Ionic transport and battery characterization studies on NaINa2OB2O3 ternary glassy system

Glasses in the ternary system xNaI-yNa₂O-[100−(x+y)]B₂O₃ prepared by a melt quenching method are characterized by using different experimental techniques such as X-ray diffraction, ionic transference number and conductivity. The conductivity is found to vary in a non-linear manner with change in the NaI/Na₂O ratio. The highest conductivity glass composition is used as an electrolyte in the fabrication of a solid-state electrochemical cell. A decomposition potential of 2.5 V is determined for the electrolyte. The discharge chracteristics of the cell are investigated at ambient temperature and various cell parameters are determined. The open-circuit voltage and short-circuit current of the cell are 2.7 V and 1600 μA, respectively.     

Ionic (O2−, H+) transport in novel Zn-doped perovskite LaInO3

For the first time the LaIn_1-xZn_xO_3-1/2x samples was synthesized via solid-state reaction method. The Zn²⁺−doping effect on the B-site of LaInO₃ on structure, water uptake and electrical properties was investigated. The results show that Zn²⁺ is good alternative to alkaline earth metals. The Zn-doping decreases the sintered temperature and makes it possible to obtain high-density ceramics. The substitution increases the conductivity by ∼2 orders of magnitude. Below ∼500 °C the phases exhibit the dominant oxygen-ionic transport (dry atmosphere), and the dominant protonic transport below 600 °C (wet atmosphere). The obtained results suggest the prospects for using these materials in the Hydrogen Energy field. A new concept of the ability of perovskite phases LaBO₃ to incorporate water has been proposed. In addition to the presence of oxygen vacancies, their size, which depends on the B-cation nature, is of decisive importance in the hydration process and the formation of proton conductivity.     

Conductivity and parametric studies of a (PEO+(glass)(15Na2O–15NaF–70B2O3)) cell

Ion conducting polymer electrolyte films based on poly(ethylene oxide) (PEO) complexed with a glass (15Na₂O–15NaF–70B₂O₃) are prepared by a solution—cast technique. The complexation of the glass with PEO is confirmed by X-ray diffraction analysis. DC conductivity in the temperature range 303–373 K and transference number measurements are performed in order to investigate the charge transport in the polymer electrolyte system. The conductivity of the (PEO+glass) electrolyte is about 10⁴ times larger than that of pure PEO at room temperature. The transference number data show that the charge transport in this polymer electrolyte system is predominantly due to ions. Using these polymer electrolytes, solid-state electrochemical cells are fabricated. Various parameters associated with these cells are evaluated and compared with those of other reported cells.     

Alkali insertion within NiONi electrode in contact with molten Li2CO3K2CO3 and Li2CO3Na2CO3K2CO3 at 650°C

Lithium, sodium and potassium species have been analysed by different spectroscopic techniques in the NiO layer recovering nickel cathode used in the state-of-the-art molten carbonate fuel cell. The nickel electrode was previously oxidized in lithium-containing carbonate electrolytes, Li₂CO₃K₂CO₃ and Li₂C0₃Na₂CO₃K₂CO₃ at 650°C. Similarly to the well-known case of lithium, it has been shown that the presence of sodium and potassium cations could be associated to their insertion in the NiO lattice.     

Synthesis and characterization of lithium aluminum-doped spinel (LiAlxMn2−xO4) for lithium secondary battery

LiAl_xMn_2−xO₄ has been synthesized using various aluminum starting materials, such as Al(NO₃)₃, Al(OH)₃, AlF₃ and Al₂O₃ at 600–800°C for 20 h in air or oxygen atmosphere. A melt-impregnation method was used to synthesize Al-doped spinel with good battery performance in this research. The Al-doped content and the intensity ratio of (3 1 1)/(4 0 0) peaks can be important parameters in synthesizing Al-doped spinel which satisfies the requirements of high discharge capacity and good cycleability at the same time. The decrease in Mn³⁺ ion by Al substitution induces a high average oxidation state of Mn ion in the LiAl_xMn_2−xO₄ material. The electrochemical behavior of all samples was studied in Li/LiPF₆-EC/DMC (1:2 by volume)/LiAl_xMn_2−xO₄ cells. Especially, the initial and last discharge capacity of LiAl_0.09Mn_1.97O₄ using LiOH, Mn₃O₄ and Al(OH)₃ complex were 128.7 and 115.5 mAh/g after 100 cycles. The Al substitution in LiMn₂O₄ was an excellent method of enhancing the cycleability of stoichiometric spinel during electrochemical cycling.     

Preparation and characterization of LiNiO2 synthesized from Ni(OH)2 and LiOH·H2O

Synthesis of LiNiO₂ by heat-treatment of Li(OH)·H₂O and Ni(OH)₂ is reported. The influence of synthesis conditions on the electrochemical performance of the resulting LiNiO₂ is investigated. Thermal analysis of the synthesis process shows that LiNiO₂ formation proceeds through the transformation of Ni(OH)₂ to a layered compound Ni_1−x(OH)_2−x, followed by solid reaction with LiOH. The most favorable condition is heating a mixture of Li(OH)·H₂O and Ni(OH)₂ at 650°C, and then at 720°C in oxygen. The resulting LiNiO₂ exhibits a considerably high discharge capacity of 145 mA h g⁻¹ and a sufficiently long cycle-life when cycled over a lithium composition range of 0.2≤x≤0.65.     

Isotopic effects and dehydriding kinetics in the Mg2NiH2(D2) system

Measurements of the equilibrium isotopic effects in the Mg₂Ni-hydrogen (deuterium) system are reported. The values of the enthalpies of transformation for the absorption and desorption reactions are critically compared to literature data. The dehydriding kinetics are studied, concluding that the reaction progresses by a nucleation and growth mechanism, with the hydrogen (deuterium) diffusion in the α-phase as a rate limiting process at high thermodynamic driving forces. The role of the hydride-solid solution (β/α) interface increases as the pressure approaches a value P_o, lower than the equilibrium dissociation pressure. At pressure above this P_o, the process becomes interface-controlled and an incubation time is observed in the dehydriding reactions. The activation energy for the hydrogen diffusion in α-phase has been tentatively evaluated from the kinetic data and compared to that reported in literature.     

Effect of plastic deformation on ionic conduction in pure AgI and AgIAl2O3 composite solid electrolytes

The ionic conductivities of pure silver iodide and silver iodide-(10–40 mol%) alumina composites used as solid electrolytes are determined at room temperature by a.c. impedance spectroscopy as a function of compression pressure and annealing temperature. The ionic conductivities of both the pure and the composite silver iodide specimens increase with increasing compression pressure. This suggests that structural defects acting as conduction paths are generated in abundance by the plastic deformation. The mechanical strength of the as-deformed pure silver iodide specimen is decreased drastically by annealing at 413 K, whereas that of the as-deformed composite specimens remains virtually, unchanged. This indicates that the deformation-induced defects are present largely as dislocations. The ionic conductivity of the as-deformed pure silver iodide specimen determined during annealing at 323 K decreases with annealing time, whereas the conductivities of the as-deformed composite specimens are practically unchanged. It is concluded that the removal of the deformation-induced dislocations during annealing is impeded by dispersed alumina particles.     

Solvothermal synthesis,nanostructural characterization and gas cryo-adsorption studies in a metal–organic framework (IRMOF-1) material

A nanoporous metal–organic framework material, exhibiting an IRMOF-1 type crystalline structure, was prepared by following a direct solvothermal synthesis approach, using zinc nitrate and terephthalic acid as precursors and dimethylformamide as solvent, combined with supercritical CO₂ activation and vacuum outgassing procedures. A series of advanced characterization methods were employed, including scanning electron microscopy, Fourier-transform infrared radiation spectroscopy and X-ray diffraction, in order to study the morphology, surface chemistry and structure of the IRMOF-1 material directly upon its synthesis. Porosity properties, such as Brunauer–Emmet–Teller (BET) specific area (～520 m²/g) and micropore volume (～0.2 cm³/g), were calculated for the activated sample based on N₂ gas sorption data collected at 77 K. The H₂ storage performance was preliminary assessed by low-pressure (0–1 bar) H₂ gas adsorption and desorption measurements at 77 K. The activated IRMOF-1 material of this study demonstrated a fully reversible H₂ sorption behavior combined with an adequate gravimetric H₂ uptake relative to its BET specific area, thus achieving a value of ～1 wt.% under close-to-atmospheric pressure conditions.     

Achievement of excellent hydrogen sorption through swift hydrogen transport in 1:2 Mg(NH2)2–LiH catalyzed by Li4BH4(NH2)3and carbon nanostructures

The present studies deal with the catalytic character of carbon nanostructure (Graphene (Gr) and single-wall carbon nanotubes (SWNTs), and their composite versions) on the hydrogen sorption behavior of 1:2 Mg(NH₂)₂–LiH/Li₄BH₄(NH₂)₃. The inclusion of an optimal quantity of 2 wt% SWNTs in Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ resulted in superior hydrogen sorption over 2 wt% Gr and 2 wt% of (Gr and SWNT) composite. The onset desorption temperature for SWNTs catalyzed Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ is 108 °C which is 32 °C, 44 °C lower compared to Gr catalyzed Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ and uncatalyzed Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ respectively. The de/re-hydrogenation kinetics of the SWNT catalyzed sample has been found to be 4.02 wt% and 4.63 wt% within 15min at 170 °C and 7 MPa H₂ pressure, correspondingly. The activation energy for SWNT catalyzed Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ has been found to be 69.75 kJ/mol. The SWNT catalyzed Mg(NH₂)₂–2LiH/Li₄BH₄(NH₂)₃ shows good cyclic stability (almost no degradation) up to 10 cycles. The better hydrogen sorption for SWNTs is attributed to the ballistic transport of hydrogen atoms within and across the amide/hydride matrix. In contrast, Gr sheets agglomerate, which adversely affects hydrogen sorption from Gr and Gr+SWNT composites. A hydrogen sorption mechanism has been proposed based on structural, microstructural, Fourier-transform infrared spectroscopy, and Raman characterization results.     

Preparation and characterization of high temperature Sr(Ce0.6Zr0.4)0.9Y0.1O3-δ/YBaCo2O5+δ mixed proton-electron composite membrane

In this study, the various Sr(Ce_0.6Zr_0.4)_0.9Y_0.1O_3-δ/YBaCo₂O_5+δ (SCZY/YBCO) composite ceramic membranes were prepared by sintering at different temperatures and used as proton membranes for hydrogen permeation. SCZY and YBCO powders were prepared by the citrate-ethylenediaminetetraacetic acid sol-gel process and solid-state reaction method, respectively. The chemical reaction, structure, morphology, thermal expansion, and electrical conductivity of SCZY/YBCO were investigated through X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermal mechanical analyzer (TMA) and direct current four-probe method. The relative sintered density of SCZY/YBCO membrane sintered at 1250 °C was as high as 99.5%. The conductivity of the SCZY/YBCO increased with the sintering temperature. The SCZY/YBCO sample sintered at 1250 °C exhibited the highest conductivity of 13.44 S/cm at 800 °C. The H₂ permeability of the SCZY/YBCO membrane was 3.83 mL min⁻¹ cm⁻², much higher than that of SCZY at 800 °C (1.37 mL min⁻¹ cm⁻²).     

PdO/ZrO2 engineered (La0.8Sr0.2)0.95MnO3-δ-(Y2O3)0.08(ZrO2)0.92 cathode for use in intermediate temperature solid oxide fuel cells

To enhance the electrochemical performance of (La_0.8Sr_0.2)_0.95MnO_3-δ-8 mol. % Y₂O₃ stabilized ZrO₂ (LSM-YSZ) cathode at reduced temperatures, PdO and ZrO₂ (Pd/Zr = 0.8/0.2) are co-infiltrated into the LSM-YSZ scaffold. Such prepared composite cathode is investigated at temperatures between 600 and 750 °C and cathodic current densities of 400 and 800 mA cm^?2. It is observed that PdO particles are uniformly deposited on the surface of the LSM-YSZ and surrounded by nano-sized ZrO₂ particles. This distinctive microstructure possesses improved thermal stability under current at 750 °C due to the hindering effect of ZrO₂ on the agglomeration and growth of PdO particles. As a result, the electrocatalytic activity of the cathode for oxygen reduction reaction (ORR) is greatly enhanced due to presence of the self-limited PdO particles. At open circuit voltage, the initial polarization resistance decreases from 1.68 to 0.40 Ω cm² as temperature increases from 600 to 750 °C; and the polarization resistance is fully stabilized at the level of 0.36 and 0.34 Ω cm², respectively, after current polarization at 750 °C under 400 and 800 mA cm^?2 for less than 200 h.     

Pechini sol-gel synthesis of Ni(II) doped LiMnBO3/Li2MnO3/Li2B2O4 nano-photocatalyst under UV–Vis irradiation

NiO doped LiMnBO₃/Li₂MnO₃/Li₂B₂O₄ (LMBO) nanoscale composites were prepared through sol-gel (Pechini-type) route using the combination of Ni, Mn and Li cations with Ethylenediaminetetraacetic acid (EDTA) as a chelating operator. By changing molar ratios of M: ethylene glycol: EDTA can control appearance properties of nanocomposites. Analyses of FT-IR, XRD and EDX were accomplished aimed at the approval of crystalline and structural features. Also, in order to investigation of morphology, scanning and transmission electron microscopy images were taken. The prepared nanocomposite with 1:1:1 M ratio in presence of EDTA has optimized size and morphology. Optical property and band-gap energy of NiO doped LMBO ternary nanocomposite computed by UV–Vis information is 3.1 eV. The magnetic character of the prepared nanocomposite investigated through VSM illustrates ferromagnetic performance. Besides, photodegradation activities of pristine and NiO doped LMBO ternary nanocomposites were examined by different lights on two diverse dyes of malachite green and acid red 88. Some operative factors including radiation, pollutant and nanoscale composite sort were considered in order to optimize elimination of water contaminant dyes. In both cationic and anionic dyes, NiO doped LMBO ternary nanocomposite has better performance than LMBO nanocomposite.     

Comment on “3D squeezed flow of γAl2O3–H2O and γAl2O3–C2H6O2 nanofluids: A numerical study,Int. J. Hydrogen Energy 42 (2017) 24620–24633”

The present comment concerns the improvement of the similarity energy equation that has been written incorrectly in the article by Khan et al. [1]. In this note, we derive its correct form and show that such a mistake may affect the results.     

Processing and characterization of novel Ce0.8Sm0.1Bi0.1O2-δ-BaCe0.8Sm0.1Bi0.1O3-δ (BiSDC-BCSBi) composite electrolytes for intermediate-temperature solid oxide fuel cells

Ce_0.8Sm_0.1Bi_0.1O_2-δ-BaCe_0.8Sm_0.1Bi_0.1O_3-δ (BiSDC-BCSBi) composites are fabricated as novel electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Both dramatically enhanced sinterability and electrical performance are obtained due to the Bi doping. BiSDC-BCSBi composites are densified at as low as 1200 °C, allowing a decrease of 350 °C compared with Ce_0.8Sm_0.2O_2-δ-BaCe_0.8Sm_0.2O_3-δ (SDC-BCS) composites. The optimal electrical conductivity of BiSDC-BCSBi electrolytes measured at 600 °C in humid air reaches up to 27.97 mS cm^?1, almost 6 times higher than that of SDC-BCS electrolytes (3.91 mS cm^?1 in humid air), which is mainly attributed to their lower sintering temperature, more uniform microstructure, larger tensile strains, and higher concentrations of O–H groups and oxygen vacancies. The electrolyte-supported single cell with BiSDC-BCSBi electrolyte displays a peak power density of 397 mW cm^?2 at 600 °C using humid hydrogen as fuel and ambient air as oxidant. These results imply that BiSDC-BCSBi composites have a great application prospect for IT-SOFCs.     

Combined steam and CO2 reforming of methane (CSCRM) over Ni–Pd/Al2O3 catalyst for syngas formation

In order to syngas formation, combined steam and carbon dioxide reforming of methane (CSCRM) used in the presence of Ni–Pd/Al₂O₃ catalysts, which were synthesized by the sol-gel method. Al₂O₃ supported Ni–Pd catalyst exhibited the appropriate surface area of 176.2 m²/g and high dispersion of NiO phase with an average crystallite size of 11 nm, which was detected on catalyst surface utilizing transmission electron microscopy (TEM). The influence of three independent operating parameters including reaction temperature in the range of 500–1000 °C; (CO₂ + H₂O)/CH₄ ratio, in the range of 1–3 and CO₂/H₂O ratio; in the range of 1–3, were investigated on the responses (i.e., CH₄ conversion, H₂ yield, CO yield, amount of coke formation on the catalyst surface and H₂/CO ratio) in CSCRM by using response surface methodology–central composite design (RSM-CCD) method. The obtained results from ANOVA and the proposed quadratic models could fine forecast the responses. It was seen that the total methane conversion and CO yield was almost accessible at temperatures higher than 850 °C. Moreover, the CO₂/H₂O ratio exhibited no significant effect on the CH₄ conversion, H₂ yield and CO yield of Ni–Pd/Al₂O₃ catalysts in CSCRM reaction. However, the high CO₂/H₂O ratio in inlet feed led to the syngas formation with a low H₂/CO ratio. The results revealed that lower CO₂/H₂O ratio and higher temperature as well as higher (CO₂ + H₂O)/CH₄ ratio help to decrease the coke formation.     

Rayleigh–Bénard convection of Al2O3/water nanofluids in a cavity considering sedimentation,thermophoresis, and Brownian motion

This paper aims to investigate the Rayleigh–Bénard convection of Al₂O₃/water nanofluids in a cavity considering the sedimentation, thermophoresis, and Brownian motion. For this purpose, a numerical simulation is carried out using finite volume method to obtain the flow patterns and heat transfer characteristics of nanofluid flow inside the cavity. The results are presented for volume fractions up to 4%, Rayleigh numbers between 10⁴ and 8 × 10⁴ where the temperature difference between top and bottom walls is between 2 and 10 °C. To validate the numerical solution, comparisons are made between the numerical results and experimental data available in the literature. The comparisons unfold that the results of numerical work are in a good agreement with the previous experimental results.