Efficient strategy to boost the electrochemical performance of yttrium stabilized zirconia electrolyte solid oxide fuel cell for low-temperature applications

Yttrium stabilized zirconia (YSZ) used as the state-of-the-art electrolyte for solid oxide fuel cells (SOFCs) requires high temperature (over 800 °C) to realize sufficient oxygen ion conductivity. Thus, the high operational temperature is the main restriction for the commercial process of YSZ-based SOFCs. To obtain decent ionic conductivity at intermediate-low temperatures, Sr-free cathode LaNiO₃ is introduced into YSZ to construct a novel LaNiO₃-YSZ composite electrolyte, which is sandwiched by two Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) electrodes to assemble systematical fuel cells. This device presents an excellent peak output of 1045 mW cm^-2 at 600 °C and even 399 mW cm^-2 at 450 °C. A series of characterizations indicates that the oxygen ion conductivity of the LaNiO₃-YSZ composite is significantly promoted in comparison with that of pure YSZ, and the LaNiO₃ component has certain proton conductivity after hydrogenation. Both of the two factors contributes to the superior performance of such devices at intermediate-low temperatures. Furthermore, the sharp decrease in electronic conductivity for LaNiO₃ in hydrogen atmosphere combined with Schottky junction at the anode-electrolyte interface eliminates the short-circuiting problem. Our work demonstrates that incorporating Sr-free cathode LaNiO₃ into the YSZ electrolyte is an efficient strategy to boost the performance and reduce the operational temperature of YSZ-based SOFCs.     

Effect of yttrium-stabilized bismuth bilayer electrolyte thickness on the electrochemical performance of anode-supported solid oxide fuel cells

Lowering operating temperature and optimizing electrolyte thickness, while maintaining the same high efficiencies are the main considerations in fabricating solid oxide fuel cells (SOFCs). In this study, the effect of yttrium-stabilized bismuth bilayer electrolyte thickness on the electrical performance was investigated. The yttrium-stabilized bismuth bilayer electrolyte was coated on the nickel–samarium-doped composite anode/samarium-doped ceria electrolyte substrate with varying bilayer electrolyte thicknesses (1.5, 3.5, 5.5, and 7.5 μm) via dip-coating technique. Electrochemical performance analysis revealed that the bilayer electrolyte with 5.5 μm thickness exhibited high open circuit voltage, current and power densities of 1.068 V, 259.5 mA/cm² and 86 mW/cm², respectively at 600 °C. Moreover, electrochemical impedance spectroscopy analysis also exhibited low total polarization resistance (4.64 Ωcm²) at 600 °C for the single SOFC with 5.5 μm thick yttrium-stabilized bismuth bilayer electrolyte. These findings confirm that the yttrium-stabilized bismuth bilayer electrolyte contributes to oxygen reduction reaction and successfully blocks electronic conduction in Sm_0.2Ce_0.8O_1.9 electrolyte materials. This study has successfully produced an Y_0.25Bi_0.75O_1.5/Sm_0.2Ce_0.8O_1.9 bilayer system with an extremely low total polarization resistance for low-temperature SOFCs.     

Yttrium -barium oxide as a robust photocatalyst for photocatalytic degradation of organic dyes under visible light

Based on the structure related to the high-temperature superconductor yttrium-barium-copper oxide, two novel high-efficiency visible light photocatalysts were created in this study. The yttrium-barium oxide (YBO) semiconductors Y₂Ba₃O₆ (YB3O) and Y₂Ba₄O₇ (YB4O) were prepared by a copper-free solid-phase sintering method. They were applied for the effective treatment of dye-containing wastewater by photocatalysis under visible light irradiation. The degradation efficiency of methylene blue (MB) reached more than 95% within 10 min. Stable visible light degradation of methyl orange (MO) was achieved in the presence of YB3O and YB4O. The electron spin resonance technique and active substance capture technique confirmed the presence of superoxide radicals (·O₂^?), hydroxyl radicals (·OH) and holes (h_VB⁺) under visible light illumination. UV–Vis diffuse reflectance spectroscopy analysis showed that the direct optical band gaps of YB3O and YB4O were 2.550 eV and 2.583 eV, respectively, which resulted in their high visible absorption at 486.27 nm and 480.06 nm. After five cycles, the recoveries of YB3O and YB4O reached 67.15% and 72.98%. Therefore, YB3O and YB4O are considered as powerful semiconductor catalysts for the photocatalytic degradation of organic dyes in wastewater.     

Hydrogen diffusion through Ru thin films

In this paper, an experimental measurement of the diffusion constant of hydrogen in ruthenium is presented. By using a hydrogen indicative Y layer, placed under the Ru layer, the hydrogen flux through Ru was obtained by measuring the optical changes in the Y layer. We use optical transmission measurements to obtain the hydrogenation rate of Y in a temperature range from room temperature to 100 °C. We show that the measured hydrogenation rate is limited mainly by the hydrogen diffusion in Ru. These measurements were used to estimate the diffusion coefficient, D, and activation energy of hydrogen diffusion in Ru thin films to be D = 5.9 × 10⁻¹⁴ m²/s ∙ exp (-0.33 eV/k_Bτ), with k_B the Boltzmann constant and τ the temperature.     

钇与间羧基偶氮氯膦的β型显色反应研究

研究了钇与间羧基偶氮氯膦的β型显色反应和各种因素的影响，探讨了显色时间、介质酸度和试剂浓度在α－β转化反应中的作用和规律，确定了β型钇配合物的最佳形成条件和组成。发现β型显色反应存在着两种类型，并提出区别该两种类型反应的判据。     

RBS/channeling studies on the heteroepitaxially grown Y2O3 film on Si(100)

The heteroepitaxially grown yttrium oxide layer by an ionized cluster beam (ICB) on a Si(100) substrate was investigated by Rutherford backscattering spectrometry (RBS)/channeling. The channeling minimum value (χ_min) of the Y₂O₃ layer on Si(100) is 0.28, and this is the smallest value among those reported. From the channeling polar plots, it is found that Y₂O₃ film grown on Si(100) oriented with (110) direction and has a double domain structure. The 110 axis of Y₂O₃ layer is exactly parallel to the 100 axis of the Si substrate. It is also observed that the interface region of Y₂O₃ film has more crystalline defects than the surface region.     

Preparation and properties of YAG nano-sized powder from different precipitating agent

Yttrium aluminum garnet (YAG) nano-sized powder was prepared by co-precipitation method assisted by ultrasonic display using different precipitating agent. The precursor powder can crystallize into YAG phase after being calcined at 900 °C for 2 h, because of the uniformly distribution of Al and Y elements. DTA–TG and IR measurements on the precursor powder obtained were performed to improve the synthesis process. X-ray diffraction was conducted on the powder calcined at different temperatures to investigate the effect of reaction conditions on particle size and phase composition. The powder about 15 nm in diameter with pure YAG was obtained at lower temperature (900 °C) by controlling the pH value, precipitating agent and doping agent.     

Electron Microscopy of High Tc Superconductors

A review is given of structural defects occurring in different high Tc superconductors. The analysis of these defects, which is performed using electron microscopy and electron diffraction, has led in several cases to the successful synthesis of new superconducting compounds. Some of these defects also affect the superconducting properties either in a negative way (weak links) or in a positive way (flux pinning).

In this review particular attention is paid to the YBa₂Cu₃O_{7 − x} superconductor, where the detailed geometry of twin boundaries, shear planes, and dislocations is discussed together with the structural aspects of different superstructures associated with oxygen deficiency.     

Extraction and separation of yttrium from other rare earths in chloride medium by phosphorylcarboxylic acids

Two phosphorylcarboxylic acids, 3-((bis(2-ethylhexyloxy))phosphoryl)propanoic acid (PPA) and 3-((bis(2-ethylhexyloxy))phosphoryl)-3-phenylpropanoic acid (PPPA), were synthesized for separating yttrium from other rare earths in the chloride feed of ion-adsorption type rare earth concentrate. The effect of the factors such as pH_1/2, temperature, saponification degree and phase modifiers was investigated. The separation efficiencies of PPA and PPPA are obviously better than the typical extractants such as sec-octylphenoxy acetic acid (CA-12) and naphthenic acid (NA). The extraction process of rare earths by PPA and PPPA is a cation exchanging reaction, which is similar to those of CA-12 and NA. The loaded rare earths in both PPA and PPPA systems can be effectively back-extracted by 0.5 mol/L HCl or higher concentration. A cascade extraction process for separating yttrium from other rare earths was developed using PPPA as the extractant. The yttrium product with the purity of 97.20 wt% was obtained by 35 stages of extraction and 12 stages of scrubbing.