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Strontium and magnesium doped ceria solid solutions (Ce0.99Sr0.01O1.995 and Ce0.99M0.01O1.995) were synthesized by a cost effective solid state reaction. The doped and un-doped CeO2 samples were sintered at 1200 °C, 1300 °C and 1400 °C to investigate the effect of sintering temperature and doping on density, structural and morphological properties. The density was measured by Archimedes’ method. It is observed that the density increases with increasing sintering temperature and with doping of strontium. The crystal structure and surface morphology have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD and SEM reveals that the synthesized samples are single phase with a cubic fluorite structure, and the grains formed are of different sizes. The grain size depends on sintering temperature and type of doping. The lattice parameter increases with sintering temperature and substitution of Sr in ceria. The Grain size of Sr-doped ceria decreases, whereas that of Mg-doped ceria increases. EDS spectra show that the samples are free of contaminants. The Ce0.99Sr0.01O1.995 shows a more open structure than un-doped ceria. [ABSTRACT FROM AUTHOR]

Chemically stable composite BaZr0.8Y0.2O3−δ-Ni (BZY-Ni) was proposed and evaluated as the anode for solid oxide fuel cells (SOFCs) based on Ce0.8Sm0.2O2−δ (SDC) electrolyte. A thin electron-blocking interlayer was formed in situ at the anode/electrolyte interface when the anode-supported half cell was prepared via a high-temperature sintering process. Raman spectra and high-resolution TEM (HRTEM) results revealed that the electron-blocking interlayer consisted of Ce0.8Sm0.2O2−δ@Ba(Ce, Zr)1−x(Sm, Y)xO3−δ core/shell-like grains. The Ba(Ce, Zr)1−x(Sm, Y)xO3−δ shell protected SDC grains from reduction and consequently the electronic conduction through the SDC electrolyte film was nearly completely eliminated in the new structured fuel cell. The fuel cell exhibited significantly improved open circuit voltages (OCVs), high power densities as well as good operating durability, demonstrating that BZY-Ni is a promising anode for CeO2-based SOFCs operating at a higher efficiency. These findings also imply that doped CeO2@doped Ba(Ce, Zr)O3 core/shell composite is a promising electrolyte with high ionic transport number, which directs a new strategy to design novel electrolyte materials for SOFCs. [ABSTRACT FROM AUTHOR]

Solar-driven thermochemical routes enable storage of solar energy in chemical form for off-sun use by means of synthetic fuel production. Here, we explore vanadium-doped ceria materials for partial oxidation of methane, followed by an efficient splitting of CO 2 and H 2 O into syngas. The primary role of the dopant is to enhance and optimize the cycle capacity of ceria at low isothermal temperatures. The intake capacity of ceria lattice reached its saturation level with 5% of vanadium addition and further increase in V (%) forms a secondary phase (CeVO 4), which significantly affects the role of vanadium towards the syngas production performance enhancement. For instance, vanadium atoms migrate to the powder surface with V ≥ 5% and cause cracking of methane, while the lattice vanadium atoms (V < 5%) enhances the cycle capacity by providing reducing sites for the redox reactions and improve the oxygen mobility by inducing lattice distortions. The cycle capacity of V-doped ceria is four times higher than pure ceria, while the temperature for the methane partial oxidation reaction is decreased by up to 178 °C with elevated peak syngas production rates, after vanadium doping. The long-term redox activity of V-doped ceria materials for 200 cycles with up to 4.5 mmol g−1/cycle of syngas is reported. This study demonstrates the concept of utilizing V-doped ceria to produce syngas via high temperature chemical looping reforming of methane and helps to strategically evaluate the redox materials as an efficient oxygen carrier for syngas production. A mechanism of optimizing the vanadium (V5+) doping to the CeO 2 lattice. The vanadium content below 5% stays into the CeO 2 lattice, while further increase pushes the vanadium ions to the surface, chemically react with ceria and result in a segregated phase "CeVO 4 ". Vanadium ions present into the ceria lattice increase the fuel selectivity, promote reforming of methane, and enhance the H 2 purity. Whereas, vanadium contents greater than 5% causes methane cracking which result in high solid carbon contents and increase the H 2 /CO ratio during the methane partial oxidation reaction. ga1 • Fractional doping of vanadium significantly improves the syngas yields of CeO 2. • The CeO 2 lattice has capacity to incorporate upto 5% vanadium after which it forms a segregated phase of CeVO 4. • The oxygen exchange capacity of V-doped CeO 2 nanostructures is four-fold higher than pure CeO 2. • The V-doped CeO 2 nanostructures produce efficient syngas yields for up to 200 cycles. • The vanadium species are highly catalytic on the surface of CeO 2 nanopowders. [ABSTRACT FROM AUTHOR]