| 1. |
- Abdalla, Abdalla M., et al.
(författare)
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Synthesis and characterization of Sm1-xZrxFe1-yMgyO3 (x, y = 0.5, 0.7, 0.9) as possible electrolytes for SOFCs
- 2018
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Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 765 KEM, s. 49-53
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Konferensbidrag (refereegranskat)abstract
- The novel perovskite oxide series of Sm 1-x Zr x Fe 1-y Mg y O 3 (x,y = 0.5, 0.7, 0.9) were synthesized by solid state reaction method. X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and conductivity analysis were carried out. XRD patterns of sintered materials revealed the shifted Bragg reflection to higher angle for the higher content of Zr and Mg. This is related to the ionic size of the dopant elements. Rietveld refinement showed that all compounds crystallized in cubic space group of Fm-3m. SEM images showed that the grains were well defined with highly dense surfaces makes it potential as an electrolyte material in solid oxide fuel cells (SOFCs) or gases sensors. Impedance spectroscopy at 550-800 °C shows that conductivity is higher at higher temperature. Sm 0.5 Zr 0.5 Fe 0.5 Mg 0.5 O 3 shows the highest conductivity of 5.451 × 10 -3 S cm -1 at 800 °C. It was observed that 50% molar ratio of Mg and Zr doping performed highest conductivity.
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| 2. |
- Afif, A., et al.
(författare)
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Advanced materials and technologies for hybrid supercapacitors for energy storage – A review
- 2019
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Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X. ; 25:October 2019
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Forskningsöversikt (refereegranskat)abstract
- Supercapacitors have become the most significant energy conversion and storage system in recent renewable and sustainable nanotechnology. Due to its large energy capacity and supply with relatively short time and longer lifetime, supercapacitors breakthrough in advance energy applications. This review presents a comparative study of different materials, working principles, analysis, applications, advantages and disadvantages of various technologies available for supercapacitors. The aim of this article is to discuss the possibility of hybrid supercapacitor for the next generation of energy technology. The development of composite materials containing a wide range of active constituents (e.g., graphene, activated carbon, transition metals, metal oxides, perovskites and conducting polymers) by in-situ hybridization and ex-situ recombination is also discussed. This review consecrated largely the contribution of combining all materials (electrode and electrolyte) and their synthesis process and electrochemical performance. Enduringly, the potential issues and the perspectives for future research based on hybrid supercapacitors in energy applications are also presented.
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| 3. |
- Afif, A., et al.
(författare)
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Ceramic fuel cells using novel proton-conducting BaCe 0.5 Zr 0.3 Y 0.1 Yb 0.05 Zn 0.05 O 3-δ electrolyte
- 2022
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1433-0768 .- 1432-8488. ; 1:26, s. 111-120
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Tidskriftsartikel (refereegranskat)abstract
- Protonic ceramic fuel cells have become extremely interesting due to their high power output at the intermediate temperature range (400–700 °C). Significant progress has been made to develop electrolyte materials, doped barium cerates-zirconate, which gets the leading role due to its high chemical stability and high ionic conductivity. Here, we present a new composition BaCe0.5Zr0.3Y0.1Yb0.05Zn0.05O3-δ (BCZYYbZn05), where addition of 5 mol% Zn with Ce, Zr, Y, and Yb at the B-site of the perovskite material shows high stability with high conductivity. The material was synthesized by solid-state reaction route at 1400 °C which showed 98% relative density. Rietveld analysis of neutron powder diffraction data reveal an orthorhombic structure with Pbnm space group. Thermogravimetric analysis shows about 1.06% weight loss from 200 to 1000 °C which is mainly related to the formation of the oxygen vacancies. In wet hydrogen atmosphere, this material shows higher conductivity and lower activation energy than dry hydrogen atmosphere indicates the conduction type as protonic conduction. The anode-supported single test cell based on this electrolyte material demonstrates peak power densities 649 mW cm−2 at 700 °C using conventional BSCF cathode, representing an important step toward commercially viable SOFC technology.
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| 4. |
- Afif, A., et al.
(författare)
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Electrochemical and structural characterization of BaCe 0.7 Zr 0.15 Y 0.1 Zn 0.05 O 3-δ as an electrolyte for SOFC-H
- 2018
-
Ingår i: IET Conference Publications. ; 2018:CP750
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Konferensbidrag (refereegranskat)abstract
- As a potential electrolyte for proton-conducting solid oxide fuel cells (SOFC-Hs) and to get better protonic conductivity and stability, zinc doped BCZY material has been found to be promising. In this study, we report a new composition of proton conductors BaCe0.7Zr0.15Y01Zn0.05O3-s (BCZYZn10) which was investigated using XRD, SEM and conductivity measurements. Rietveld refinement of the XRD data revel a cubic perovskite structure with Pm-3m space group. Rietveld analysis of BaCe07Zr0.15Y01Zn0.05O3-5 shows the unit cell parameter is a = 4.3582(7) A. Scanning electron microscopy images shows that the grain sizes are large and compact which gives the sample high density and good protonic conductivity. The total conductivity in wet atmosphere is significantly higher than that of dry condition and the conductivity was found to be 0.004032 Scm-1 and 0.00164 Scm-1 at 600 °C in wet and dry Ar, respectively. This study indicated that perovskite electrolyte BCZYZn10 is a promising material for the next generation intermediate temperature solid oxide fuel cells (IT-SOFCs).
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| 5. |
- Afif, Ahmed, et al.
(författare)
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Enhancement of proton conductivity through Yb and Zn doping in BaCe0.5Zr0.35Y0.15O3-delta electrolyte for IT-SOFCs
- 2018
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Ingår i: Processing and Application of Ceramics. - : National Library of Serbia. - 2406-1034 .- 1820-6131. ; 12:2, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- The new compositions of BaCe0.5Zr0.3Y0.15-xYbxZn0.05O3-delta perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500 degrees C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm-3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500 degrees C. The protonic conductivities at 650 degrees C were 2.8x10(-4) S/cm and 4.2x10(-3) S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system.
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| 6. |
- Afif, A., et al.
(författare)
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Scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2, 0.3) for possible application in Solid Oxide Fuel Cell electrolytes
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). Polycrystalline scheelite type Sr1−xBaxWO4 (x = 0.1, 0.2 & 0.3) materials were synthesized by the solid state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. All compounds crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. SEM illustrates the highly dense compounds. Significant mass change was observed to prove the proton uptake at higher temperature by TG-DSC. All compound shows lower conductivity compared to the traditional BCZY perovskite structured materials. SBW with x = 0.3 exhibit the highest ionic conductivity among all compounds under wet argon condition which is 1.9 × 10−6 S cm−1 at 1000 °C. Since this scheelite type compounds show significant conductivity, the new series of SBW could serve in IT-SOFC as proton conducting electrolyte.
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| 7. |
- Afif, A., et al.
(författare)
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Structural and electrochemical characterization of BaCe0.7Zr0.2Y0.05Zn0.05O3 as an electrolyte for SOFC-H
- 2016
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Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 121:1
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Konferensbidrag (refereegranskat)abstract
- As a potential electrolyte for proton-conducting solid oxide fuel cells (SOFC-Hs) and to get better protonic conductivity and stability, zinc doped BCZY material has been found to be promising. In this study, we report a new composition of proton conductors BaCe0.7Zr0.2Y0.05Zn0.05O3 (BCZYZn5) which was investigated using XRD, SEM and conductivity measurements. Rietveld refinement of the XRD data revel a cubic perovskite structure with Pm-3m space group. BaCe0.7Zr0.2Y0.05Zn0.05O3 shows cell parameter a = 4.3452(9) Å. Scanning electron microscopy images shows that the grain sizes are large and compact which gives the sample high density and good protonic conductivity. The total conductivity in wet atmosphere is significantly higher than that of dry condition and the conductivity was found to be 0.276 × 10-3 Scm-1 and 0.204 × 10-3 Scm-1 at 600°C in wet and dry Ar, respectively. This study indicated that perovskite electrolyte BCZYZn5 is a promising material for the next generation intermediate temperature solid oxide fuel cells (IT-SOFCs).
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| 8. |
- Afif, A., et al.
(författare)
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Structural study and proton conductivity in BaCe0.7Zr0.25-xYxZn0.05O3 (x=0.05, 0.1, 0.15, 0.2 & 0.25)
- 2016
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 41:27, s. 11823-11831
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Tidskriftsartikel (refereegranskat)abstract
- Solid oxide fuel cell (SOPC) has been considered to generate power represented by conductivity. Zinc doped Barium Cerium Zirconium Yttrium oxide (BCZYZn) has been found to offer high protonic conductivity and high stability as being electrolyte for proton conducting SOFCs. In this study, we report a new series of proton conducting materials, BaCe0.7Zr0.25-xYxZn0.05O3 (x = 0.05, 0.1, 0.15, 0.2 and 0.25). The materials were synthesized by solid state reaction route and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal expansion, particle size and impedance spectroscopy (IS). Rietveld analysis of the XRD data reveal a cubic perovskite structure with Pm-3m space group up to composition x = 0.15. For x = 0.15 and 0.20, the materials have structural phase change to orthorhombic in the Pbnm space group. Scanning electron microscopy images show high density materials. Thermal expansion measurements show that the thermal expansion coefficient is in the range 10.0-11.0 x 10(-6)/degrees C. Impedance spectroscopy shows higher ionic conduction under wet condition compared to dry condition. Y content of 25% (BCZYZn25) exhibits highest conductivity of 1.84 x 10(-2) S/cm in wet Argon. This study indicated that perovskite electrolyte BCZYZn is promising material for the next generation of intermediate temperature solid oxide fuel cells (IT-SOFCs).
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| 9. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Effect of co-doping on proton conductivity in perovskite oxides BaZr0.9In0.05M0.05O3−δ (M = Yb3+ or Ga3+)
- 2010
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 35:12, s. 6381-6391
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Tidskriftsartikel (refereegranskat)abstract
- BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) has been prepared by solid-statesynthesis route.Rietveld analysis of neutron powder diffraction data on as-prepared samples showed thatboth samples crystallise in the cubic space group Pm-3m. Scanning electron microscopyanalysis showed that the grains intheBaZr0.9In0.05Ga0.05O3-d sample were larger than the BaZr0.9In0.05Yb0.05O3-d sample. Dynamic thermogravimetric analysis indicates that the proton concentration was higher inpre-hydrated BaZr0.9In0.05Ga0.05O3-d sample (40%oftheoretical)than that of BaZr0.9In0.05Yb0.05O3-d sample (28%oftheoretical).Proton conductivity was studied on pre-hydrated samples(under both dry and wetAr atmospheres).Thebulk proton conductivities of the heating cycle of pre-hydrated BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) samples were 2.1 * 10-5 S cm-1 and 1.9 * 10-4 Scm-1 at 350C, respectively.The effect of co-doping onproton conductivity was investigatedand the results are compared with single doped systems e.g. BaZr0.9M0.1O3-d (M=Ga3+, In3+ orYb3+) samples.
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| 10. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr[sub 0.5]In[sub 0.25]Yb[sub 0.25]O[sub 3 - delta]
- 2010
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Ingår i: Journal of The Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:12
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Tidskriftsartikel (refereegranskat)abstract
- A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.5×10−4 and 2.2×10−5 S cm−1, respectively, at 300°C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200°C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.3×10−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs.
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| 11. |
- Bielecki, Johan, 1982, et al.
(författare)
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Short-range structure of the brownmillerite-type oxide Ba2In2O5 and its hydrated proton-conducting form BaInO3H
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:40, s. 16915-16924
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Tidskriftsartikel (refereegranskat)abstract
- The vibrational spectra and short-range structure of the brownmillerite-type oxide Ba2In2O6 and its hydrated form BaInO3H, are investigated by means of Raman, infrared, and inelastic neutron scattering spectroscopies together with density functional theory calculations. For Ba2In2O6, which may be described as an oxygen deficient perovskite structure with alternating layers of InO6 octahedra and InO4 tetrahedra, the results affirm a short-range structure of Icmm symmetry, which is characterized by random orientation of successive layers of InO4 tetrahedra. For the hydrated, proton conducting, form, BaInO3H, the results suggest that the short-range structure is more complicated than the P4/mbm symmetry that has been proposed previously on the basis of neutron diffraction, but rather suggest a proton configuration close to the lowest energy structure predicted by Martinez et al. [J.-R. Martinez, C. E. Moen, S. Stoelen, N. L. Allan, J. Solid State Chem., 180, 3388, (2007)]. An intense Raman active vibration at 150 cm(-1) is identified as a unique fingerprint of this proton configuration.
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| 12. |
- Biendicho, Jordi Jacas, et al.
(författare)
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The Fluorite-Like Phase Nd5Mo3O16 +/-delta in the MoO3-Nd2O3 System: Synthesis, Crystal Structure, and Conducting Properties
- 2018
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:12, s. 7025-7035
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a study of the system MoO3-Nd(2)O(3)using a combination of X-ray powder diffraction (XRD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), and ac impedance spectroscopy (IS). A phase-pure material is observed at a composition of 45.5 mol % Nd2O3, which corresponds to an ideal stoichiometry of Nd5Mo3O16.5. XRD and NPD show that the crystal structure is a superstructure of the fluorite arrangement, with long-range ordering of the two cation species leading to a doubled unit cell parameter. The sample is found to be significantly oxygen deficient, i.e. Nd5Mo3O15.63(4), when it is prepared by a solid-state reaction at 1473 K in air. TGA measurements indicate that the sample loses only minimal mass on heating to 1273 K in O-2. IS studies of the mean conductivity under different atmospheres show that the sample is a mixed conductor between ambient temperature and 873 K, with a dominant electronic component at higher temperatures, as demonstrated by measurements under inert atmosphere. NPD measurements indicate that the anion vacancies are preferentially located on the O2 sites, while studies of the temperature dependence performed under an O(2)atmosphere to 1273 K show significantly anisotropic thermal parameters of the anions. Together with analysis of the total neutron scattering data, this supports a model of oxygen ions hopping between O2 positions, with a vacancy, rather than interstitial, mechanism for the anion diffusion.
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| 13. |
- Bjorheim, T. S., et al.
(författare)
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Hydration thermodynamics of the proton conducting oxygen-deficient perovskite series BaTi1- xMxO3- x /2 with M = in or Sc
- 2015
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 54:6, s. 2858-2865
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Tidskriftsartikel (refereegranskat)abstract
- This article establishes the effect of structure and composition on water uptake and the hydration and proton transport properties of the oxygen-deficient perovskite series BaTi1-x(In,Sc)xO3-x/2, with 0.2 ≤ x ≤ 0.7. The equilibrium water uptake is determined by thermogravimetry, while combining thermogravimetry with differential scanning calorimetry allows for direct determination of the materials hydration thermodynamics. Proton and oxide ion transport properties are characterized by means of ac impedance measurements up to 1000 °C. In general, the hydration thermodynamics of the scandates are more favorable than that of the indates and are also affected by changes in crystal structure throughout the series. The more favorable hydration thermodynamics of cubic scandates increase their proton conductivity at higher temperatures compared to their indate counterparts. In contrast to the BaTi1-xInxO3-x/2 series, the BaTi1-xScxO3-x/2 (0.5 ≤ x ≤ 0.7) materials retain their cubic structures upon full saturation by protons and show no signs of chemical instability upon exposure to 1 atm H2O(g) down to 100 °C. The BaTi1-xScxO3-x/2 materials with 0.5 ≤ x ≤ 0.7 may therefore find application in, for instance, steam electrolysis or similar processes involving high water vapor pressures.
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| 14. |
- Chernov, S. V., et al.
(författare)
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Sr2GaScO5, Sr10Ga6Sc4O25, and SrGa0,75Sc0,25O2,5: a Play in the Octahedra to Tetrahedra Ratio in Oxygen-Deficient Perovskites
- 2012
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 51:2, s. 1094-1103
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Tidskriftsartikel (refereegranskat)abstract
- Three different perovskite-related phases were isolated in the SrGa(1-x)Sc(x)O(2.5) system: Sr(2)GaScO(5), Sr(10)Ga(6)Sc(4)O(25), and SrGa(0.75)Sc(0.25)O(2.5), Sr(2)GaScO(5) (x = 0.5) crystallizes in a brownrnillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) angstrom, b = 15.1594(1) angstrom, and c = 5.70926(4) angstrom] with complete ordering of Sc(3+) and Ga(3+) over octahedral and tetrahedral positions, respectively. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4(1)/a, a = 17.517(1) angstrom, c = 32.830(3) angstrom]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) can be described as a stacking of eight perovskite layers along the c axis ...[-(Sc/Ga)O(1.6)-SrO(0.8)-(Sc/Ga)O(1.8)-SrO(0.8)-](2 center dot center dot center dot) Similar to Sr(2)GaScO(5), this structure features a complete ordering of the Sc(3+) and Ga(3+) cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr(10)Ga(6)Sc(4)O(25) is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc(3+) by Ga(3+) leads to the formation of the cubic perovskite phase SrGa(0.75)Sc(0.25)O(2.5) (x = 0.25) with a = 3.9817(4) angstrom. This compound incorporates water molecules in the structure forming SrGa(0.75)Sc(0.25)O(2.5)center dot xH(2)O hydrate, which exhibits a proton conductivity of similar to 2.0 x 10(-6) S/cm at 673 K.
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| 15. |
- Gustavsson, John, et al.
(författare)
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In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes
- 2012
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Ingår i: Journal of Electrochemical Science and Engineering. - : International Association of Physical Chemists (IAPC). - 1847-9286. ; 2:3, s. 105-120
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Tidskriftsartikel (refereegranskat)abstract
- Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.
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| 16. |
- Hossain, S., et al.
(författare)
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Highly dense and chemically stable proton conducting electrolyte sintered at 1200 °C
- 2018
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 43:2, s. 894-907
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Tidskriftsartikel (refereegranskat)abstract
- The BaCe 0.7 Zr 0.1 Y 0.2−x Zn x O 3−δ (x = 0.05, 0.10, 0.15, 0.20) has been synthesized by the conventional solid state reaction method for application in protonic solid oxide fuel cell. The phase purity and lattice parameters of the materials have been studied by the room temperature X-ray diffraction (XRD). Scanning electron microscopy (SEM) has been done for check the morphology and grain growth of the samples. The chemical and mechanical stabilities have been done using thermogravimetric analysis (TGA) in pure CO 2 environment and thermomechanical analysis (TMA) in Argon atmosphere. The XRD of the materials show the orthorhombic crystal symmetry with Pbnm space group. The SEM images of the pellets show that the samples sintered at 1200 °C are highly dense. The XRD after TGA in CO 2 and thermal expansion measurements confirm the stability. The particles of the samples are in micrometer ranges and increasing Zn content decreases the size. The conductivity measurements have been done in 5% H 2 with Ar in dry and wet atmospheres. All the materials show high proton conductivity in the intermediate temperature range (400–700 °C). The maximum proton conductivity was found to be 1.0 × 10 −2 S cm −1 at 700 °C in wet atmosphere for x = 0.10. From our study, 10 wt % of Zn seems to be optimum at the B-site of the perovskite structure. All the properties studied here suggest it can be a promising candidate of electrolyte for IT-SOFCs.
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| 17. |
- Hummelgård, Christine, et al.
(författare)
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Physical and electrochemical properties of cobalt doped (Ti,Ru)O-2 electrode coatings
- 2013
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Ingår i: Materials Science & Engineering B: Solid-State Materials for Advanced Technology. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 178:20, s. 1515-1522
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Tidskriftsartikel (refereegranskat)abstract
- The physical and electrochemical properties of ternary oxides Ti0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O-2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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| 18. |
- Martinelli, Anna, 1978, et al.
(författare)
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A New Solid-State Proton Conductor: The Salt Hydrate Based on Imidazolium and 12-Tungstophosphate
- 2021
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 143:34, s. 13895-13907
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Tidskriftsartikel (refereegranskat)abstract
- We report the structure and charge transport properties of a novel solid-state proton conductor obtained by acid-base chemistry via proton transfer from 12-tungstophosphoric acid to imidazole. The resulting material (henceforth named Imid3WP) is a solid salt hydrate that, at room temperature, includes four water molecules per structural unit. To our knowledge, this is the first attempt to tune the properties of a heteropolyacid-based solid-state proton conductor by means of a mixture of water and imidazole, interpolating between water-based and ionic liquid-based proton conductors of high thermal and electrochemical stability. The proton conductivity of Imid3WP·4H2O measured at truly anhydrous conditions reads 0.8 × 10-6 S cm-1 at 322 K, which is higher than the conductivity reported for any other related salt hydrate, despite the lower hydration. In the pseudoanhydrous state, that is, for Imid3WP·2H2O, the proton conductivity is still remarkable and, judging from the low activation energy (Ea = 0.26 eV), attributed to structural diffusion of protons. From complementary X-ray diffraction data, vibrational spectroscopy, and solid-state NMR experiments, the local structure of this salt hydrate was resolved, with imidazolium cations preferably orienting flat on the surface of the tungstophosphate anions, thus achieving a densely packed solid material, and water molecules of hydration that establish extremely strong hydrogen bonds. Computational results confirm these structural details and also evidence that the path of lowest energy for the proton transfer involves primarily imidazole and water molecules, while the proximate Keggin anion contributes with reducing the energy barrier for this particular pathway.
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| 19. |
- Noferini, Daria, 1983, et al.
(författare)
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Proton Dynamics in Hydrated BaZr0.9M0.1O2.95 (M = Y and Sc) Investigated with Neutron Spin-Echo
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:26, s. 13963-13969
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Tidskriftsartikel (refereegranskat)abstract
- Hydrated samples of the two proton conducting perovskites BaZr0.9M0.1O2.95 (M = Y and Sc) were investigated using neutron spin echo spectroscopy together with thermal gravimetric measurements, polarized neutron diffraction, and infrared spectroscopy, with the aim to determine how the atomic scale proton dynamics depend on temperature, and type of dopant atom, M. The results show the presence of pronounced localized proton motions for temperatures above ca. 300 K, characterized by relaxation times on the order of picoseconds to nanoseconds and governed by a wide distribution of activation energies due to a heterogeneous distribution of proton sites present, with no strong dependence on the type of dopant atom.
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| 20. |
- Noferini, Daria, 1983, et al.
(författare)
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Role of the doping level in localized proton motions in acceptor-doped barium zirconate proton conductors
- 2018
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 20:20, s. 13697-13704
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Tidskriftsartikel (refereegranskat)abstract
- Acceptor-doped barium zirconates are currently receiving considerable interest because of their high proton conductivity at intermediate temperatures, making them applicable as electrolytes in various electrochemical devices, but the mechanism of proton conduction is unclear. Here, we investigate the role of the acceptor-dopant level in the localized proton motions, i.e. proton transfers between oxygens and O-H reorientations, in hydrated samples of the proton conducting, acceptor-doped, perovskites BaZr1-xInxO3-x/2 with x = 0.10 and 0.20, using quasielastic neutron scattering (QENS). Analysis of the QENS spectra reveals that several proton transfer and O-H reorientational motions contribute to the QENS signal, as a consequence of the locally disordered nature of the structure due to the In doping of these materials, and establishes a generic and complex picture of localized proton dynamics in acceptor-doped barium zirconate based proton conductors. A comparison of the QENS results with vibrational spectroscopy data of the same materials, as reported in the literature, suggests a predominance of O-H reorientational motions in the observed dynamics. The highest doping level corresponds to a more distorted structure and faster dynamics, which thus indicates that some degree of structural disorder is favourable for high local proton mobility.
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| 21. |
- Norberg, Stefan, 1972, et al.
(författare)
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The proton conducting electrolyte BaTi0.5In0.5O2.75: determination of the deuteron site and its local environment
- 2013
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Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 25:45
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Tidskriftsartikel (refereegranskat)abstract
- Deuterated BaTi0.5In0.5O2.75 has been studied with neutron total (Bragg plus diffuse) scattering data, using both the Rietveld refinement method and the reverse Monte Carlo (RMC) modelling technique, to investigate the preferred proton site and its local structural environment. The Rietveld analysis shows an excellent fit between experimental data and a long-range cubic description of the BaTi0.5In0.5O2.53(OD)(0.44) perovskite structure containing a statistical distribution of Ti and In ions at the centre of regular (Ti/In)O-6 octahedra. However, an RMC analysis of the data reveals substantial local structural features that reflect limitations of the Rietveld method for studies of this type. The Ti-O and In-O pair distribution functions given by the RMC analysis are markedly different from each other, with average Ti-O and In-O bond distances of 2.035 angstrom and 2.159 angstrom, respectively. The InO6 octahedra are regular in shape whereas the TiO6 octahedra are distorted. The average O-D bond distance is roughly 0.96 angstrom, and the preferred deuteron sites have a second nearest oxygen distance of 2.13 angstrom, which confirms localized tilting of the deuteron and indicates a substantial degree of hydrogen bonding. The impact of octahedral distortion and hydrogen bonding on the proton conduction mechanism is discussed.
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| 22. |
- Perrichon, Adrien, 1988, et al.
(författare)
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Local structure and vibrational dynamics of proton conducting Ba2In2O5(H2O)x
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:29, s. 17626-17636
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Tidskriftsartikel (refereegranskat)abstract
- We study the local structure and vibrational dynamics of the brownmillerite-based proton conductors Ba2In2O5(H2O)x, with x = 0.30, 0.76, and 0.92, using infrared spectroscopy, inelastic neutron scattering and ab initio molecular dynamics simulations. Ba2In2O5(H2O)x is found to exhibit two main types of proton sites, H(1) and H(2). The H(1) site is characterised by the coexistence of two intra-octahedral hydrogen-bond geometries, whereas the H(2) site is characterised by inter-octahedral hydrogen bonding. While the strength of the hydrogen bonding is similar for the majority of protons in the two proton sites, ≈10% of the H(2) protons forms unusually strong hydrogen bonds due to local proton environments characterised by an unusually short oxygen-oxygen separation distance of ≈2.6 Å. These local proton environments are manifested as two O-H stretch bands in the infrared absorbance spectra, at 255 and 290 meV, respectively. These O-H stretch bands are as well observed in the related class of In-doped perovskite-type oxides, BaInyZr1-yO3-y/2 (0.25 ≤ y ≤ 0.75), suggesting that these perovskites may display brownmillerite-like distortions on a local length scale. In effect, these results point towards a clustering of the In atoms in these perovskite materials. Further, the infrared spectra of Ba2In2O5(H2O)x show a minor evolution as a function of x, because the protons tend to segregate into oxygen-rich hydrogen-rich domains upon dehydration. This points towards a highly anisotropic proton conduction mechanism in partially hydrated phases. This insight motivates efforts to identify ways to avoid phase separation, perhaps by suitable cation substitutions, as a route to accommodate high proton conductivity.
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| 23. |
- Radenahmad, N., et al.
(författare)
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High conductivity and high density proton conducting Ba1-xSrxCe0.5Zr0.35Y0.1Sm0.05O3-delta (x=0.5, 0.7, 0.9, 1.0) perovskites for IT-SOFC
- 2016
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 41:27, s. 11832-11841
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Tidskriftsartikel (refereegranskat)abstract
- Solid oxide fuel cell (SOFC) has been achieving attention in term of possibility in variety of fuels. Proton conductor enhanced conventional oxide conducting electrolyte has become more and more interesting particularly in intermediate operating temperature. Combination of doped BaCeO3 and BaZrO3 by doping Sr, Y and Sm was studied as the series of Ba1-xSrxCe0.5Zr0.35Y0.1Sm0.05O3-delta (BSCZYSm) by varying composition x = 0.5, 0.7, 0.9 and 1.0. The X-ray analysis reveals right-shifted peaks due to changing in unit cell volume. The cell parameters and density decreased with increasing Sr content. Rietveld refinement shows that all compositions crystallize in the cubic symmetry in the space group Pm-3m. Thermogravimetric analysis on dried and hydrated samples under nitrogen show significant weight change to prove the proton uptake at higher temperature. Scanning electron microscopy shows that the density is higher than 90% for all samples. BSCZYSm with x = 0.5 shows the highest conductivity in wet argon condition which is 2.391 x 10(-3) S cm(-1) at 700 degrees C. Particle size of materials were examined and reveal average diameter of 5.8 mu m approximately.
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| 24. |
- Radenahmad, N., et al.
(författare)
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Proton-conducting electrolytes for direct methanol and direct urea fuel cells - A state-of-the-art review
- 2016
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 57, s. 1347-1358
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Forskningsöversikt (refereegranskat)abstract
- This review focuses on the protonicisuperprotonic electrolytes used for application in direct methanol and direct urea/urine fuel cells. Since, methanol has. high energy density, which is essential for portable direct methanol fuel cells, and is simpler to store and transport than conventional hydrogen as fuel. However, methanol is not readily available, which makes waste an attractive option as a fuel source, resulting in the development of direct urea fuel cells. Fuel cells that use waste that contains hydrogen, like waste water or urine, are attractive because of their potential to generate energy from low-cost, abundant sources.
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| 25. |
- Rahman, Habibur Seikh Mohammad, 1976, et al.
(författare)
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Proton conductivity of hexagonal and cubic BaTi1-xScxO3-δ (0.1 ≤ x ≤ 0.8)
- 2014
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Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 43:40, s. 15055-15064
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Tidskriftsartikel (refereegranskat)abstract
- BaTi1−xScxO3−δ (x = 0.1–0.8) was prepared via solid state reaction. High resolution X-ray powder diffraction was used to characterise the synthesised materials. It was found that low substitution (x = 0.1 and 0.2) of Ti4+ for Sc3+ gives a hexagonal perovskite structure, whereas high substitution (x = 0.5–0.7) results in a cubic perovskite structure. Thermogravimetric analysis revealed significant levels of protons in both as-prepared and hydrated samples. Electrical conductivity was measured by AC impedance methods under oxygen, argon and under dry and humid, both H2O and D2O, conditions for BaTi1−xScxO3−δ (x = 0.2, 0.6 and 0.7). In the temperature range of 150–600 °C, under humid conditions, the conductivity is significantly higher than that under the dry conditions. The increase in conductivity is especially prominent for the cubic phases, indicating that protons are the dominant charge carriers. The proton conductivity of hexagonal BaTi0.8Sc0.2O3−δ is approx. two orders of magnitude lower than that of the more heavily substituted cubic phases. Conductivity is also found to be higher in dry O2 than in Ar in the whole temperature range of 150–1000 °C, characteristic of a significant contribution from p-type charge carriers under oxidising atmospheres. Greater Sc3+ substitution leads to a higher proton concentration and the highest proton conductivity (σ [similar] 2 × 10−3 S cm−1 at 600 °C) is found for the BaTi0.3Sc0.7O3−δ composition.
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