities of the samples increased with ZnO content added. A conductivity of 9.27×10^-3 S/cm tested in humid hydrogen at 800°C was obtained when the ZnO content was 2 mol%. A peak power density of 12.4 mW/cm² was delivered based on a single fuel cell with electrolyte-supported configuration.

Abstract: Nano-sized electrolyte of CeO₂ doped 8YSZ with 2%mol CuO (YSZDC)powders were synthesized by solid state reaction method. Powder characteristics and electrical properties was characterized by XRD,SEM and Electrochemical workstation.The results demonstrate that the as-synthesized Y_0.08Zr_0.72Ce_0.2O_1.6 (YSZDC) and Y_0.08Zr_0.72Ce_0.18Cu _0.02O_1.6-δ(YSZDC-Cu_0.02) possessed similar powder characteristics, including cubic fluorite crystalline structure.About 150 °C reduction in densification temperature of Y_0.08Zr_0.72Ce_0.18Cu_0.02O_1.6-δ was obtained when compared with Y_0.08Zr_0.72Ce_0.2O_1.6.The YSZDC-Cu_0.02 pellets sintered at 1300 °C and the YSZDC sintered at 1450 °C exhibited relative densities of 95.66% and 94.73%,respectively.Electrolyte matrixs were prepared for electrolyte-supported SOFCs(ES-SOFC) , the suspension of NiO-YSZ anode was sprayed on the electrolyte, after co-sintering at 1300°C,electrolyte matrixs and anode were well adhered each othert, without connecting pores and cracks observed. Moerover, well electricity performance were showed by YSZDC and YSZDC-Cu_0.02 at a testing temperature of 750°C,And the electrolyte conductivity didn’t decrease obviously with dopping CuO.

Abstract: The activities of cermet catalysts composed of Ni/CeO₂-ZnO anode for steam reforming of methanol were investigated for internal reforming of solid oxide fuel cell. Ni/CeO₂-ZnO anodes with specific percentage of ceria versus zinc were fabricated by wet impregnation method. The catalysts were characterized by X-ray diffraction, Scanning electron microscope (SEM) and temperature-programmed reduction. Area specific resistance (ASR) of these anodes was also examined to prove the thermal stability of them, and possible reasons for degradation were analyzed. Furthermore, The promoting effect of zinc metals included a decrease in the reduction temperature of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of zinc metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the methanol conversions and decreasing the coke formation. The maximum power density of the single cell reached 560mW cm^-2 and 380mW cm^-2 at 750°C in hydrogen and methanol steam respectively, and the cell obtained stable output in methanol steam over an operation period of 30 h.

Abstract: The electrical resistivty (R) of BaO–CaO–SiO2–Al2O3 (BCSA) based glass, which was used in SOEC, was measured by impedance analyzer from room temperature to sealing temperature, and it was founded that electrical resistivity of all seal glass decreases with temperature. When temperature is lower than the soften temperature of glass, the electrical resistivity of all seal glass was no less than 107Ω∙cm. At 850°C, the resistivity of the 16BaO–16CaO–42SiO2–8Al2O3 glass (G1) reached 4.40×106Ω∙cm, and even at the sealing temperature, their resistivity was still above 105-106Ω∙cm. With the decrease of ratio of Si/B from 3 to 1, the electrical resistivity of glass decreased from 4.40×106Ω∙cm to 8.96×104Ω∙cm. The electrical resistivity of glass in BCSA system could be significantly affected by B2O3 and alkaline earth oxides. The results show that the electrical resistivity of glass was improved with the increasing of non-bridging oxygen and the average field strength. All glasses can be used as sealants at high temperature with no electrical shunting in SOEC.

Abstract: The physical properties and microstructures of supporting anodes are crucial for the performances of the entire SOFCs. In this investigation, the rape pollen was developed as a novel pore-former to improve the properties of the conventional NiO–YSZ(yttria-stabilized zirconia) anode substrate of solid oxide fuel cell. The advantage of using this pore-former over the conventional ones (e.g. polymethyl methacrylate (PMMA), carbon and flour) is that this pore-former had high porosity、global pore shape and uniform pore size distribution in the anode substrates, which are beneficial for rapid transport of the fuel and byproduct. The microstructure was observed by SEM, and the porosity of anode was measured by Archimedes method. The results showed that the optimum weight percent concentration was 15%, correspondingly, porosity was 40.3%, which was suitable for supporting anodes for SOFC application. And the open-circuit voltage (OCV) as high as 1.058V was obtained ,and the maximum power densities of 0.794W/cm² was achieved at 750°C, respectively, using hydrogen as fuel and ambient air as oxidant.

Abstract: Double-perovskite Sr₂Fe_1-xMn_xNbO_6-δ (x = 0, 0.1, 0.2, 0.3, 0.5, 0.8) (SFMN) powders which will be applied to the electrode of solid oxide electrolysis cells (SOEC) were synthesized by Solid State Reaction Method. The mixed oxide powders SrCO₃, Fe₂O₃, MnO₂ and Nb₂O₅, were homogeneously calcined at different temperatures and in different atmospheres. The influence of the preparation process on the structure and the morphology of the powder were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It is found that the formation of perovskite structure is directly related to the content of Mn and calcining temperature. Controllable synthesis of pure phase of double perovskite powders was realized after calcining for12h at 1150 °C in air. Moreover, the experimental results show that the perovskite structure of SFMN is stable in whether oxidizing or reducing atmosphere, which indicates that this material has a potential to be used as electrode of solid oxide electrolysis cell.

Abstract: Li₂MnSiO₄ cathode materials were prepared by hydrothermal reaction at 150°C using LiOH, Si(OC₂H₅)₄ and Mn(Ac)₂.4H₂O as raw materials followed by a low temperature heat annealing at 650°C. The samples were characterized by X-ray diffraction, scanning electron microscopy, FTIR. The powders electrochemical performance was investigated in terms of cycling behavior. Nanometer-sized flake crystalline particles of Li₂MnSiO₄ are obtained with some degree of agglomeration and little impure phases are detected after annealing. The charge capacity of the Li₂MnSiO₄ samples is 306 mAh/g (about 1.84 Li⁺ per unit formula extracted), and the discharge capacity is 114 mAh/g (about 0.68 Li⁺ per unit formula inserted) in the first cycle in the voltage range of 1.5–4.8 V under a rate of C⁄20. With increasing cycle number, the cell exhibits a well cycle performance with more than 95% coulombic efficiency and the maintenance of 61% of its discharge capacity after 50 cycles.

Abstract: Mixtures of TiO₂•0.2H₂O (HTO) and LiFePO₄ were prepared via three main composite methods: 2-2 series model, 2-2 parallel model and 3-3 model. HTO had been reported to exhibit high specific capacity (~200 mAh/g at 1 C) as well as excellent cycle property, whereas its voltage plateau was too low (about 1.7 V vs. Li) as a cathode material. LiFePO₄ was a promising cathode material for its high voltage plateau (about 3.4 V vs. Li), low cost and high specific capacity (~150 mAh/g at 1 C). However, because of its low conductivity, the rate property as well as cycle property was limited. The mixtures of HTO and LiFePO4 were considered to combine the advantages of both materials. By comparison, the 2-2 parallel model excelled in both rate property and cycle property. Its specific capacity can reach as high as 220 mAh/g with a high specific energy of 450 Wh/Kg at 0.1 C. Even after cycled 200 times at 2 C, the capacity can still be higher than 100 mAh/g. CV measurements and a combined constant current and constant voltage tests supported a two plateaus process for 2-2 parallel model. The charge-discharge voltage gap increased for the 2-2 parallel composites, which was supposed to be related to the interface. In general, the specific energy was much higher than HTO while the specific capacity as well as cycle property was much better than LiFePO₄ as a cathode material. .

Abstract: Single-crystal TiO₂ nanorod film was synthesized directly on FTO substrates with various lengths by changing the hydrothermal growth parameters including growth time and growth temperature. The obtained nanorod arrays were incorporated in organic solar cells as buffer layer instead of PEDOT: PSS. Results showed that devices assembled with TiO₂ nanorods film of 200 nm in length exhibited a lower open-circuit voltage but a significantly higher short-circuit current density compared to those of normal FTO/PEDOT: PSS/P3HT: PCBM/Al structure with a comparable active layer thickness. Overall the power conversion efficiency was boosted by two-fold. Electrochemical impedance spectroscopy (EIS) analyses revealed that the improvement in the photovoltaic performance was induced by the inhibited recombination and consequently enhanced electron lifetime.

Abstract: Electrochromism have been widely investigated due to their potential applications such as automobile and building window. In this study, tantalum oxide thin films used as ion conducting layer were deposited on WO₃/ITO at room temperature by magnetron sputtering. The thickness of tantalum oxide films were varied to investigate their effects on composition, microstructure, optical properties, and electrochromic properties determined by X-ray diffraction, UV-visible spectrometer, Atomic force microscope (AFM), and field-emission scanning electron microscope (FE-SEM). Experimental results indicated Ta₂O₅ at thickness of 300 nm with low packing density were favorable for ions transmission deposited on WO₃/ITO had better electrochromic property.