Solid-state hydride compounds are a promising option for efficient and safe hydrogen-storage systems. Lithium reactive hydride composite system 2LiBH4 + MgH2/2LiH + MgB2 (Li-RHC) has been widely investigated owing to its high theoretical hydrogen-storage capacity and low calculated reaction enthalpy (11.5 wt % H2 and 45.9 kJ/mol H2). In this paper, a thorough investigation into the effect of the formation of nano-TiAl alloys on the hydrogen-storage properties of Li-RHC is presented. The additive 3TiCl3·AlCl3 is used as the nanoparticle precursor. For the investigated temperatures and hydrogen pressures, the addition of ∼5 wt % 3TiCl3·AlCl3 leads to hydrogenation/dehydrogenation times of only 30 min and a reversible hydrogen-storage capacity of 9.5 wt %. The material containing 3TiCl3·AlCl3 possesses superior hydrogen-storage properties in terms of rates and a stable hydrogen capacity during several hydrogenation/dehydrogenation cycles. These enhancements are attributed to an in situ nanostructure and a hexagonal AlTi3 phase observed by high-resolution transmission electron microscopy. This phase acts in a 2-fold manner, first promoting the nucleation of MgB2 upon dehydrogenation and second suppressing the formation of Li2B12H12 upon hydrogenation/dehydrogenation cycling.

In this work, we study the electronic and atomic structural modifications occurring in TiO 2 anatase nanoparticles as anode materials in Naion batteries upon sodiation and desodiation. The structural investigation is performed over both long-and short-range order by combining a comprehensive extended X-ray absorption fine structure (EXAFS) characterization with X-ray diffraction (XRD). The evolution of the electronic structure upon cycling is qualitatively investigated by X-ray absorption near-edge structure (XANES) analysis. The goal of this work is to correlate the outstanding electrochemical performance of carbon-coated TiO 2 anatase nanoparticles in sodium batteries with the electronic and structural modifications induced during the sodiation and desodiation processes upon cycling. This work also demonstrates for the first time a coherent explanation of the structural changes observed, where an electrochemically induced short-range ordering is revealed upon cycling.

Polymer electrolyte fuel cells (PEFCs) offer an efficient way of chemical-to-electrical energy conversion that could drastically reduce the environmental footprint of the mobility and stationary energy supply sectors, respectively. However, PEFCs can suffer from severe degradation during start/stop events, when the cathode catalyst is transiently exposed to very high potentials. In an attempt to mitigate corrosion of conventional carbon support materials for Pt catalyst nanoparticles under these conditions, conductive metal oxides like antimony-doped tin oxide (ATO) are considered alternative support materials with improved corrosion resistance. A combined in situ anomalous small-angle X-ray scattering and post mortem transmission electron microscopy study reveals PEFC-relevant degradation properties of ATO-supported Pt in comparison to carbon-supported Pt catalysts. Against expectation, the superior stability of ATO-supported Pt nanoparticles cannot be merely explained by improved support corrosion resistance. Instead, the dominant loss mechanism of electrochemical Ostwald ripening is strongly suppressed on ATO support, which can be explained with a potential-dependent switching of support oxide surface conductivity. This electrochemical transistor effect represents an important design principle for the development of optimized metal oxide support materials that protect supported Pt nanoparticles at high potentials, where careful consideration of the metal oxide flat-band potential is required in order to maintain high catalyst performance at normal PEFC cathode operation conditions at the same time.

The nanostructure of hydrogenated amorphous silicon (a-Si:H) is studied by a combination of small-angle X-ray (SAXS) and neutron scattering (SANS) with a spatial resolution of 0.8 nm. The a-Si:H materials were deposited using a range of widely varied conditions and are representative for this class of materials. We identify two different phases which are embedded in the a-Si:H matrix and quantified both according to their scattering cross-sections. First, 1.2 nm sized voids (multivacancies with more than 10 missing atoms) which form a superlattice with 1.6 nm void-to-void distance are detected. The voids are found in concentrations as high as 6 10 19 cm -3 in a-Si:H material that is deposited at a high rate. Second, dense ordered domains (DOD) that are depleted of hydrogen with 1 nm average diameter are found. The DOD tend to form 10-15 nm sized aggregates and are largely found in all a-Si:H materials considered here. These quantitative findings make it possible to understand the complex correlation between structure and electronic properties of a-Si:H and directly link them to the light-induced formation of defects. Finally, a structural model is derived, which verifies theoretical predictions about the nanostructure of a-Si:H.