Hydrogen is recognized as a potential, extremely interesting energy carrier system, which can facilitate efficient utilization of unevenly distributed renewable energy. A major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular, for mobile applications. Here we report on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. LiBH4 and MgH2 nanoparticles are embedded in a nanoporous carbon aerogel scaffold with pore size Dmax approximately 21 nm and react during release of hydrogen and form MgB2. The hydrogen desorption kinetics is significantly improved compared to bulk conditions, and the nanoconfined system has a high degree of reversibility and stability and possibly also improved thermodynamic properties. This new scheme of nanoconfined chemistry may have a wide range of interesting applications in the future, for example, within the merging area of chemical storage of renewable energy.

A five percent by weight of carboxylic acid terminated perfluoropolyether hybrid with silica (Krytox-Silica) in Nafion composite polymer was used in the modification of a polymer electrolyte fuel cell membrane in order to improve its efficiency at high operating temperatures. Molecular dynamics (MD) simulations were carried out in order to understand the microscopic properties of two systems, Krytox-Silica in Nafion and pure Nafion. A model of five percent Krytox-Silica in a Nafion composite polymer consisting of 15 Nafion side chains, 15 hydronium ions and one of Krytox-Silica was used. In another system, pure Nafion was modeled without Krytox-Silica. Models with various amounts of water molecules and temperatures were simulated to study the water content and temperature effects. The results were in good agreement with the experiments and could be used to describe the application of Krytox-Silica–Nafion composite at high temperatures. The effect of the amount of water molecules on the diffusion coefficient or proton conductivity showed more deviations between 5% wt of Krytox-Silica–Nafion composite and pure Nafion system at lower water content (or higher temperature) than at high water content (or low temperature). According to the diffusion coefficient results, the percentage of water molecules at each temperature corresponded to the known experimental trend. Silica, as the water absorbent in the hybrid polymer membrane, did not have a strong interaction with water molecules or H3O+ ions; thus the proton conductivities will not be highly affected by adding Krytox-Silica to the Nafion.

Due to its high hydrogen content and its favourable overall thermodynamics magnesium tetrahydroborate has been considered interesting for hydrogen storage applications. In this work we show that unsolvated amorphous magnesium tetrahydroborate can be obtained by reactive ball milling of commercial MgB2 under 100bar hydrogen atmosphere. The material was characterized by solid-state NMR which showed the characteristic features of Mg(BH4)2, together with those of higher borohydride species. High pressure DSC and TPD-MS showed thermal behaviour similar to that of Mg(BH4)2 but with broadened signals. In situ synchrotron X-ray powder diffraction confirmed the amorphous state of the material and showed the typical crystalline decomposition products of Mg(BH4)2 at elevated temperatures.

Two types of membranes, the sulfonated PEEK-WC (poly(oxa-p-phenylene-3,3-phthalido-p-phenylene-oxyphenylene)(SPWC) and Krytox-Si-Nafion® (KSiN) composite membranes are proposed for DMFC applications.The properties based on water uptake, ion exchange capacity, proton conductivity, gas permeability, thermal stabilityand methanol crossover are summarized. The comparative studies on SPWC and Nafion® 117 membranes clarify us that the amorphous sulfonated PEEK-WC polymer shows thermal and mechanical stability with less methanol flux and gas permeability. The membrane also exhibits the increase in water uptake, ion exchange capacity and proton conductivity as sulfuric acid doping agent concentration was increased. The KSiN is unique in term of its miscible hybrid structure of silica particles modified with Nafion® structured Krytox 157 FSL chain (KSi) andNafion®. Based on the KSiN membranes with different KSi content, it was found that when KSi content increased, the reduction of gas permeability, methanol crossover and thermal stability are improved. The composite membrane performs the proton conductivity in the wide range of high temperature (60–130°C).

A nanocomposite membrane of sulfonated montmorillonite/sulfonated poly(ether ether ketone) (SMMT/SPEEK) is proposed for direct methanol fuel cells (DMFCs). The SMMT is clay modified with silane of which the structure consists of a sulfonic acid group for proton conductivity improvement. The micro- and nano-scaled morphologies of the membranes perform the increase in inorganic aggregation with SMMT loading content as confirmed by SEM and AFM. The membrane stability, i.e., the liquid uptake in water and in methanol aqueous solution, as well as the mechanical stability increases with the SMMT loading content whereas thermal stability does not improve significantly. The methanol permeability reduction is obtained when the SMMT loading content increases for various methanol concentrations (1.5–4.5 M). A comparative study of the SPEEK nanocomposite membranes with SMMT and with pristine MMT shows fourfold proton conductivity enhancement after sulfonation. The DMFC single cell tests inform us that all nanocomposite membranes give the significant performance revealed by the plot of current density–voltage and power density.

Nafion (R) and Montmorillonite (MMT) functionalized with Krytox nanocomposite membrane (Krytox-MMT-Nafion (R)) is proposed for DMFC applications. The nanocomposite is obtained with good compatibility between MMT and Nafion (R) via the function of Nafion (R)-like polymer chain namely Krytox 157 FSL. The MMT layers are exfoliated with Nafion (R) polymer matrices and show homogeneity as confirmed by XRD and SEM. The AFM micrographs clarifies the Successful MMT clay dispersion all over the nanocomposite membrane. The thermogravimetric analysis exhibits the improvement in water retention and thermal resistance as compared to Nafion (R) membrane. The membranes perforin for more than 50% reduction in the permcation of methanol in 10%(v/v) Solution at either room temperature or as high as 60 degrees C. The Arrhenius plot suggests the lower activation energy for proton migration in the Krytox-MMT-Nafion (R) membranes than in the Nafion (R) membrane under Grotthus rnechanism. (c) 2007 Elsevier B.V. All rights reserved.

A homogeneous Krytox-Si–Nafion® hybrid membrane is proposed. The hybrid material is successfully prepared using Krytox 157 FSL whose structure is similar to that of Nafion®. Krytox 157 FSL is coupled onto a silica surface via a silane coupling agent to obtain the Krytox-Si. Krytox-Si–Nafion® hybrid membranes show improvement in water retention and an increase in degradation temperature as identified by thermogravimetry analysis. Scanning electron micrographs reveal good dispersion of silica through the membrane. The fully hydrated Krytox-Si–Nafion® hybrid membranes maintain their proton conductivity in a wide range of high temperatures (80–130°C) in ambient condition of a closed system (without additional moisture feeding) as clarified by the plot of conductivity versus temperature.