The cubic nanocrystalline Li–Ti–O oxides were prepared by the solvothermal reaction of TiO2 and LiOH at 200 °C in water and aliphatic alcohols with different dielectric constants. The reaction in all solvents leads to the formation of white ternary compounds containing Li, Ti, and O. The actual Li content in the prepared materials increases with decreasing polarity of the used solvent. All prepared materials are crystalline, and their structure can be described using a spinel structural model. The structure of materials prepared at a relative dielectric constant (ϵr) value higher than 33 is characterized by Ti disorder when the Ti atoms are distributed between both types of the available octahedral sites with approximately the same probability. The tendency to form phases with Ti disorder decreases with decreasing ϵr of the solvent. All prepared materials are active toward electrochemical Li insertion. The observed specific capacity ranges between 60 and 150 mAh/g.

A combined structure/property investigation is performed to understand the catalytic effect of TiF3 additive on the absorption/desorption reactions of MgH2. It was found that both TiH2 and MgF2 phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH2–TiF3 system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF3 and its analog TiCl3, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.

Results of the mechanical alloying of binary Mg–Ti and ternary Mg–Ti–Ni mixtures using two different process control agents are reported. Both high- and low-energy milling resulted in the formation of cubic compounds. When all starting reactants had disappeared, a mixture of two face-centered cubic (fcc) phases was formed with lattice constants around 4.40 and 4.25 Å. The electrochemical hydrogen storage capacity, 450 mAh/g for (Mg0.65Ti0.35)0.95Ni0.05, was about one-third that reported for Mg–Ti thin films. This suggested that only one of the two fcc phases was active at ambient conditions. Prolonged mechanical alloying of (Mg0.60Ti0.40)0.95Ni0.05resulted in full conversion of the material into one fcc-phase with a very small crystallite size, an intermediate lattice constant (4.33 Å), and a sharply decreased storage capacity.

The in situ Raman spectroscopy technique was used to investigate the ion transport and to determine the concomitant electrochemical tuning of Fermi level in single-wall carbon nanotubes. The variation of structural bonding in a single-wall carbon nanotube bundle dipped in aqueous alkaline earth halide electrolyte such as CaCl2 with electrochemical biasing was monitored. This is because Raman scattering can detect changes in C–C bond length through radial breathing mode (RBM) at ∼184 cm−1, which varies inversely with the nanotube diameter and the G band at ∼1590 cm−1, varying with the axial bond length. Consistent reversible and substantial variation in Raman intensity of both modes was induced by electrode potential point at the fine and continuous tuning (alternatively, emptying/depleting or filling) of the specific bonding and anti-bonding molecular states. Qualitatively, the results were explained in terms of changes in the energy gap occurring between the one-dimensional van Hove singularities present in the electron density of states, possibly arising due to the alterations in the overlap integral of π bonds between the p orbitals of the adjacent carbon atoms. We estimated the extent of variation of the absolute potential of the Fermi level and overlap integral (γ0) between the nearest-neighbor carbon atoms by modeling the electrochemical potential dependence of Raman intensity. Observations also suggested that the work function of the tube becomes larger for the metallic nanotubes in contrast to the simultaneously present semiconducting nanotubes.

Crystal orientation (texture) is an important parameter in the hydrogen absorption and desorption properties of various materials. In this study, we investigate the formation of magnesium nanorod arrays with crystal orientations that are not normally observed in conventional Mg thin films. Mg nanorods are produced using an oblique angle deposition technique through a physical self-assembly process. In this study sputtering and thermal evaporation systems are utilized for the growth of Mg nanorods and thin films on silicon wafer pieces. We present a detailed X-ray diffraction and scanning electron microscopy analysis. It is discussed that under oblique incidence, evolution of crystal orientations with lower adatom mobility are promoted due to the shadowing effect.

Ambient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.

High electrochemical capacity of alkaline boride anodes is presented. The alkaline anodes based on transition metal borides can deliver exceptionally high discharge capacity. Over 3800 mAh/g discharge capacity is obtained for the commercial available vanadium diboride (VB2), much higher than the theoretical capacity of commonly used zinc metal (820 mAh/g) alkaline anode. Coupling with the super-iron cathodes, the novel Fe6+/B2- battery chemistry generates a matched electrochemical potential to the pervasive, conventional MnO2-Zn battery, but sustains a much higher electrochemical capacity.

Leptothrix discophora SP-6, a type of manganese(Mn)-oxidizing bacteria, has been known to accumulate Mn oxides from the aqueous environment and thus play a key role in microbiologically influenced corrosion by increasing the electrochemical potential of steel and other metals. Similarly, this bacterium was found to modify the surface of glassy carbon in aqueous solution and increase its potential (i.e. ennoblement). In the latter case, biomineralized Mn oxides can be used as cathodic reactants for a new generation of microbial fuel cells featuring a bio-cathode. In this preliminary study, factors affecting the biofilm formation and biomineralization processes were examined. The inflow of air into the culture medium was found essential to sustain the ennoblement of substrate electrodes. The OCP and FESEM/EDS data indicated that a smoother initial substrate surface generally led to better ennoblement. Polarizing the carbon electrode at +500mVSCE for 15 minutes was found to facilitate the ennoblement on carbon electrodes, and so did the coating with a poly(L-lysine) layer. Independent of substrate material, initial surface roughness and pretreatment, there were three parameters in the EIS equivalent circuit that correlated well with the OCP indicating the level of ennoblement by L. discophora SP-6, i.e., electrolyte resistance, double-layer capacitance, and low-frequencies capacitance. These fascinating findings merit further investigation as they may shed light on the fundamental bacteria/substrate interactions and help advance the knowledge base needed for the engineering applications.

With its ultra-large specific surface area, a nanoporous material is an ideal, yet relatively unexplored, platform for accepting or actuating liquids, with potential performance gains for energy dissipation and output typical of disruptive technologies. Our experimental and theoretical results indicate either dramatically improved performance or unique combinations of properties and capabilities not attainable in conventional materials, which make the novel nanoporous structures studied herein very attractive as advanced protective intelligent systems.

The point of view taken here is that systems analysis is a kind of learning process, not data gathering, not decision making, but the production and effective communication of arguments relevant in a particular context. This idea, that the intended application of the result of an assessment has consequences for methodological choices, is beginning to spread in the LCA research community. One problem is that standard LCA methodology is developed to answer questions about environmental impacts of the current production and use of one unit of a product or minor product or process changes. When this methodology, unchanged, is used to provide answers to questions about strategic technology choice, i.e. not decisions that aim at improving a process within an existing technological environment, but with the long-term goal of changing large-scale technological systems, the result could be of little value or misleading. In many cases, LCAs produce more noise than knowledge. This observation seems to be of particular importance for LCAs of energy technologies and for how energy use is treated in all kinds of LCAs. Here, it is suggested that a better understanding of some critical methodological issues related to time, universality, cause-effect relationships, technical maturity and system innovation, could result in better studies that reveal fundamental environmental issues related to the objects of study and reduce the noise from irrelevant information. Examples are given from the technology fields of solar cells, fuel cells, batteries, renewable transport fuels and carbon nanoparticles.

In this paper, we demonstrated that Lead Zirconate Titanate (PZT) nanofibers can be used to harvest energy from dynamic loading and mechanical vibration. PZT nanofibers were fabricated by electrospinning process. SEM image of PZT nanofibers has shown that the average diameter of these fibers is about 150nm, which can be tuned from 50nm to 200 nm by varying the composition and viscosity of the precursor for electrospining. Titanium substrate with ZrO2 layer was used to collect the PZT nanofibers for the demonstration of energy harvesting from dynamic loading. The largest output voltage is 170mV under 0.5% strain; the frequency of the output voltage is the same as that of the input loading. Silicon substrate with trenches was used to collect the nanofibers for energy harvesting from vibration. The output voltage generated from 150Hz sinusoid vibration source has peak voltages of 64.9mV and -95.9mV. These experimental results suggest that PZT nanofibers have great potentials for energy harvesting from environments and being used as nanogenerators. Further study is under the way to optimize the design and improve the efficiency.

Since the publication of the 2003 report on Basic Energy Needs for the Hydrogen Economy, many important advances in hydrogen research have occurred, a cadre of enthusiastic researchers has entered the field with great interest shown by students, and private industry has made significant commitment to this technology and investment in its development worldwide. Concurrently, other energy technologies have made major strides forward. These technologies must be evaluated for their scalability, usability, cost and life cycle footprint on the environment. This overview discusses these topics and looks toward the role for the hydrogen economy into our energy future.

In an effort to develop reversible metallic borohydrides with high hydrogen storage capacities and low dehydriding temperature, modifications to LiBH4 with metal halides TiCl3 have been conducted. Adding TiCl3 to LiBH4 effectively reduced the dehydriding temperature through an ion exchange interaction by producing instable transition metal borohydrides and lithium salts. The material LiBH4+0.1TiCl3 desorbed 3.5wt% and 8.5wt% hydrogen at 150°C and 450°C respectively. Subsequent re-absorption of 6wt% hydrogen at 500°C and 70 bars was observed. The XRD analysis of the rehydrided samples confirmed the partial reformation of LiBH4. However, adding more TiCl3 made material more volatile and irreversible. TGA-RGA analyses indicated diborane evolution during dehydrogenation resulting in unrecoverable capacity loss and irreversibility. TiCl3 reduced LiBH4 stability and also made material irreversible.

Efficient storage of hydrogen for use in fuel cell-powered vehicles is a challenge that is being addressed in different ways, including adsorptive, compressive, and liquid storage approaches. In this paper we report on adsorptive storage in nanoporous carbon fibers in which palladium is incorporated prior to spinning and carbonization/activation of the fibers. Nanoparticles of Pd, when dispersed in activated carbon fibers (ACF), enhance the hydrogen storage capacity of ACF. The adsorption capacity of Pd-ACF increases with increasing temperature below 0.4 bar, and the trend reverses when the pressure increases. To understand the cause for such behavior, hydrogen uptake properties of Pd with different degrees of Pd-carbon contact (Pd deposited on carbon surface and Pd embedded in carbon matrix) are compared with Pd-sponge using in situ XRD under various hydrogen partial pressures (<10 bar).

Rietveld refinement and profile analysis of diffraction patterns does not show any significant changes in carbon structure even under 10 bar H2. Pd forms β PdH0.67 under 10 bar H2, which transforms to α PdH0.02 as the hydrogen partial pressure is decreased. However, the equilibrium pressure of transition (corresponding to a 1:1 ratio of α and β phases) increases with increasing the extent of Pd-carbon contact. This pressure is higher for Pd embedded in carbon than for Pd deposited on carbon surface. Both these Pd-carbon materials have higher H2 desorption pressure than pure Pd, indicating that carbon “pumps out” hydrogen from PdHx and the pumping power depends on the extent of Pd-carbon contact. These results support the spillover mechanism (dissociative adsorption of H2 followed by surface diffusion of atomic H).

Nanostructured materials and nanocomposites have inspired many structural and functional applications in recent time. In the last decade, energy-storage devices have employed electrode materials in form of nanomaterials/nanocomposites to yield promising electrochemical performance. The current paper throws light on the application of nanostructured pristine activated carbons as well as chemically modified carbon-halide nanocomposites in practical electrochemical supercapacitors. Pristine activated carbons have been mechanochemically modified via high-energy milling and iodine doping to produce carbon-halide nanocomposites. A significant change in existing physical and electrochemical properties has been marked by introduction of iodine into carbon and the subsequent formation of nanocomposites. The effect of halides and nanoscale morphology is discussed using X-ray, Raman spectroscopy, DSC, BET analysis and electrochemical testing.

The emergence of a Hydrogen Economy will require the development of new media capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides, where hydrogen is chemically bonded to the metal atoms in the bulk, offer some hope of overcoming the challenges associated with hydrogen storage. Many of the more promising hydrogen materials are tailored to meet the unique demands of a low temperature automotive fuel cell and are therefore either entirely new (e.g. in structural or chemical composition) or in some new form (e.g. morphology, crystallite size, catalysts). This proceeding presents an overview of some of the challenges associated with metal hydride hydrogen storage and a few new approaches being investigated to address these challenges.

Metal hydrides and amides are potential candidate materials for hydrogen storage. Lithium- and magnesium-based material systems are among the most promising materials owing to their high hydrogen contents. In the present work, we investigated hydrogenation/dehydrogenation reactions of a binary nitride, LiMgN. LiMgN can be formed by a reaction of MgH2 with LiNH2 in 1:1 ratio. The reaction also releases approximately ∼ 8.1 wt% H2 (theoretical value is 8.2 wt%) between 160 and 220 °C. The reaction product LiMgN can be rehydrogenated by reacting with H2 under 2000 psi of hydrogen pressure and 160 °C with small amount of TiCl3 doping. TGA results showed that about 8.0 wt% of hydrogen was stored in TiCl3-doped LiMgN during the hydrogenation process. The reversible hydrogenation and dehydrogenation mechanisms involving LiMgN and H2 are discussed.

The solubility of H in the solid solution phase of the Ti35Cr47V18 alloy has been investigated at high and low temperature. The Sieverts law has been found to hold for 808 K≤T≤1204 K and fail for 302 K≤T≤335 K. For H contents nH ≤0.07 (nH=H/Me) the partial molar enthalpy and partial non-configurational entropy at high temperature are:

On heating the material under H2 gas pressures lower than 0.1 MPa H absorption only occurs above 700 K. Below this temperature, surface oxide films prevent H uptake. Thermal decomposition spectroscopy of the α phase carried out for nH≤0.24 exhibits a single peak whose temperature increases with decreasing nH owing to selective occupancy by H of energetically non-degenerate interstitial sites.

Recent progresses on two series of light-element hydrides are briefly explained from the viewpoint of 1) prevention/suppression of gas-phase ammonia from mixtures of Mg(NH2)2 and LiH, and also 2) occurrences of reversible dehydriding and rehydriding reactions in NaMgH3.

Mass produced multi-walled carbon nanotubes have examined their feasibility as an electrode for supercapacitors. Activation behavior of MWNTs with different diameter is quite different. In this study, the effect by diameter on KOH activation of MWNTs are confirmed.