Lanthanum Ferrites-Based Exsolved Perovskites as Fuel-Flexible Anode for Solid Oxide Fuel Cells

Cobalt oxide enhanced lanthanum strontium cobalt ferrite electrode for solid oxide fuel cells

A Co3O4 enhanced La0.8Sr0.2Co0.5Fe0.5O3 - δ (LSCF) electrode is developed for use in air electrodes with proton conducting solid oxide fuel cell (SOFC). The incipient wetness impregnation method enables Co3O4 nanoparticles on the LSCF surface without altering the bulk porosity of the LSCF electrode. The polarization resistance of LSCF electrodes is significantly reduced by Co3O4 doping, and both charge transfer and diffusion/conversion resistances were positively affected. The highest reduction in charge transfer resistance is obtained at 700 °C, which is increased from 21%to 32%through reduction of po 2. Conversely, the highest reduction in diffusion/conversion resistance is achieved at 550 °C. By increasing po 2, the reduction is increased from 57%to 66%and its activation energy is reduced up to 33 %compared to pure LSCF. The lowest total area specific resistances obtained under air are 1.45 Ω·cm2, 2.95 Ω·cm2, 6.75 Ω·cm2 and 16.45 Ω·cm2 at 700 °C, 650 °C, 600 °C and 550 °C, respectively.

Undoped Sr2MMoO6 Double Perovskite Molybdates (M = Ni, Mg, Fe) as Promising Anode Materials for Solid Oxide Fuel Cells

The chemical design of new functional materials for solid oxide fuel cells (SOFCs) is of great interest as a means for overcoming the disadvantages of traditional materials. Redox stability, carbon deposition and sulfur poisoning of the anodes are positioned as the main processes that result in the degradation of SOFC performance. In this regard, double perovskite molybdates are possible alternatives to conventional Ni-based cermets. The present review provides the fundamental properties of four members: Sr₂NiMoO_6-δ, Sr₂MgMoO_6-δ, Sr₂FeMoO_6-δ and Sr₂Fe_1.5Mo_0.5O_6-δ. These properties vary greatly depending on the type and concentration of the 3d-element occupying the B-position of A₂BB’O₆. The main emphasis is devoted to: (i) the synthesis features of undoped double molybdates, (ii) their electrical conductivity and thermal behaviors in both oxidizing and reducing atmospheres, as well as (iii) their chemical compatibility with respect to other functional SOFC materials and components of gas atmospheres. The information provided can serve as the basis for the design of efficient fuel electrodes prepared from complex oxides with layered structures.

Minerals in biology and medicine

Natural minerals ('stone drugs') have been used in traditional Chinese medicines for over 2000 years, but there is potential for modern-day use of inorganic minerals to combat viral infections, antimicrobial resistance, and for other areas in need of new therapies and diagnostic aids. Metal and mineral surfaces on scales from milli-to nanometres, either natural or synthetic, are patterned or can be modified with hydrophilic/hydrophobic and ionic/covalent target-recognition sites. They introduce new strategies for medical applications. Such surfaces have novel properties compared to single metal centres. Moreover, 3D mineral particles (including hybrid organo-minerals) can have reactive cavities, and some minerals have dynamic movement of metal ions, anions, and other molecules within their structures. Minerals have a unique ability to interact with viruses, microbes and macro-biomolecules through multipoint ionic and/or non-covalent contacts, with potential for novel applications in therapy and biotechnology. Investigations of mineral deposits in biology, with their often inherent heterogeneity and tendency to become chemically-modified on isolation, are highly challenging, but new methods for their study, including in intact tissues, hold promise for future advances.

The Effect of Ni-Modified LSFCO Promoting Layer on the Gas Produced through Co-Electrolysis of CO2 and H2O at Intermediate Temperatures

The co-electrolysis of CO2 and H2O at an intermediate temperature is a viable approach for the power-to-gas conversion that deserves further investigation, considering the need for green energy storage. The commercial solid oxide electrolyser is a promising device, but it is still facing issues concerning the high operating temperatures and the improvement of gas value. In this paper we reported the recent findings of a simple approach that we have suggested for solid oxide cells, consisting of the addition of a functional layer coated to the fuel electrode of commercial electrochemical cells. This approach simplifies the transition to the next generation of cells manufactured with the most promising materials currently developed, and improves the gas value in the outlet stream of the cell. Here, the material in use as a coating layer consists of a Ni-modified La0.6Sr0.4Fe0.8Co0.2O3, which was developed and demonstrated as a promising fuel electrode for solid oxide fuel cells. The results discussed in this paper prove the positive role of Ni-modified perovskite as a coating layer for the cathode, since an improvement of about twofold was obtained as regards the quality of gas produced.

Topotactic Oxidation of Perovskites to Novel SrMo1-xMxO4-δ (M = Fe and Cr) Deficient Scheelite-Type Oxides

New polycrystalline SrMo_1−xM_xO_4−δ (M = Fe and Cr) scheelite oxides have been prepared by topotactical oxidation, by annealing in air at 500 °C, from precursor perovskites with the stoichiometry SrMo_1−xM_xO_3−δ (M = Fe and Cr). An excellent reversibility between the oxidized Sr(Mo,M)O_4−δ scheelite and the reduced Sr(Mo,M)O_3−δ perovskite phase accounts for the excellent behavior of the latter as anode material in solid-oxide fuel cells. A characterization by X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) has been carried out to determine the crystal structure features. The scheelite oxides are tetragonal, space group I4₁/a (No. 88). The Rietveld-refinement from NPD data at room temperature shows evidence of oxygen vacancies in the structure, due to the introduction of Fe³⁺/Cr⁴⁺ cations in the tetrahedrally-coordinated B sublattice, where Mo is hexavalent. A thermal analysis of the reduced perovskite (SrMo_1−xM_xO_3−δ) in oxidizing conditions confirms the oxygen stoichiometry obtained by NPD data; the stability range of the doped oxides, below 400–450 °C, is lower than that for the parent SrMoO₃ oxide. The presence of a Mo⁴⁺/Mo⁵⁺ mixed valence in the reduced SrMo_1−xM_xO_3−δ perovskite oxides confers greater instability against oxidation compared with the parent oxide. Finally, an XPS study confirms the surface oxidation states of Mo, Fe, and Cr in the oxidized samples SrMo_0.9Fe_0.1O_4-δ and SrMo_0.8Cr_0.2O_4-δ.