(La0.74Bi0.10Sr0.16)MnO3−δ–(Bi2O3)0.7(Er2O3)0.3 composite cathodes for intermediate temperature solid oxide fuel cells

(La_0.74Bi_0.10Sr_0.16)MnO_3−δ (LBSM)–(Bi₂O₃)_0.7(Er₂O₃)_0.3(ESB) composite cathodes were fabricated for intermediate-temperature solid oxide fuel cells with Sc-stabilized zirconia as the electrolyte. The performance of these cathodes was investigated at temperatures below 750 °C by AC impedance spectroscopy and the results indicated that LBSM–ESB had a better performance than traditional composite electrodes such as LSM–GDC and LSM–YSZ. At 750 °C, the lowest interfacial polarization resistance was only 0.11 Ω cm² for the LBSM–ESB cathode, 0.49 Ω cm² for the LSM–GDC cathode, and 1.31 Ω cm² for the LSM–YSZ cathode. The performance of the cathode was improved gradually by increasing the ESB content, and the performance was optimal when the amounts of LBSM and ESB were equal in composite cathodes. This study shows that the sintering temperature of the cathode affected performance, and the optimum sintering temperature for LBSM–ESB was 900 °C.     

Photosensitivity of p Si- n (GaSb)1 ? x ? y (Si2) x (GaAs) y , p Si- n (GaSb)1 ? x ? y (Si2) x (GaAs) y ,- n (GaSb) structures

Two-stage buffer n(GaSb)_{1 − x − y} (Si₂) _x (GaAs) _y and perfect n(GaSb) layers are grown on an pSi substrate by liquid-phase epitaxy from a tin solution-melt. It is shown that the photosensitivity of the pSi−n(GaSb)_{1 − x − y} (Si₂) _x (GaAs) _y structures is in the spectral range 1.0-1.6 eV, and that of the pSi − n (GaSb)_{1 − x − y} (Si₂) _x (GaAs) _{y − n} (GaSb) structures is in the range 0.62-1.15 eV. Original Russian Text ? A.S. Saidov, M.S. Saidov, Sh.N. Usmonov, D. Saparov, K.T. Kholikov, 2008, published in Geliotekhnika, 2008, No. 3, pp. 56–58.     

Metal-supported solid oxide fuel cells with in-situ sintered (Bi2O3)0.7(Er2O3)0.3–Ag composite cathode

Metal-supported solid oxide fuel cells (SOFCs) containing porous 430L stainless steel support, Ni-YSZ anode and YSZ electrolyte were fabricated by tape casting, laminating and co-firing in a reduced atmosphere. (Bi₂O₃)_0.7(Er₂O₃)_0.3–Ag composite cathode was applied by screen printing and in-situ sintering. The polarization resistances of the composite cathode were 1.18, 0.48, 0.18, 0.09 Ω cm² at 600, 650, 700 and 750 °C, respectively. A promissing maximum power density of 568 mW cm⁻² at 750 °C was obtained of the single cell. Short-term stability was measured as well.     

Enhanced hydrogen reversibility of nanoconfined LiBH4–Mg(BH4)2

This study shows the hydrogen desorption kinetics and reversible hydrogen storage properties of 0.55LiBH₄–0.45Mg(BH₄)₂ melt-infiltrated in different nanoporous carbon aerogels with different BET surface areas of 689 or 2660 m²/g and pore volumes of 1.21 or 3.13 mL/g. These investigations clearly show a significantly improved hydrogen storage capacity after four cycles of hydrogen release and uptake for bulk 0.55LiBH₄–0.45Mg(BH₄)₂ and infiltrated in carbon aerogel and the high surface area scaffold, where 22, 36 and 58% of the initial hydrogen content remain after four cycles of hydrogen release and uptake, respectively. Nanoconfinement in high surface area carbon aerogel appears to facilitate hydrogen release illustrated by release of 13.3 wt% H₂ (93%) and only 8.4 wt% H₂ (58%) from bulk hydride in the first cycle using the same physical condition. Notably, nanoconfinement also appear to have a beneficial effect on hydrogen uptake, since 8.3 wt% H₂ (58%) is released from the high surface area scaffold and only 3.1 wt% H₂ (22%) from the bulk sample during the fourth hydrogen release.     

Synthesis and evaluation of (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF)–Y0.08Zr0.92O1.96 (YSZ)–Gd0.1Ce0.9O2−δ (GDC) dual composite SOFC cathodes for high performance and durability

This paper investigates a (La_0.6Sr_0.4)(Co_0.2Fe_0.8)O₃ (LSCF)–Y_0.16Zr_0.92O_1.96 (YSZ)–Gd_0.1Ce_0.9O_2−δ (GDC) dual composite cathode to achieve better cathodic performance compared to an LSM/GDC–YSZ dual composite cathode developed in previous research. To synthesize the structures of the LSCF/GDC–YSZ and LSCF/YSZ–GDC dual composite cathodes, nano-porous composite cathodes containing LSCF, YSZ, and GDC were prepared by a two-step polymerizable complex (PC) method which prevents the formation of YSZ–GDC solid solution. At 800 °C, the electrode polarization resistance of the LSCF/YSZ–GDC dual composite cathode showed to be significantly lower (0.075 Ω cm²) compared to that of a commercial LSCF–GDC cathode (0.195 Ω cm²), a synthesized LSCF/GDC–YSZ dual composite cathode (0.138 Ω cm²), and an LSM/GDC–YSZ dual composite cathode (0.266 Ω cm²) respectively. Moreover, the Ni–YSZ anode-supported single cell containing the LSCF/YSZ–GDC dual composite cathode achieved a maximum power density of 1.24 W/cm² and showed excellent durability without degradation under a load of 1.0 A/cm² over 570 h of operation at 800 °C.     

Reversible hydrogenation/dehydrogenation performances of the Na2LiAlH6–Mg(NH2)2 system

Complex hydrides and Metal–N–H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide–hydride combined system was prepared by ball milling a mixture of Na₂LiAlH₆–Mg(NH₂)₂ in a molar ratio of 1:1.5. The hydrogen storage performances of the Na₂LiAlH₆–1.5Mg(NH₂)₂ system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ∼5.08 wt% of hydrogen, equivalent to 8.65 moles of H atoms, was desorbed from the Na₂LiAlH₆–1.5Mg(NH₂)₂ combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydrogenation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ∼4 moles of H atoms could be reversibly stored in the Na₂LiAlH₆–1.5Mg(NH₂)₂ system perhaps due to the formation of AlN and Mg₃N₂ after dehydrogenation.     

(Pr0.9La0.1)2(Ni0.74Cu0.21Nb0.05)O4+δ-Ce0.9Gd0.1O2−δ (GDC) as an active and CO2-tolerant nano-composite cathode for intermediate temperature solid oxide fuel cells

Nano composite of Ruddlesden-Popper electrocatalyst-oxygen ionic conductor, (Pr_0.9La_0.1)₂(Ni_0.74Cu_0.21Nb_0.05)O_4+δ (PLNCN)-Ce_0.9Gd_0.1O_2?δ (GDC), is developed as composite cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs) via a infiltration way. The electrochemical behavior of PLNCN-GDC nanostructured electrode is assessed with respect to infiltration loading and oxygen partial pressure. The optimized PLNCN loading can improve charge transfer dynamics for electrochemical oxygen reduction reaction, thus promoting cathode performance. Importantly, the encouraging results of single cell highlight high activity and good CO₂ tolerance of PLNCN-GDC nanostructured cathode.     

Hydrogen production aided by new (1−x)SrTi0.5Fe0.5O3–δ–xCe0.8(Sm0.8Sr0.2)0.2O2–δ (MIEC) composite membranes

In the present work, composite materials of the type (1–x)SrTi_0.5Fe_0.5O_3–δ–xCe_0.8(Sm_0.8Sr_0.2)_0.2O_2–δ (with х = 0, 0.25, 0.5, 0.75 and 1) are obtained by the two step solid state technique. Their transport properties are investigated in terms of their usage as mixed ionic-electronic conducting (MIEC) membrane materials for hydrogen production. It is found that, in reducing conditions the composites are characterized by mixed conductivity, which level is controlled by the electrical properties of the prevailing phase. Moreover, at 900 °C and pO₂ = 10⁻¹⁸ atm, total conductivity, ambipolar conductivity and oxygen permeability of composites dramatically grow (each of about 500%), when the fluorite component content x increases from 0 to 1. High-conducting and strengthened material 0.5SrTi_0.5Fe_0.5O_3–δ–0.5Ce_0.8(Sm_0.8Sr_0.2)_0.2O_2–δ is chosen for making tube shaped membranes using the tape rolling method, which are successfully applied for hydrogen production in laboratory scale. The hydrogen flux reached 0.176 ml cm⁻² min⁻¹ for x = 1, T = 900 °C and emf = 10 mV.     

Spectral Photosensitivity ofpSi—n(ZnSe)1?x?y(Si2)x(GaP)y Structures

Epitaxial layers of substitutional solid solution (ZnSe)_1−x−y(Si₂) _x (GaP) _y (0.1 ≤x≤ 1, 0≤y≤0.9) on pSi substrates were developed from a limited volume of tin solution-melt using the method of a liquid phase epitaxy. The spectral dependency of photosensitivity of the pSi—n(ZnSe)₁ −x−y (Si₂) _x (Ga.P) _y structures was studied and the peaks of photoresponses at energies of photons of 1.6, 1.66, and 1.92 eV at room temperature were discovered. It was shown that the forward-bi as regions of the volt—ampere characteristics of structures under study can be described by the power dependence of −I = I ₀ + B · V ^m with various values of a power index at various values of the voltage applied.     

Hydrogen storage properties and mechanisms of the Mg(BH4)2–NaAlH4 system

Hydrogen storage properties and mechanisms of the combined Mg(BH₄)₂–NaAlH₄ system were investigated systematically. It was found that during ball milling, the Mg(BH₄)₂–xNaAlH₄ combination converted readily to the mixture of NaBH₄ and Mg(AlH₄)₂ with a metathesis reaction. The post-milled samples exhibited an apparent discrepancy in the hydrogen desorption behavior with respect to the pristine Mg(BH₄)₂ and NaAlH₄. Approximately 9.1 wt% of hydrogen was released from the Mg(BH₄)₂–2NaAlH₄ composite milled for 24 h with an onset temperature of 101 °C, which is lowered by 105 and 139 °C than that of NaAlH₄ and Mg(BH₄)₂, respectively. At initial heating stage, Mg(AlH₄)₂ decomposed first to produce MgH₂ and Al with hydrogen release. Further elevating operation temperatures gave rise to the reaction between MgH₂ and Al and the self-decomposition of MgH₂ to release more hydrogen and form the Al_0.9Mg_0.1 solid solution and Mg. Finally, NaBH₄ reacted with Mg and partial Al_0.9Mg_0.1 to liberate all of hydrogen and yield the resultant products of MgAlB₄, Al₃Mg₂ and Na. The dehydrogenated sample could take up ∼6.5 wt% of hydrogen at 400 °C and 100 atm of hydrogen pressure through a more complicated reaction process. The hydrogenated products consisted of NaBH₄, MgH₂ and Al, indicating that the presence of Mg(AlH₄)₂ is significantly favorable for reversible hydrogen storage in NaBH₄ at moderate temperature and hydrogen pressure.     

Inorganic–organic membranes based on Nafion, [(ZrO2)·(HfO2)0.25] and [(SiO2)·(HfO2)0.28] nanoparticles. Part II: Relaxations and conductivity mechanism

Two classes of hybrid inorganic–organic proton-conducting membranes consisting of Nafion and either [(ZrO₂)·(HfO₂)_0.25] or [(SiO₂)·(HfO₂)_0.28] nanofiller are investigated to elucidate their relaxations and conductivity mechanism and are labeled [Nafion/(ZrHf)_x] and [Nafion/(SiHf)_x], respectively. The membranes are studied by dynamic mechanic analysis (DMA) and broadband electric spectroscopy (BES). The latter technique allows a determination of the direct current ionic conductivity (σ_DC) and the proton diffusion coefficient (DH₊)$\left(D_{{\text{H}}^{+}}\right)$. Pulse-field-gradient spin-echo nuclear magnetic resonance experiments (PFGSE-NMR) are carried out to determine the water self-diffusion coefficients (DH₂O)$\left(D_{{\text{H}}_2\text{O}}\right)$. DH₊$D_{{\text{H}}^{+}}$ and DH₂O$D_{{\text{H}}_2\text{O}}$ are correlated to obtain insight on the conductivity mechanism of the proposed materials. Results indicate that the nanofiller particles play a major role in the proton conduction mechanism of the proposed materials. It is demonstrated that the basic [(ZrO₂)·(HfO₂)_0.25] nanoparticles form Nafion–nanofiller dynamic cross-links with high ionic character. These cross-links improve the mechanical properties and enhance the overall proton conductivity of the membranes at low humidification levels owing to an efficient delocalization of the protons. In [Nafion/(SiHf)_x] membranes, the dynamic cross-links occur due to dipole–dipole interactions between the side groups of the Nafion host polymer and the quasi-neutral [(SiO₂)·(HfO₂)_0.28] nanoparticles. These cross-links significantly reduce the delocalization of the protons, which decreases the overall conductivity of materials.     

MIL-101(Cr)-NH2/CaCl2复合材料的热化学蓄热性能研究

将金属有机骨架MIL-101(Cr)-NH₂与CaCl₂通过浸渍的方法复合得到MIL-101(Cr)-NH₂/CaCl₂热化学蓄热复合材料。采用X射线衍射分析仪（XRD）、扫描电子显微镜（SEM）、能谱分析（EDS）、全自动比表面积及孔径分析仪以及同步热分析仪（TG-DSC）等分析了复合材料的表观形貌、盐含量、比表面积和蓄热密度等参数。结果显示,复合材料的盐含量为49%,在30℃、32%湿度下的最大吸水量为0.54 g(H₂O)/g(样品),蓄热密度达到了1 204 kJ/kg,并且在经历了17次吸附-解吸循环后,其蓄热密度仅降低了6.5%,表现出优异的循环稳定性,出色的吸附性能表明这一新型复合材料在太阳能蓄热领域具有广阔的应用前景。     

Releasing 9.6 wt% of H2 from Mg(NH2)2–3LiH–NH3BH3 through mechanochemical reaction

Ball milling the mixture of Mg(NH₂)₂, LiH and NH₃BH₃ in a molar ratio of 1:3:1 results in the direct liberation of 9.6 wt% H₂ (11 equiv. H), which is superior to binary systems such as LiH–AB (6 equiv. H), AB–Mg(NH₂)₂ (No H₂ release) and LiH–Mg(NH₂)₂ (4 equiv. H), respectively. The overall dehydrogenation is a three-step process in which LiH firstly reacts with AB to yield LiNH₂BH₃ and LiNH₂BH₃ further reacts with Mg(NH₂)₂ to form LiMgBN₃H₃. LiMgBN₃H₃ subsequently interacts with additional 2 equivalents of LiH to form Li₃BN₂ and MgNH as well as hydrogen.     

Microstructures and electrochemical hydrogen storage performances of La0.75Ce0.25Ni3.80Mn0.90Cu0.30(V0.81Fe0.19)x (x = 0–0.20) alloys

Electrochemical hydrogen storage performances of a La_0.75Ce_0.25Ni_3.80Mn_0.90Cu_0.30 alloy are improved by adding V_0.81Fe_0.19 combined with hyper-stoichiometry, and microstructures and electrochemical characteristics of La_0.75Ce_0.25Ni_3.80Mn_0.90Cu_0.30(V_0.81Fe_0.19)_x (x = 0–0.20) hydrogen storage alloys are investigated. X-ray diffraction and backscattered electron results indicate that all alloys are a LaNi₅ phase with a hexagonal CaCu₅-type structure and the lattice parameters a, c and cell volume V of the LaNi₅ phase decrease with increasing x value. The alloy electrodes keep excellent activation performance with increasing V_0.81Fe_0.19 content. Maximum discharge capacity of alloy electrodes first increases from 330.2 (x = 0) to 335.4 (x = 0.10) mAh/g, and then decreases to 328.8 mAh/g (x = 0.20) with further increasing x value. The high-rate dischargeability at the discharge current density of 1200 mA/g first increases from 67.2% (x = 0) to 76.7% (x = 0.10), and then decreases to 65.3% (x = 0.20). The cycling capacity retention rate at the 100th cycle increases from 52.3% (x = 0) to 77.9% (x = 0.20), which is mainly ascribed to the improvement of anti-pulverization.     

Fabrication of anode-supported protonic ceramic fuel cell with Ba(Zr0.85Y0.15)O3−δ–Ba(Ce0.9Y0.1)O3−δ dual-layer electrolyte

We fabricated a uniquely designed anode-supported-type protonic ceramic fuel cell (PCFC) with a dual-electrolyte layer containing BaCe_0.9Y_0.1O_3−δ (BCY) as the higher-proton-conducting phase and BaZr_0.85Y_0.15O_3−δ (BZY) as the chemically stable protecting phase. In order to overcome the poor sinterability of the BZY electrolytes, which is a critical limitation in making thin and dense dual-electrolyte layers for anode-supported PCFCs, we employed aid-assisted enhanced sintering of BZY by adding 1 mol% of CuO. We also promoted the densification of the BZY layer by utilizing the higher sinterability of BCY that is attached to the top of the BZY layer. By properly adjusting the shrinkage behaviors of both the anode substrate and the dual-electrolyte layers, we were able to fabricate a fairly dense BZY/BCY dual-layer electrolyte with a thickness of less than 20 μm. In this paper, the novel strategies used to fabricate the PCFC based on dual-electrolyte layers are reported.     

石墨烯包封Na3V2(PO4)3用作钠离子电池负极材料的电化学性能探究

具有三维网络结构的NASICON型Na₃V₂(PO₄)₃材料,由于其稳定的电压平台,较高的理论容量(117 mA·h/g),被视为一种具有良好应用前景的钠离子电池负极材料。采用溶剂热和进一步热处理的方式,获得石墨烯包封Na₃V₂(PO₄)₃的复合材料[Na₃V₂(PO₄)₃/G],有效提高了Na₃V₂(PO₄)₃的电子导电性。在0.01～3.00 V电压区间,0.2 C倍率进行测试时,Na₃V₂(PO₄)₃/G复合材料在230圈循环后,其放电比容量保持在100.9 mA·h/g,容量保持率高达68.4%,即使在5 C倍率,其放电比容量仍可达65.2 mA...     

H2 production from a single stage water–gas shift reaction over Pt/CeO2, Pt/ZrO2, and Pt/Ce(1−x)Zr(x)O2 catalysts

To develop a single stage water–gas shift reaction (WGS) catalyst for compact reformers, Pt/CeO₂, Pt/ZrO₂, and Pt/Ce_(1−x)Zr_(x)O₂ catalysts have been applied for the target reaction. The CeO₂/ZrO₂ ratio was systematically varied to optimize Pt/Ce_(1−x)Zr_(x)O₂ catalysts. Pt/CeO₂ showed the highest turnover frequency (TOF) and the lowest activation energy (E_a) among the catalysts tested in this study. It has been found that the reduction property of the catalyst is more important than the dispersion for a single stage WGS. Pt/CeO₂ catalyst also showed stable catalytic performance. Thus, Pt/CeO₂ can be a promising catalyst for a single stage WGS for compact reformers.     

Improvement of (La0.74Bi0.10Sr0.16)MnO3–Bi1.4Er0.6O3 composite cathodes for intermediate-temperature solid oxide fuel cells

Porous composite cathodes including (La_0.74Bi_0.10Sr_0.16)MnO_3−δ (LBSM) and Bi_1.4Er_0.6O₃ (ESB) were fabricated and characterized using AC impedance spectroscopy. In our earlier work, the growth and aggregation of ESB particles were found in LBSM–ESB composite cathodes. In this study, therefore, two approaches were used to restrain the growth and aggregation of ESB particles. First, the sintering temperature of the composite cathode was reduced by introducing a sintering function layer, which caused a 22% reduction in the initial polarization resistance (R), but the cathode polarization resistance decreased at a rate of 2.15 × 10⁻⁴ Ω cm² h⁻¹ at 700 °C during a period of 100 h. Second, nano-sized Gd-doped ceria powder (CGO) was added to the composite cathode system. Stability improvement was achieved at 10 vol% CGO, and the degradation rate at 700 °C was 4.01 × 10⁻⁵ Ω cm² h⁻¹ during a period of 100 h.     

Improved dehydrogenation properties of the combined Mg(BH4)2·6NH3–nNH3BH3 system

A combined strategy via mixing Mg(BH₄)₂·6NH₃ with ammonia borane (AB) is employed to improve the dehydrogenation properties of Mg(BH₄)₂·6NH₃. The combined system shows a mutual dehydrogenation improvement in terms of dehydrogenation temperature and hydrogen purity compared to the individual components. A further improved hydrogen liberation from the Mg(BH₄)₂·6NH₃–6AB is achieved with the assistance of ZnCl₂, which plays a crucial role in stabilizing the NH₃ groups and promoting the recombination of NH^δ+?HB^δ−. Specifically, the Mg(BH₄)₂·6NH₃–6AB/ZnCl₂ (with a mole ratio of 1:0.5) composite is shown to release over 7 wt.% high-pure hydrogen (>99 mol%) at 95 °C within 10 min, thereby making the combined system a promising candidate for solid hydrogen storage.     

Reversible hydrogen storage behavior of LiBH4–Mg(OH)2 composites

The dehydrogenation/hydrogenation properties of LiBH₄-xMg(OH)₂ were systematically investigated. The results show that the LiBH₄-0.3Mg(OH)₂ composite possesses optimal dehydrogenation properties: approximately 9.6 wt% of hydrogen is released via a stepwise reaction with an onset temperature of 100 °C. In the range of 100–250 °C, a chemical reaction between LiBH₄ and Mg(OH)₂ first occurs to give rise to the generation of LiMgBO₃, MgO and H₂. From 250 to 390 °C, the newly developed LiMgBO₃ reacts with LiBH₄ to form MgO, Li₃BO₃, LiH, B₂O₃ and Li₂B₁₂H₁₂ with hydrogen release. From 390 to 450 °C, the decomposition of LiBH₄ and Li₂B₁₂H₁₂ proceeds to release additional hydrogen and to form LiH and B. A further hydrogenation experiment indicates that the dehydrogenated LiBH₄-0.3Mg(OH)₂ sample can take up 4.7 wt% of hydrogen at 450 °C and 100 bar of hydrogen with good cycling stability, which is superior to the pristine LiBH₄.