Fabrication and characterization of micro-tubular cathode-supported SOFC for intermediate temperature operation

We report the fabrication and characterization of a micro-tubular cathode-supported cell consisting of a Ce_0.9Gd_0.1O_1.95 electrolyte with a Ni–cermet anode on a porous La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ/Ce_0.9Gd_0.1O_1.95 (60:40 volume) tube (460 μm wall thickness and 2.26 mm diameter). The cells were fabricated by a cost-effective technique involving extrusion molding and slurry coating through a co-firing process. Densification of the ceria film (thickness < 15 μm) was successful by co-firing the laminated electrolyte with the porous cathode at 1200 °C. NiO–Ce_0.9Gd_0.1O_1.95 (Ni: Ce_0.9Gd_0.1O_1.95 = 50:50 in volume after reduction) was subsequently sintered on the electrolyte at 1100 °C to construct a 10 μm thick, porous and well-adherent anode. The cell having 1.5 cm tube length fed with humidified 30 vol.% H₂–Ar (3% H₂O) yielded the maximum power densities of 0.16, 0.13 and 0.11 W cm⁻², at 600, 550 and 500 °C, respectively. It was found that the cell performance is strongly dominated by the tube length, due to a high substrate resistance from the cathode current collections.     

Preparation and crystal structure of a new bismuth vanadate, Bi3.33(VO4)2O2

Single crystals of a new bismuth vanadate, Bi_3.33(VO₄)₂O₂ was prepared by hydrothermal reaction using a hydrated sodium bismuthate, NaBiO₃·nH₂O as one of the starting compounds. The crystal structure was determined by using single crystal X-ray diffraction data. This compound crystallizes in the triclinic space group (#2) with a = 7.114(1), b = 7.844(2), c = 9.372(2) Å, α = 106.090(7), β = 94.468(7) and γ = 112.506(8)°, Z = 2 and the final R factors are R1 = 0.052 and wR2 = 0.14 for 2085 unique reflections. The crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO₄ tetrahedra, and one of four bismuth atoms is statistically distributed in the splitting sites with the distance of 0.83 Å. This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation and its activity was less than that of monoclinic BiVO₄.     

Cobalt oxide (Co3O4) nanorings prepared from hexagonal β-Co(OH)2 nanosheets

Hexagonal cobalt hydroxide (β-Co(OH)₂) nanosheets over a size range from 100 nm to 1 μm were synthesized using a very simple hydrothermal route with cobalt naphthenate as the cobalt source. Additionally, hexagonal cobalt oxide (Co₃O₄) nanorings over a size range from 100 nm to 1 μm consisting of cubic nanocrystals were obtained via a hydrothermal method using as-prepared β-Co(OH)₂ nanosheets as the precursors. A probable mechanism of formation of the hexagonal Co₃O₄ nanorings is proposed on the basis of time-dependent experimental results.