Search

Nanopowder of Ce 0.8 Tb 0.2 O 2− δ , a fluorite-type mixed conductor stable in wide p (O 2 ) range, was successfully synthesised by the hydrothermal method. Dense ceramics sintered at relatively low temperatures (900 and 1200 °C), by employing minor additions of cobalt oxide sintering additive (2 mol%), were compared to those sintered at 1500 °C without additives. The effect of the sintering temperature on oxygen transport was analysed in O 2 and N 2 atmospheres. Oxide-ion transference numbers were determined by the modified electromotive force (EMF) method under oxygen/air and nitrogen/air gradients, showing positive temperature dependencies for all sintering temperatures. The partial ionic and electronic conductivities, calculated from the transference numbers and total conductivity, both increase with cobalt additions. A detailed transmission electron microscopy (TEM) study shows a grain boundary location of the cobalt sintering additive at the lowest sintering temperature, 900 °C. On increasing sintering temperature the grain-boundary concentration of cobalt is depleted, leading to the presence of segregated grains of cobalt oxide. This factor is shown to be highly relevant with respect to measured oxygen permeation fluxes. Ce 0.8 Tb 0.2 O 2− δ ceramics sintered at 900 °C show significantly higher oxygen permeation, related to improved surface exchange due to the grain-boundary enrichment of cobalt and larger grain-boundary area. [ABSTRACT FROM AUTHOR]

A novel nanocomposite (0.2TiO 2 + AC) with two promising applications is demonstrated, (i) as an additive for promoting hydrogen storage in magnesium hydride, (ii) as an active electrode material for hosting lithium in Li ion batteries (surface area of activated carbon (AC): 491 m2/g, pore volume: 0.252 cc/g, size of TiO 2 particles: 20–30 nm). Transmission electron microscopy study provides evidence that well dispersed TiO 2 nanoparticles are enclosed by amorphous carbon nets. A thermogravimetry-differential scanning calorimetry (TG-DSC) study proves that the nanocomposite is thermally stable up to ∼400 °C. Volumetric hydrogen storage tests and DSC studies further prove that a 3 wt% of 0.2TiO 2 +AC nanocomposite as additive not only lowers the dehydrogenation temperature of MgH 2 over 100 °C but also maintains the performance consistency. Moreover, as a working electrode for Li ion battery, 0.2TiO 2 +AC offers a reversible capacity of 400 mAh/g at the charge/discharge rate of 0.1C and consistent stability up to 43 cycles with the capacity retention of 160 mAh/g at 0.4C. Such cost effective-high performance materials with applications in two promising areas of energy storage are highly desired for progressing towards sustainable energy development. [Display omitted] • Pores of activated carbon filled with titania is prepared for energy storage. • The TiO 2 /AC composite as an additive promotes hydrogen storage in Mg-H system. • The same material is also found to be a useful Li host material for Li ion battery. • TiO 2 /AC offers appreciable cycle sustainability for both H storage and Li storage systems. • Such cost-effective materials with multiple benefits are highly desired for energy security. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells are a promising technology for energy conversion and chemical synthesis in the intermediate temperature range (400–600 °C). Nevertheless, a major restriction to their wider implementation concerns their relatively high cathode polarisation resistance that can become performance limiting as working temperatures decrease. As potential new cathode materials, high order nickelates can be attractive candidates as they exhibit high electrical conductivities at lower temperatures due to their metallic behaviour. In the current work, we investigate the performance of La 4 Ni 3 O 10±δ and La 4 Ni 3 O 10±δ –BaCe 0.9 Y 0.1 O 3-δ composite cathodes, deposited on a BaCe 0.9 Y 0.1 O 3-δ (BCY10), proton-conducting electrolyte in the temperature range 350–550 °C. The study is performed in symmetrical cell configuration to permit separation of the electrode performance from the overall cell behaviour. For such experiments, possible internal short-circuiting of the electrolyte in oxidising conditions can arise from the presence of p-type electronic conductivity in the BCY10 electrolyte, causing underestimation of measured polarisation resistances. The current work corrects for such factors by knowledge of the transference numbers of the BCY10 electrolyte and the use of a parallel short-circuiting resistor in the equivalent circuit model. The results underscore that the cathode characteristics are highly dependent on the electronic leakage, especially at higher temperatures, and that suitable correction of data is imperative before discussion. Corrected values for polarisation resistance in wet O 2 reveal the composite cathode shows an improvement of total polarisation resistance by a factor of 1.5. The analysis on the oxygen reduction reaction mechanism allows the rate-limiting processes between the electrodes to be differentiated, with the low-frequency term, corresponding to surface processes, being the dominant polarisation resistance and the most improved on formation of the composite. Overall performance analysis indicates that the results from this work are in line with some of the best cathodes currently reported. • Electronic short-circuiting in oxidising conditions with increasing temperature. • Equivalent circuit modelling allows for correction of the electronic leakage. • LNO-BCY10 cathode shows decreased R p in comparison to that of pure LNO. • LNO-BCY10 cathode shows one of the best performances among PCFC cathodes. [ABSTRACT FROM AUTHOR]

• Nanorod shaped MIL-88B(Fe) and MIL-100(Fe) were tested as anodes for li ion batteries. • Overall, MIL-88B(Fe) exhibits higher capacity and lesser resistance than MIL-100(Fe). • Degradation and loss of Fe over cycles is found only in the MIL-88B(Fe) based electrode. • Li diffusion remains unaffected despite the degradation issue in MIL-88B(Fe). Two Fe based metal organic framework (MOF) nanorod structures, MIL-88B(Fe) and MIL-100(Fe), were synthesized and their performance as working electrodes for Li ion half-cell batteries was evaluated under identical testing conditions. It was found that MIL-88B(Fe) provides a charge / discharge capacity of 468 mAh/g at the current density of 100 mA/g, which is over 3 times higher as compared to that of MIL-100(Fe) under the same conditions. Nevertheless, after an impressive charge / discharge capacity in the first few cycles, a slow capacity degradation was noticed in the case of the MIL-88B(Fe) material. Energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy results suggest that capacity degradation may be due to strained metal coordination in the MIL-88B(Fe) network. In contrast, despite moderate charge / discharge capacity such issues are identified to be minimal in the case of MIL-100(Fe). Electrochemical impedance spectroscopy (EIS) analyses suggest that ohmic and polarization resistance are smaller for MIL-88B(Fe) as compared to MIL-100(Fe) (both cycle 1 and 100). This makes MIL-88B(Fe) an attractive anode over MIL-100(Fe) for Li ion batteries, but stability issues remain a concern with MIL-88(B)Fe. [ABSTRACT FROM AUTHOR]

• Mixtures of antimony and lead are studied against their oxidation behavior. • A robust test setup avoids the necessity of precious metals as current collectors. • The polarization resistance and the degree of melt segregation are correlated. Liquid metals have emerged as potential materials for fuel cell and battery applications due to their suitable redox potentials, fast redox kinetics, and/or active participation in electrode reactions. In this work, we study the electrochemical oxidation behavior of antimony-lead melts by the use of a robust, yttrium-stabilized zirconia based, test setup that can avoid the necessity for the use of precious metals as current collectors. Impedance spectroscopy results obtained at 700°C as a function of applied anodic polarization reveal the presence of two main contributions: an interfacial resistance, occurring at high-frequencies, related to the transference of oxygen-ions between the electrolyte and the anode melt and a low-frequency contribution, related to the diffusion of oxidized species within the bulk of the melt. These electrode mechanisms were followed as a function of the extent of melt oxidation, with suggested links made to the degree of melt segregation supported by SEM and XRD analyses. [ABSTRACT FROM AUTHOR]

• A new Li-ion anode chemistry based MgH 2 -added TiO 2 is reported. • The half-cell shows higher lithium diffusion coefficient than pure TiO 2. • The capacity retention reaches 300 mA h g−1 at 0.1C. This work explores the electrochemical performance of a 10 wt.% MgH 2 added titania anode for Li-ion half-cell batteries. We used a distribution function of relaxation times (DFRT) analysis to quantify the sources of polarisation losses from the impedance data. We observed a notable increase in both ohmic and polarisation resistance terms for the TiO 2 +10 wt.% MgH 2 compared to the standard titania anode. Nonetheless, the modified electrode showed a significantly higher lithium diffusion coefficient than pure TiO 2 , with capacity retention reaching 300 mA h g−1 at 0.1C. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) reveals a higher surface coverage by secondary surface(s) upon lithium insertion for MgH 2 added titania. Scanning Electron Microscopy (SEM) and atomic force microscopy (AFM) studies provide indirect evidence that different nanodomains with different conducting properties evolve at the anode side upon making various charging/discharging cycles. [ABSTRACT FROM AUTHOR]