The role of defect chemistry in strontium titanates utilised for high temperature steam electrolysis

Tsekouras, George; Irvine, John T. S.

doi:10.1039/c1jm11313e

Cited by 88 publications

(58 citation statements)

References 38 publications

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“…If strontium ions in SrTiO 3 migrate towards the surface forming different phases, it is evident that the corresponding vacancies are left behind (see ESR analysis above) and the perovskite lattice can be considered as A‐site deficient. A‐site deficiency promotes the oxygen exchange kinetics and therefore has beneficial effect for the catalytic properties of perovskite oxides . In particular, improved catalytic activity has been recently shown when highly oxidative oxygen (O 2 2− /O − ) is present in A‐site deficient perovskites, as a result of surface oxygen vacancies .…”

Section: Resultsmentioning

confidence: 99%

Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields

et al. 2019

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In the present work the effect of electric field assisted treatments, i. e. flash sintering, on the physicochemical properties and surface reactivity of SrTiO3 nanoparticles is investigated. The materials were prepared by a hydrothermal approach and consolidated at high temperatures by conventional and electric field assisted procedures. The exposure to an electric field from 300 to 900 V/cm allowed rapid consolidation with progressive reduction of the grain growth and the shrinkage of the specific surface area to 22% and 43%, respectively. XPS analyses evidenced increasing Sr segregation at the surface if voltage was applied during the treatment. The corresponding presence of Sr vacancies in the perovskite lattice was demonstrated by ESR spectroscopy. Both techniques pointed out the appearance of highly oxidative O− species in all ceramics. The materials reactivity was investigated by methane oxidation, chosen as model high temperature catalytic reaction. With respect to conventionally treated SrTiO3, the surface area normalized reaction rate significantly improved for the ceramics exposed to electric field, until a maximum of three times for the material treated at 900 V/cm. Such enhanced properties were ascribed to the larger extent of Sr enrichment and in particular to the correlated field‐induced defect structure perturbation.

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Section: Resultsmentioning

confidence: 99%

Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields

et al. 2019

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“…Operation at high temperature (500-1000 o C) reduces the electrical energy requirement for the electrolysis and also increases the thermal efficiency of the power-generating cycle [2][3][4] . The lack of synchronization between the electricity production and consumption makes energy storage crucial for the grid to function effectively.…”

Section: Introductionmentioning

confidence: 99%

Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell

Irvine

2015

Faraday Discuss.

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For an efficient high-temperature reversible solid oxide fuel cell (RSOFC), the oxygen electrode should be highly active for the conversion between oxygen anions and oxygen gas. CaMnO(3-δ) (CM) is a perovskite that can be readily reduced with the formation of Mn(3+) giving rise to oxygen defective phases. CM is examined here as the oxygen electrode for a RSOFC. CaMn(0.9)Nb(0.1)O(3-δ) (CMN) with Nb doping shows superior electric conductivity (125 S cm(-1) at 700 °C) compared with CM (1-5 S cm(-1) at 700 °C) in air which is also examined for comparison. X-ray diffraction (XRD) data show that CM and CMN are compatible with the widely used yttria-stabilized zirconia (YSZ) electrolyte up to 950 °C. Both materials show a thermal expansion coefficient (TEC) close to 10.8-10.9 ppm K(-1) in the temperature range between 100-750 °C, compatible with that of YSZ. Polarization curves and electrochemical impedance spectra for both fuel cell and steam electrolysis modes were investigated at 700 °C, showing that CM presented a polarization resistance of 0.059 Ω cm(2) under a cathodic bias of -0.4 V while CMN gave a polarization resistance of 0.081 Ω cm(2) under an anodic bias of 0.4 V. The phase stability up to 900 °C of these materials was investigated with thermogravimetric analysis (TGA) and variable temperature XRD.

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“…[1][2][3][4][5] Natural gas reforming is currently a main way for massive hydrogen production, but still relies on fossil fuel consumption. 6 Water electrolysis capable of producing hydrogen is still far away to its real application because of the huge electricity consumption for water splitting.…”

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Composite Oxygen Electrode Based on LSCM for Steam Electrolysis in a Proton Conducting Solid Oxide Electrolyzer

Gan

Zhang

et al. 2012

J. Electrochem. Soc.

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This paper presents a ceramic composite oxygen electrode (La 0.75 Sr 0.25 ) 0.95 Mn 0.5 Cr 0.5 O 3-δ (LSCM) -BaCe 0.5 Zr 0.3 Y 0.16 Zn 0.04 O 3-δ (BCZYZ) for steam electrolysis in a proton-conducting Solid Oxide Electrolyzer (SOE) with proton conducting electrolyte BCZYZ and fuel electrode BCZYZ/Ni at 700 • C. AC impedance spectroscopy and I-V tests demonstrate two main processes from 0 to 2 V with 3%H 2 O/N 2 vs 5% H 2 /Ar: reoxidation of the LSCM electrode below 1.2 V and oxidation of H 2 O above 1.2 V. The current density reaches 2 Acm −2 at 2 V with electrode polarization of 0.1 cm 2 and steam electrolysis shows short term stability with current efficiency of 22%.Hydrogen is regarded as the leading candidate fuel because it has the potential to address the environmental and energy security issues associated with fossil hydrocarbon fuels. 1-5 Natural gas reforming is currently a main way for massive hydrogen production, but still relies on fossil fuel consumption. 6 Water electrolysis capable of producing hydrogen is still far away to its real application because of the huge electricity consumption for water splitting. 7 On the contrary, steam electrolysis is more promising as the high temperature heat partly offers the energy for steam dissociation and then leads to favorable kinetics and thermodynamics. [8][9][10][11] Proton conducting solid oxide electrolysis cells (SOECs) as the reverse mode of proton conducting Solid Oxide Fuel Cells (SOFCs) have attracted considerable attention because they are able to operate in high efficiency in conjunction with renewable electricity and to effectively exploit available heat streams (such as exhaust heat from nuclear plant). 12-15 They can efficiently produce pure hydrogen through high-temperature steam electrolysis. In this process, steam is oxidized in the oxygen electrode and simultaneously split into oxygen and proton under external electrolysis potential. Protons diffuse across the proton conducting electrolyte to the fuel electrode where the formation of pure hydrogen from protons takes place in the three-phase boundary. The formation of hydrogen only takes place in fuel electrode compartment, which makes it unnecessary to separate hydrogen from steam.The oxygen electrode is under strongly oxidizing condition in steam electrolysis, which hence a pure redox active metal is not able to work. It is therefore necessary to develop an appropriate oxygen electrode with high catalytic activity and low over potentials. The perovskite (La 0.75 Sr 0.25 ) 0.95 Mn 0.5 Cr 0.5 O 3-δ (LSCM) is an active and redox stable material which has attracted a lot of attention in SOFCs 16-24 and can hereby be considered as a good oxygen electrode material candidate. High-performance Pervoskite-type ceramic BaCe 0.5 Zr 0.3 Y 0.16 Zn 0.04 O 3-δ (BCZYZ) is adopted as electrolyte in this work because it has been recently proven to be an excellent proton conductor with good chemical stability, high proton conductivity as well as low sintering temperature. 25 In this work, a composite oxygen e...

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The role of defect chemistry in strontium titanates utilised for high temperature steam electrolysis

Cited by 88 publications

References 38 publications

Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields

Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields

Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell

Composite Oxygen Electrode Based on LSCM for Steam Electrolysis in a Proton Conducting Solid Oxide Electrolyzer

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The role of defect chemistry in strontium titanates utilised for high temperature steam electrolysis

Cited by 88 publications

References 38 publications

Enhancement of the SrTiO3 Surface Reactivity by Exposure to Electric Fields

Enhancement of the SrTiO3 Surface Reactivity by Exposure to Electric Fields

Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell

Composite Oxygen Electrode Based on LSCM for Steam Electrolysis in a Proton Conducting Solid Oxide Electrolyzer

Contact Info

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Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields

Enhancement of the SrTiO₃ Surface Reactivity by Exposure to Electric Fields