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Abstract: We found high activity and durability for oxide-supported Pt catalysts for the oxygen reduction reaction (ORR). These catalysts were supported on Sn0.96Nb0.04O2–δ (Pt/Sn0.96Nb0.04O2–δ ; BET area of support, 37m2 g−1; Pt loading, 10.0wt%) and Sn0.96Sb0.04O2–δ (Pt/Sn0.96Sb0.04O2–δ ; BET area of support, 33m2 g−1; Pt loading, 12.3wt%), by use of the rotating disk electrode (RDE) technique, and measured the I–E performance of single H2-air polymer electrolyte fuel cells (PEFCs) using these catalysts as the cathode. The nanoparticulate supports Sn0.96Nb0.04O2–δ and Sn0.96Sb0.04O2–δ had an aggregated structure similar to that of carbon black (CB). The electrochemically active surface area of Pt, estimated by cyclic voltammetry measurements with the RDE, reached 79.7m2 g−1 (Pt/Sn0.96Nb0.04O2–δ ) and 68.6 m2 g−1 (Pt/Sn0.96Sb0.04O2–δ ). The ORR activity of Pt/Sn0.96Nb0.04O2–δ exceeded that of a commercialized Pt catalyst supported carbon black (Pt/CB). Higher durability was confirmed for Pt/Sn0.96Nb0.04O2–δ and Pt/Sn0.96Sb0.04O2–δ compared to that of Pt/CB with a test protocol for start/stop cycling recommended by the Fuel Cell Commercialization Conference of Japan (FCCJ) [1]. Single cells using these catalysts showed I–E performance superior to that for the Pt/CB at operating potentials above 0.4V. For operating potentials below 0.4V, a slight amount of Sn dissolution from the Sn0.96Sb0.04O2–δ support occurred, resulting in degradation of the cell performance due to Pt poisoning by Sn re-deposition, but no noticeable degradation at Sn0.96Nb0.04O2–δ was found, due to the suppressed Sn dissolution. [Copyright &y& Elsevier]

Abstract: We synthesized a Pt catalyst supported on Sn0.96Sb0.04O2−δ with a random network structure for the cathode of the polymer electrolyte fuel cell (PEFC). The Sn0.96Sb0.04O2−δ support, synthesized by the flame combustion method, was in the form of nanometer-sized particles with a partially agglomerated structure similar to that of carbon black (CB) and with a high surface area, 125m2 g−1. The structure was considered to be beneficial in reducing the contact resistance between the Sn0.96Sb0.04O2−δ support particles and in dispersing the nanometer-size Pt particles. We applied the nanocapsule method to synthesize the Sn0.96Sb0.04O2−δ -supported Pt catalyst (Pt/Sn0.96Sb0.04O2−δ ). The electrochemically active surface area (ECA) of Pt reached a maximum of 60.2m2 g(Pt) −1, and the high values were maintained during the potential step cycling test (0.9–1.3V) simulating the start/stop cycling of PEFCs. The oxygen reduction reaction activity of the Pt/Sn0.96Sb0.04O2−δ catalyst exceeded that of Pt supported on carbon black (Pt/CB). We conclude that the random network structured Sn0.96Sb0.04O2−δ might be a good candidate support material for the cathode of PEFCs. [Copyright &y& Elsevier]

Here we report, for the first time, the synthesis of highly crystalline novel mesoporous carbon/nitrogen (C/N)-codoped TiO2 (MCNT) using ethylene diamine and carbon tetrachloride as the source for nitrogen and carbon, KIT-6 as the template, and titanium tetraisopropoxide as the TiO2 source. The obtained material has been unambiguously characterized by various sophisticated techniques. XRD and TEM analysis revealed that the MCNT material possesses highly crystalline 3D structure with a continuous network of mesoporous channels as well as structure corresponding to TiO2. UV-DRS analysis indicated that light absorption shifted to lower energy and stronger absorption in the visible light region. XPS revealed that C and N were doped effectively and C or N dopants might be present in the chemical environment of Ti–O–N or Ti–O–C. It has been found that the material is highly crystalline and possesses high surface area, pore volume and uniform pore size distribution. Owing to its textural characteristics, it could be useful for various applications, such as photocatalysis, fuel cells, bulky biomolecule adsorption and nanotechnology. [ABSTRACT FROM AUTHOR]

Abstract: The electrical resistivity of the Zn1−x−y Ga x In y O system was investigated as a function of the dopant content and mean dopant ion radius. The electrical resistivity of all members of the system exhibited metallic behavior as a function of temperature. The lowest electrical resistivity at 873K fell to 2.81×10−3 (Ωcm) in Zn0.99Ga0.0073In0.0027O. In cases with the same dopant content, the resistivity strongly depended on the mean dopant ion radius, but the Seebeck coefficient was unrelated to those radii. Regardless of dopant content, the minimum resistivity of this system appeared around a mean dopant ion radius of 0.54Å. Evidently, the carrier mobility is strongly dependent on the magnitude of the mean dopant ion radius and any structural distortion. [Copyright &y& Elsevier]

Abstract: We have measured the electrical power density of a single cell of a solid oxide fuel cell (SOFC) with (Ba0.3Sr0.2La0.5)InO2.75 as an electrolyte at an operating temperature of 800 °C. A moistened mixture of 10% hydrogen in argon, constituted the fuel gas; air was the oxidant gas. We selected (La0.6Sr0.4)(Mn1−x M x )O3−δ (M =Co, Ni) (x =0–0.3) and Ni as cathode and anode materials. The power density was dependent on the amount of the transition metal doped into the cathode; the use of (La0.6Sr0.4)(Mn0.9Co0.1)O3−δ as a cathode material enabled us to reach a maximum power density of 0.61 W/cm2. We also investigated the diffusion of the constituent elements around the interface between the cathode and the electrolyte by X-ray diffraction and X-ray energy dispersive analysis (EDX). We found that the constituent elements Mn, Co, Ni and In diffused to the opposite phase. We suggest that this cation diffusion would change the electrical conductivity of the cathode and electrolyte around the interface and would affect the cathodic reaction. The interface resistance between the (Ba0.3Sr0.2La0.5)InO2.75 electrolyte and the (La0.6Sr0.4)(Mn1−x M x )O3−δ (M =Co and Ni) (x =0–0.3) cathode was characterized by the direct current two-probe method. It showed minimum values at x =0.1(Co) and x =0.2(Ni), suggesting that the interface properties might strongly affect the power generation of the SOFC. [Copyright &y& Elsevier]

The proton conductivity of (Ba1− x La x )2In2O5+ x system has been investigated as a function of the La content, temperature and amount of absorbed water. The proton conductivity increased with La content up to x = 0.10, to reach a maximum of 1.12 × 10−5 (S/cm) at 400 °C. From that point on, it decreased. From the results of thermogravimetry and mass spectra, we confirmed that the water was absorbed in the (Ba1− x La x )2In2O5+ x system, in a maximum quantity of 0.14 mol/mol (sample). The proton conductivity increased monotonically with the quantity of water uptake, suggesting that this variable is one of the dominant parameter of proton conductivity in this system. [ABSTRACT FROM AUTHOR]

The proton conductivity of (Ba1− x La x )2In2O5+ x system has been investigated as a function of the La content, temperature and amount of absorbed water. The proton conductivity increased with La content up to x = 0.10, to reach a maximum of 1.12 × 10−5 (S/cm) at 400 °C. From that point on, it decreased. From the results of thermogravimetry and mass spectra, we confirmed that the water was absorbed in the (Ba1− x La x )2In2O5+ x system, in a maximum quantity of 0.14 mol/mol (sample). The proton conductivity increased monotonically with the quantity of water uptake, suggesting that this variable is one of the dominant parameter of proton conductivity in this system. [ABSTRACT FROM AUTHOR]

Abstract: We have synthesized the perovskite oxides of the (Ba0.3Sr0.2La0.5)(In1−x Fe x )O3−δ system and measured the total electrical conductivity as a function of temperature and oxygen partial pressure. It was found that the single-phase composition region extended from x =0.0 to x =1.0, and that the Fe valence increased from 3.06 to 3.50 in that region. The electrical conductivity was semiconducting from x =0.0 to x =0.40 and metallic from x =0.50 to x =1.0. The total electrical conductivity at 800 °C also increased with the Fe content and achieved a maximum value of 140 (S/cm) at x =1.0. From the dependence of the electrical conductivity on the oxygen partial pressure, we conclude that above x =0.50, the majority carriers are holes. The estimated hole conductivity increased exponentially with the amount of Fe4+ cation present. The oxide ion conductivity was dependent on the oxygen vacancy content. [Copyright &y& Elsevier]

Abstract: We have conducted an electrical power generation experiment using a single cell of solid oxide fuel cell (SOFC) with (Ba0.3Sr0.2La0.5)InO2.75 as an electrolyte at an operating temperature of 800 °C. A moistened 10% hydrogen/argon mixture constituted the fuel gas, and air was the oxidant gas. As cathode and anode materials, we selected (La0.6Sr0.4)(Mn1−x Fe x )O3−δ (x =0–0.6) and Ni, respectively. The power density proved to be dependent on the Fe content of the cathode; use of (La0.6Sr0.4)(Mn0.6Fe0.4)O3−δ as a cathode material enabled us to reach a maximum power density of 0.58 W/cm2. An analysis of X-ray Absorption Near-Edge Structure (XANES) taken to detect mixed valence of Mn and Fe showed that each valence was over 3.0. We also investigated, by X-ray diffraction and energy dispersive X-ray analysis (EDX), the diffusion of the constituent elements around the interface between the cathode and the electrolyte. Our results showed that the Mn, Fe and In diffused to the opposite phase. The interface resistance between electrolyte and electrode, which was measured by the direct current two-probe method, reached a minimum value at x =0.4, suggesting that the electronic conductivity of the interface would strongly affect the power generation. [Copyright &y& Elsevier]

Abstract: A solid oxide fuel cell (SOFC) in which (Ba0.3Sr0.2La0.5)InO2.75 was used as an electrolyte was fabricated in order to characterize its electrical power generation. Moistened 1% hydrogen gas balanced with argon gas was used as the fuel gas to prevent reduction of the electrolyte. The chemical reaction between the electrolyte and some electrode materials has been investigated by X-ray diffraction. The appropriate electrodes are Pt and Ni for the cathode and anode, respectively. The maximum power density was 0.51 (W/cm2) at 800 °C. [Copyright &y& Elsevier]

Total electrical conductivity of (Ba0.5+xLa0.5-x)2(In1-xMx)2O5.5 (M=Zr and Ce) and (Ba0.5-xLa0.5+x)2(In1-xMx′)2O5.5 (M′=Mg, Ca and Sr) solid-solution systems was measured as functions of temperature and oxygen partial pressure. The oxide-ion conductivity of all the solid-solution systems increased at first with an increase in the unit cell free volume. However, it showed a maximum value at a unit cell free volume and then decreased. All the solid-solution systems showed a similar dependence of the oxide-ion conductivity on the unit cell free volume, even if they have different average ionic valences in the A- and B-sites. From the results of the Raman spectra measurement, the decrease of conductivity in the larger unit cell free volume range is presumed to arise from the local distortion of oxygen octahedra. [Copyright &y& Elsevier]

Electrical conductivity of the fluorite-type solid-solution system Zr0.7(Sc1- xM x)0.3O2-δ (M=Ca, Mg, Al, Gd, Yb) was systematically investigated from the viewpoint of a stabilization effect of the cubic phase. The rhombohedral phase of Zr0.7Sc0.3O1.85 transformed to the cubic phase by the partial substitution of M for Sc. At the same time, the electrical conductivity abruptly increased. The electrical conductivity of the cubic phase decreased linearly and gradually with increase in oxygen vacancy content, but nevertheless the kind of dopants, and the extrapolated value of the conductivity to δ=0.25 agreed with that of a pyrochlore-type La2Zr2O7. This fact was understood by considering that the partial substitution of M ions in place of Sc produced a micro-cluster having a pyrochlore-type structure with cubic symmetry. [ABSTRACT FROM AUTHOR]

To improve the properties of quaternized QPAF‐4 copolymers as anion exchange membranes, compositing with hydrophilic Ta–TiO2 particles are investigated. Flexible QPAF‐4/Ta–TiO2 composite membranes are obtained using solution‐casting and die coating methods. Cross‐sectional scanning electron microscopy reveals that the die coating method produces a more homogenous and uniform distribution of Ta–TiO2 particles in the composite membranes than the solution‐casting method. The Ta‐TiO2 particles promotes the suppression of water absorbability and dimensional swelling of the composite membranes which is more pronounced in the die coated membranes. The Ta–TiO2 increase hydroxide ion conductivity to 116.9 mS cm−1 at 80 °C for the die‐coated membrane, surpassing that of the pristine QPAF‐4 membrane (92 mS cm−1). Ta–TiO2 with the composite membranes survive in 4 m KOH at 80 °C for 1000 h, maintaining 96–112 mS cm−1 (88–99% remaining) of initial conductivity. All composite membranes exhibit higher mechanical robustness (elongation of >200%), with the die‐coated composite membranes. The optimized die coated composite membrane is fabricated in an alkaline water electrolysis cell achieving 1.63 V at 1.0 A cm−2 (75.5% efficiency). [ABSTRACT FROM AUTHOR]

Alkaline‐stable, highly conductive anion exchange membranes (AEMs) are attentively expected solid polymer electrolytes that contribute to achieving high performance and durability for anion exchange membrane water electrolyzers (AEMWEs). The technical challenges of AEMs mainly stem from the degradation of the polymer backbones, side chains, and anchoring cationic groups. Herein, new and stable AEMs (QTAF) are designed using 3,3′′‐dichloro‐2′,5′‐bis(trifluoromethyl)‐1,1′:4′,1′′‐terphenyl (TFP) monomers as the hydrophobic component incorporated into the polyphenylene backbone and 3,3′‐(2,7‐dichloro‐9H‐fluorene‐9,9‐diyl)bis(N,N‐dimethylpropane‐1‐amine) (AF) monomers as the hydrophilic component. After tuning the copolymer composition, the highest hydroxide ion conductivity (168.7 mS cm−1 at 80 °C) is achieved with the QTAF‐3.0 membrane. The QTAF‐3.0 membrane survives in harsh alkaline conditions (8 M KOH solution, 80 °C), with high conductivity (75.8 mS cm−1) after 810 h. A water electrolysis cell with QTAF‐3.0 membrane and non‐noble Ni0.8Co0.2O anode catalyst operates stably at a constant current density (1.0 A cm−2) for 1000 h with a negligible voltage increase rate of 1.1 µV h−1 after the initial voltage increase. The water electrolysis performance of the post‐tested QTAF‐3.0 cell is 1.83 V, only a 6.4% increase from the initial performance at 2.0 A cm−2, suggesting the high potential of the QTAF‐3.0 membrane for practical AEMWE applications. [ABSTRACT FROM AUTHOR]