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Polymer electrolyte membrane (PEM) electrolysis is an ideal method for the direct conversion of regenerative energy into hydrogen. A key component of PEM electrolysis stacks is the porous transport layer (PTL), which is usually comprised of titanium to withstand the harsh conditions of water splitting. This present study investigates the potential of tape casting as a means of mass producing titanium transport layers in a cost-effective way. Gasatomized and hydrogenation-dehydrogenation titanium powders are used as starting materials. A systematic study is conducted to find processing parameters, which can demonstrate the potential of tape casting as a means of manufacturing large-scale porous transport layers for PEM electrolyzers. For proof of concept, the dimensions of the porous transport layer are scaled up to 470 Â 470 mm 2 (at a thickness of 300 μm) and the component is successfully operated in an industrial electrolyzer under realistic conditions.

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The growth, crystal structure, strain relaxation and room temperature transport characteristics of GaAs/InSb core-shell nanowires grown using molecular beam epitaxy are investigated. Due to the large lattice mismatch between GaAs and InSb of 14%, a transition from island-based to layer-like growth occurs during the formation of the shell. High resolution transmission electron microscopy in combination with geometric phase analyses as well as X-ray diffraction with synchrotron radiation are used to investigate the strain relaxation and prove the existence of different dislocations relaxing the strain on zinc blende and wurtzite core-shell nanowire segments. While on the wurtzite phase only Frank partial dislocations are found, the strain on the zinc blende phase is relaxed by dislocations with perfect, Shockley partial and Frank partial dislocations. Even for ultrathin shells of about 2 nm thickness, the strain caused by the high lattice mismatch between GaAs and InSb is relaxed almost completely. Transfer characteristics of the core-shell nanowires show an ambipolar conductance behavior whose strength strongly depends on the dimensions of the nanowires. The interpretation is given based on an electronic band profile which is calculated for completely relaxed core/shell structures. The peculiarities of the band alignment in this situation implies simultaneously occupied electron and hole channels in the InSb shell. The ambipolar behavior is then explained by the change of carrier concentration in both channels by the gate voltage.

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