Endotaxial Growth of [100]-Oriented TaON Films on LiTaO3 Single Crystals for Enhanced Photoelectrochemical Water Splitting

To enhance the photoelectrochemical (PEC) water splitting performance of TaON photoanodes, we grow [100]-oriented TaON films by nitridating the (012) surface of single crystal LiTaO3 under NH3/CCl4 mixed gas. The endotaxial growth of [100]-oriented TaON from the (012) surface of LiTaO3 produces TaON nanoporous films that can be completely exfoliated from the LiTaO3 substrate. The exfoliated film consists of interconnected worm-like TaON nanoparticles aligned along the [100] direction perpendicular to the film surface across the film thickness. This oriented TaON porous nanostructure facilitates the transfer of photogenerated electrons across the film, hence enhancing the separation of photogenerated electron-hole pairs on the film surface. As a result, the TaON photoanode fabricated by the annealed oriented TaON films exhibits excellent PEC performances with a photocurrent of 5.32 mA cm(-2) at 1.23V versus RHE under AM 1.5G simulated solar irradiation. This value is one of the highest photocurrents among the TaON photoanodes reported so far. Our work provides a new method to fabricate highly oriented crystalline films through an endotaxial growth process from single crystalline substrates. This method can be used to fabricate highly efficient photoelectrodes for PEC water splitting, and is expected to be useful in many other fields.