Ta3N5 nanotubes and -rods: doping, band-gap engineering and stabilization (co-catalysis)

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The present research project tackles solar-based photoelectrolysis of water, using potentially highly active semiconductors in one dimensional (1D) form as the light absorber and energy converter to directly produce hydrogen and oxygen from water. Photoanodes consisting of a 1D nanostructured X:Ta3N5 photoanode (X: modified) will be investigated as a new category of photocatalysts. Due to the relatively suitable small band gap (~2.1 eV) and band edge positions, Ta3N5 will serve as a platform for further modification. Key innovation in this work will be the development of ideally structured and doped Ta3N5 nanotubes/nanorods, modified by bulk doping and surface catalysts to drastically increase their efficiency. The nanostructures used here are based on low cost anodic self-organization processes or on a hydrothermal method, such nanotubes/nanorods have the intrinsic key advantages of a high surface area, directional charge transport, dimensions in the order of charge carrier diffusion length, and the ability to in-situ embed doping species (band-gap engineering). Additionally, in order to alleviate the photocorrosion problem, X:Ta3N5 structures will be decorated with newly developed charge transfer catalysts, such as NiFe layered double hydroxide layers. Recently, our group developed an approach to grow a nanoscale Ta3N5 architecture decorated with suitable catalysts to obtain a 10-fold increase in water splitting efficiency as well as first results on W doped Ta3N5 (shifting the band gap down to 1.75 eV). These preliminary findings will, within the proposed project, be systematically followed up - by studying the properties of the material as a function of growth-morphology, doping, and optimization of self-arranged nanotubular/nanorod Ta3N5 and its stabilization by novel co-catalysts.