Vapor Deposition of Semiconducting P Allotropes into TiO2 Nanotube Arrays for Photo-Electrocatalytic Water Splitting

  • Author(s) / Creator(s)
  • Recent evidence of exponential environmental degradation will demand a drastic shift in research and development towards exploiting alternative energy resources such as solar energy. Here, we report the successful low-cost and easily accessible synthesis of hybrid semiconductor@TiO2 nanotube photocatalysts. In order to realize its maximum potential in harvesting photons in the visible light range, TiO2 nanotubes have been loaded with earth abundant, low band gap fibrous red P and black P. SEM-, STEM-EDS, XRD, Raman spectroscopy, XPS and UV-Vis measurements have been performed, substantiating the deposition of fibrous red and black P on top and inside the cavities of 100 μm long electrochemically fabricated nanotubes. The nanotubular morphology of titania and a vapor transport technique is utilized to form heterojunctions of P and TiO2. Compared to pristine anatase 3.2 eV-TiO2 nanotubes, the creation of heterojunctions in the hybrid material resulted in 1.5 – 2.1 eV photoelectrocatalysts. An enhanced photoelectrochemical water splitting performance under visible light compared with the individual components resulted for the phosphorus@TiO2 hybrids. This feature is due to synergistically improved charge separation in the heterojunction and more effective visible light absorption. The electronic band structure and charge carrier dynamics are investigated in detail by using UPS and KPFM, to elucidate the charge separation mechanism. A Fermi level alignment in phosphorus@TiO2 heterojunctions leads to a more reductive flat band potential and a deeper valence band compared to pristine phosphorus, and thus facilitate better water splitting performance. Our results demonstrate effective conversion efficiencies for the nanostructured hybrids that may enable future applications in optoelectronic applications such as photodetectors, photovoltaics, photoelectrochemical catalysts and sensors.

  • Date created
  • Subjects / Keywords
  • Type of Item
    Article (Published)
  • DOI
  • License
    Attribution-NonCommercial 4.0 International