Enhanced Visible Light Activity in Titania Nanotube Based Heterojunction Photocatalysts for Solar Fuel Generation

The world energy consumption has been steadily increasing with technological advancements and growing population. Bulk of this energy is currently derived from fossil fuels, which are known to be responsible for the greenhouse gas emission and associated environmental problems. Solar fuels such as hydrogen derived from water using semiconductor photocatalysts is a sustainable approach.   Nonetheless, most photocatalysts hold drawbacks such as wide band gap and high recombination rate of photo-generated electrons and holes, limiting the practical applications. In a recent study, it was demonstrated that a visible light active photoelectrode for photoelectrochemical water splitting could be developed by coupling the wide band gap titanium dioxide nanotubes with two dimensional (2D) narrow band gap iron oxide called hematene (Nat. Nanotech., 13, 602-609, 2018). We have extended the studies to a 1D titania/2D FeTiO₃ heterostructure and observed photo-generated carrier transfer from 2D FeTiO₃ to 1D TiO₂ through the heterojunction even though the positions of the conduction bands were not favorable for such a transfer. In this presentation, we will discuss these results and the enhanced visible light driven solar photoelectrochemical hydrogen generation using these photoelectrodes.