Enhanced reducibility and conductivity of Na/K-doped SrTi0.8Nb0.2O3

Xiao, Guoliang; Nuansaeng, Sirikanda; Zhang, Lei; Suthirakun, Suwit; Heyden, Andreas; Loye, Hans-Conrad zur; Chen, Fanglin

doi:10.1039/c3ta11631j

Cited by 22 publications

(15 citation statements)

References 25 publications

(35 reference statements)

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“…Appropriate amounts of SrCO 3 , TiO 2 and Nb 2 O 5 powders were mixed together and ball-milled for 15 min in acetone. The dried powders were pressed into pellets and fired at 1300°C for 10 h in air2627. Sr 0.95 Ti 0.8 Nb 0.1 Mn 0.1 O 3 (STNMO) and Sr 0.95 Ti 0.8 Nb 0.1 Cr 0.1 O 3.00 (STNCO) powders were similarly prepared using the method described above.…”

Section: Methodsmentioning

confidence: 99%

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

Zhang

Xie

Wei

et al. 2014

Sci Rep

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In this work, redox-active Mn or Cr is introduced to the B site of redox stable perovskite Sr0.95Ti0.9Nb0.1O3.00 to create oxygen vacancies in situ after reduction for high-temperature CO2 electrolysis. Combined analysis using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis confirms the change of the chemical formula from oxidized Sr0.95Ti0.9Nb0.1O3.00 to reduced Sr0.95Ti0.9Nb0.1O2.90 for the bare sample. By contrast, a significant concentration of oxygen vacancy is additionally formed in situ for Mn- or Cr-doped samples by reducing the oxidized Sr0.95Ti0.8Nb0.1M0.1O3.00 (M = Mn, Cr) to Sr0.95Ti0.8Nb0.1M0.1O2.85. The ionic conductivities of the Mn- and Cr-doped titanate improve by approximately 2 times higher than bare titanate in an oxidizing atmosphere and 3–6 times higher in a reducing atmosphere at intermediate temperatures. A remarkable chemical accommodation of CO2 molecules is achieved on the surface of the reduced and doped titanate, and the chemical desorption temperature reaches a common carbonate decomposition temperature. The electrical properties of the cathode materials are investigated and correlated with the electrochemical performance of the composite electrodes. Direct CO2 electrolysis at composite cathodes is investigated in solid-oxide electrolyzers. The electrode polarizations and current efficiencies are observed to be significantly improved with the Mn- or Cr-doped titanate cathodes.

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Section: Methodsmentioning

confidence: 99%

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

Zhang

Xie

Wei

et al. 2014

Sci Rep

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“…5 is that K-doped CuO films have consistently higher conductivity than Na-doped CuO films for the same doping concentration. It is known that the lattice parameter is dependent on the atomic radii of the dopant and the doped material [35]. In our case, atomic radius difference between K and Cu (243 -157 pm = 86) is bigger than Na and Cu (190 -157 = 33).…”

Section: Electrical Characterizationmentioning

confidence: 54%

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

Şahin

Kaya

2016

Applied Surface Science

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In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Currentvoltage (I-V) measurements. Structural properties of the CuO films were affected from doping.The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases.Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4M % doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4M % Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.

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“…However, the high cost of cobalt, mismatched thermal expansion coefficients (TECs) with ceria-based electrolytes, and chemical incompatibility with zirconium-based electrolytes are the major concerns for the practical application of cobalt-containing perovskites in IT-SOFCs. [26][27][28][29] In our recent work, a synergistic effect was observed from both the doped monovalent Li or K ions and the A-site deficiency, which bestows the pristine SrFe 0.8 Nb 0.1 Ta 0.1 O 3-δ perovskite with a remarkably high ORR activity even comparable to the benchmark cobalt-containing Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ perovskite at IT. The high natural abundance of iron means they are relatively inexpensive and have a good thermal expansion match with the electrolytes.…”

Section: Introductionmentioning

confidence: 76%

“…Alternatively A-site deficiencies can be created, which can either increase the concentration of oxygen vacancies or promote charge hopping sites (e. g. mixed-valent metal couples such as Fe 3 + /Fe 4 + ). [26][27][28][29] In our recent work, a synergistic effect was observed from both the doped monovalent Li or K ions and the A-site deficiency, which bestows the pristine SrFe 0.8 Nb 0.1 Ta 0.1 O 3-δ perovskite with a remarkably high ORR activity even comparable to the benchmark cobalt-containing Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ perovskite at IT. [30] In particular, we found that the size mismatch of Li + (0.92 Å) dopant with the Sr 2 + (1.64 Å) host could also render a significant amount of Li + migrating to the surface and creating A-site deficiency in the bulk at high temperature.…”

Section: Introductionmentioning

confidence: 76%

Unveiling Lithium Roles in Cobalt‐Free Cathodes for Efficient Oxygen Reduction Reaction below 600 °C

Rehman

Knibbe

et al. 2019

ChemElectroChem

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Improving the sluggish electrocatalytic oxygen reduction reaction (ORR) over cobalt-free cathodes at 550-800°C is imperative to circumvent challenges faced by practical operation of intermediate temperature solid oxide fuel cells. In this work, we synthesize novel cobalt-free, lithium (Li)-doped, perovskite oxides Sr 1-x Li x Fe 0.8 Nb 0.1 Ta 0.1 O 3-δ (SLFNTx, x = 0-0.1) as cathodes for efficient ORR catalysis. When the Li concentration is less than 0.05, ORR activity is enhanced by over 1.6-fold in comparison to the undoped SFNT below 600°C in both symmetrical and anode-supported single cells configurations. Our comprehensive investigation over crystal structure, surface, and mixed conductivities revealed that a moderate concentration (< 0.05) of Li could bestow the perovskite with a stable cubic perovskite structure that contains an optimal concentration of oxygen vacancies and A-site deficiencies. Such trend originates from the lower electronegativity and smaller size of Li dopant than the strontium host. The lower electronegativity increases oxygen vacancies. The small Li dopant induces thermal-migration of Li species and creates A-site deficiency. These insights highlight an effective strategy to advance the performance of cobalt-free ORR electrocatalyst below 600°C through in situ thermal surface migration of the A-site cations.

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Enhanced reducibility and conductivity of Na/K-doped SrTi0.8Nb0.2O3

Cited by 22 publications

References 25 publications

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

Unveiling Lithium Roles in Cobalt‐Free Cathodes for Efficient Oxygen Reduction Reaction below 600 °C

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