Co/Fe oxide and Ce0.8Gd0.2O2-delta composite interlayer for solid oxide electrolysis cell

A composite interlayer comprised of gadolinia doped ceria (GDC) and Co/Fe oxide was prepared and investigated for solid oxide electrolysis cell with yttrium stabilized zirconia (YSZ) electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-delta(LSCF) anode. The interlayer was constructed of a base layer of GDC and a top layer of discrete Co3O4/FeCo2O4 particles. The presence of the GDC layer drastically alleviated the undesired reactions between LSCF and YSZ, and the presence of Co/Fe oxide led to further performance improvement. At 800 degrees C and 45% humidity, the cell with 70% Co/Fe-GDC interlayer achieved 0.98 A/cm(2) at 1.18 V, 14% higher than the cell without Co/Fe oxide. Electrochemical impedance spectroscopy (EIS) revealed that with higher Co/Fe content, both the ohmic resistance and the polarization resistance of the cell were reduced. It is suggested that Co/Fe oxide can react with the Sr species segregated from LSCF and Sr1-x(Co,Fe)O3-delta, a compound with high catalytic activity and electronic conductivity. The Sr-capturing ability of Co/Fe oxide in combination with the Sr-blocking ability of GDC layer can effectively suppress the undesired reaction between LSCF and YSZ, and consequently improve the cell performance. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved

Co-synthesized Y-stabilized Bi2O3 and Sr-substituted LaMnO3 composite anode for high performance solid oxide electrolysis cell

In this study we report a nano-composite anode comprised of Y-stabilized Bi2O3 (YSB) and Sr-substituted LaMnO3 (LSM) for solid oxide electrolysis cell (SOEC). The composite powder with primary particle size ranging from 20 to 80 nm is co-synthesized via a simple citric-nitrate combustion method. X-ray diffraction examination confirms cubic fluorite YSB and rhombohedral perovskite LSM as the main phases in the composite. Temperature programmed O-2 desorption identifies remarkable low temperature desorption at 330 degrees C. Similarly, temperature programmed H-2 reduction reveals strong reduction at 385 degrees C. The facile oxygen evolution on YSB-LSM may result from the increased amount of oxygen vacancies and improved oxygen ion mobility. A cell employing YSB-LSM composite anode achieves current density of -1.52 A cm(-2) at 800 degrees C and 1.28 V, 50% higher than conventional LSM-YSZ cell. Impedance results and analysis of distribution of relaxation times indicate that the rate-determining anode processes are effectively accelerated on YSB-LSM. The activation energy for oxygen evolution reaction on YSB-LSM is reduced to 0.65 eV, notably lower than on LSM-YSZ (1.29 eV). The high performance of YSB-LSM composite anode is attributed to the fast ion decorporation on YSB, the facile O-2 formation on LSM, and the abundant phase boundaries that facilitate the two processes. (C) 2016 Elsevier B.V. All rights reserved

Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported. (C) 2016 Elsevier B.V. All rights reserved

Ordered structures of defect clusters in gadolinium-doped ceria

The nano-domain, with short-range ordered structure, has been widely observed in rare-earth-doped ceria. Atomistic simulation has been employed to investigate the ordering structure of the nanodomain, as a result of aggregation and segregation of dopant cations and the associated oxygen vacancies in gadolinium-doped ceria. It is found that the binding energy of defect cluster increases as a function of cluster size, which provides the intrinsic driving force for the defect cluster growth. However, the ordered structures of the defect clusters are different from the chain model as previously reported. Adjacent oxygen vacancies prefer to locate along 110/2 lattice vector, which results in a unique stable structure (isosceles triangle) formation. Such isosceles triangle structure can act as the smallest unit of cluster growth to form a symmetric dumbbell structure. This unique dumbbell structure is hence considered as a building block for the development of larger defect clusters, leading to nano-domain formation in rare-earth-doped ceria

Electrochemical behaviors of infiltrated (La, Sr) MnO3 and Y2O3-ZrO2 nanocomposite layer

(La0.8Sr0.2)(0.9)MnO3-delta-Y0.15Zr0.85O1.93 (LSM-YSZ) nanocomposite layer is infiltrated into three different scaffolds of ion-conductive YSZ, ionic and electronic conductive LSM-YSZ composite and insulating Al2O3 and used as cathode for anode supported cells. The cell performance and impedance spectra analysis reveal that the LSM-YSZ nanocomposite layer shows considerable high ORR activity using its own electronic and ionic conducting network, however, the electrochemical performance seems to be constrained by its limited ionic and electronic conductivity. The construction of ionic conducting path using YSZ scaffold is more effective for raising electrochemical performance than the construction of both electronic and ionic conducting paths using LSM-YSZ composite scaffold. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

LSM-YSZ nano-composite cathode with YSZ interlayer for solid oxide fuel cells

Low temperature prepared (La-0.8 Sr-0.2)(0.9) MnO3-delta-Y-0.15 Zr-0.85 O-1.93 (LSM-YSZ) nano-composite cathode has high three-phase boundary (TPB) density and shows higher oxygen reduction reaction (ORR) activity than traditional LSM-YSZ cathode at reduced temperatures. But the weak connection between cathode and electrolyte due to low sintering temperature restrains the performance of LSM-YSZ nano-composite cathode. A YSZ interlayer, consisted of nanoparticles smaller than 10 nm, is introduced by spinning coating hydrolyzed YSZ sol solution on electrolyte and sintering at 800 degrees C. The thickness of the interlayer is about 150 nm. The YSZ interlayer intimately adheres to the electrolyte and shows obvious agglomeration with LSM-YSZ nano-composite cathode. The power densities of the cell with interlayer are 0.83, 0.46 and 0.21 W/cm 2 under 0.7 V at 80 0, 70 0 and 600 degrees C, respectively, which are 36%, 48% and 50% improved than that of original cell. The interlayer introduction slightly increases the ohmic resistance but significantly decreases the polarization resistance. The depressed high frequency arcs of impedance spectra suggest that the oxygen incorporation kinetics are enhanced at the boundary of YSZ interlayer and LSM-YSZ nanocomposite cathode, contributing to improved electrochemical performance of the cell with interlayer. (C) 2016Science Press and Dalian Institute of Chemical Physics,Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved

Highly Active Ag-TiO2 Nanocomposite from Atom Deposition in Ethylenediamine-Complexing Silver Mirror Reaction

Ag-TiO2 nanocomposite consisting of Ag clusters on the surface of TiO2 nanocrystals has been prepared by an ethylenediamine-complexing silver mirror reaction, which employs ethylenediamine (C2H8N2) rather than ammonia as a complexing agent. In this synthesis, the reduction reaction is finely tuned by varying the C2H8N2/H2O volume ratio. With the C2H8N2/H2O volume ratio at 1:4, the reduction can proceed in a more controllable manner, and the emerging Ag atoms in solution directly deposit on TiO2 nanocrystal surfaces, while self-nucleation and growth of nuclei to large size of free-standing Ag nanoparticles cannot occur. The obtained Ag-TiO2 nanocomposite shows excellent catalytic activity for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4

Size-controlled synthesis of silver nanoparticles from silver mirror reaction in toluene

Size-controlled silver nanoparticles (Ag NPs) with a size of 2-15 nm have been synthesised from silver (Ag) mirror reaction in toluene , which refers to reduction of Ag precursor (Ag-dodecylamine complexes solution) by acetaldehyde (CH3CHO) in the presence of oleic acid (OLA). In this synthesis, the size of Ag NPs was finely tuned by just varying the Ag precursor concentrations (c(Ag)). The addition of OLA can play an important role in stabilising the emerging Ag nuclei. With the OLA/Ag molar ratio at 3:1, the adsorption layer of enough OLA on the surface of the emerging Ag nuclei prevented the direct contact between Ag+ ions and Ag nuclei, and Ag nuclei grew up to their final size by the aggregation mechanism

Tuned depositing Ag clusters on ZrO2 nanocrystals from silver mirror reaction of silver-dodecylamine complexes

We for the first time have synthesized Ag/ZrO2 nanocomposites from silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde (CH3CHO) in the presence of ZrO2 nanocrystals. The obtained nanocomposites show excellent catalytic activity in the successive reduction of p-nitrophenol (4-NP) by NaBH4

A ternary cathode composed of LSM, YSZ and Ce0.9Mn0.1O2-delta for the intermediate temperature solid oxide fuel cells

The YSZ electrolyte fuel cell with a ternary cathode composed of LSM-YSZ-Ce0.9Mn0.1O2-delta exhibits ca. 2.6 times higher current density than that with a binary cathode composed of LSM-YSZ at 600 degrees C