Modified strontium titanates have received much attention recently for their potential as anode material in solid oxide fuel cells (SOFC). Their inherent redox stability and superior tolerance to sulphur poisoning and coking as compared to Ni based cermet anodes could improve durability of SOFC systems dramatically.Various substitution strategies can be deployed to optimise materials properties in these strontium titanates, such as electronic conductivity, electrocatalytic activity, chemical stability and sinterability, and thus mechanical strength. Substitution strategies not only cover choice and amount of substituent, but also perovskite defect chemistry, distinguishing between A-site deficiency (A 1Àx BO 3 ) and cationstoichiometry (ABO 3+d ). Literature suggests distinct differences in the materials properties between the latter two compositional approaches. After discussing the defect chemistry of modified strontium titanates, this paper reviews three different A-site deficient donor (La, Y, Nb) substituted strontium titanates for their electrical behaviour and fuel cell performance. Promising performances in both electrolyte as well as anode supported cell designs have been obtained, when using hydrogen as fuel.Performances are retained after numerous redox cycles. Long term stability in sulphur and carbon containing fuels still needs to be explored in greater detail.

Novel molybdate materials with varying Mo valence were synthesized as possible negative-electrode materials for solid oxide cells. The phase, stability, microstructure and electrical conductivity were characterized. The electrochemical activity for H 2 O and CO 2 reduction and H 2 and CO oxidation was studied using simplified geometry point-contact electrodes. Unique phenomena were observed for some of the materials -they decomposed into multiple phases and formed a nanostructured surface upon exposure to operating conditions (in certain reducing atmospheres). The new phases and surface features enhanced the electrocatalytic activity and electronic conductivity. The polarization resistances of the best molybdates were two orders of magnitude lower than that of donor-doped strontium titanates. Many of the molybdate materials were significantly activated by cathodic polarization, and they exhibited higher performance for cathodic (electrolysis) polarization than for anodic (fuel cell) polarization, which makes them especially interesting for use in electrolysis electrodes.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract

No abstract

Electrolyte supported cells (ESC), with Sc2O3‐stabilized ZrO2 (ScSZ) electrolytes, Gd‐doped ceria (CGO) or M/CGO (M = Ni, Ru) infiltrated Sr0.94Ti0.9Nb0.1O3 (STN94) anodes and LSM/YSZ cathodes, were evaluated for their initial performance and long‐term stability. Power density for the Ru/CGO infiltrated cell reached ∼0.7 W cm–2 at 850 °C, 4% H2O/H2, whereas the Ni/CGO infiltrated cell reached ∼0.3 W cm–2, with the current morphologies and loadings. Operation at 0.125 A cm–2, 850 °C, feeding 50% H2O/H2 to the anode and air to the cathode, for a period >300 h, showed superior stability for the Ru/CGO infiltrated cell, with ∼0.04 mV h–1 degradation rate, when compared to the Ni/CGO infiltrated cell (∼0.5 mV h–1). For the Ni/CGO case, the observed degradation has been tentatively linked to initial changes in the electrochemical active area and long‐term detrimental interactions between components.

The concept of using electronically conducting anode backbones with subsequent infiltration of electrocatalytic active materials has been used to develop an alternative solid oxide fuel cell (SOFC) design based on a ferritic stainless steel support. The anode backbone consists of a composite made of Nb‐doped SrTiO3 (STN) and FeCr stainless steel. A number of different experimental routes and analysis techniques have been used to evaluate the microstructural and chemical changes occurring in the composite anode layer during electrochemical testing at intermediate temperatures (650 °C). STN and FeCr stainless steel was found to be compatible on the macro‐scale level, however, some micro‐scale chemical interaction was observed. The composite anode backbone showed a promising corrosion resistance, with a decrease in formation of Cr2O3 on the FeCr particles, when exposed to SOFC operating conditions. The electronic conductivity of the infiltrated anode backbone furthermore showed good redox stability properties. Electrochemical testing of metal‐supported cells having the STN:FeCr composite anode backbone infiltrated with electrocatalysts showed comparable performance and promising durability properties compared with other metal‐supported cell designs presented in the literature. This work illustrates the potential advantages and challenges when incorporating SrTiO3‐based materials into metal‐supported cells based on ferritic stainless steel.

Sun, X.; Sudireddy, B. R.; Tong, X.; Chen, M.; Brodersen, K.; Hauch, A.Reversible solid oxide cells (rSOCs) hold a considerable potential to play a very important role in the future energy system. The present work focuses on understanding the effect of initial cell performance, duration of the operation when cycling between SOFC and SOEC modes, current density and temperature on the durability of rSOCs. Two different cell designs are developed and their performance in reversible operation was evaluated. Type I is Ni-yttria stabilized zirconia (Ni-YSZ) fuel electrode supported planar SOCs, with a LSC-CGO (La 0.6 Sr 0.4 CoO 3-δ -Ce 0.9 Gd 0.1 O 2-δ ) composite oxygen electrode, Type II is the same fuel-electrode supported half-cell with CGO oxygen electrode backbone infiltrated with LSC nano-electrocatalysts. Comparable degradation rates of below 5-10%/1000 hours were achieved for Type I cells operated at ±0.5 A/cm 2 , or for Type II cells operated at ±1.25 A/cm 2 . The electrochemical performance and durability of both cell types are compared and the observed degradation behavior is discussed. , 91 (1) 2631-2639 (2019) ECS Transactions 2631) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 192.38.90.17 Downloaded on 2019-09-04 to IP