Bulk embedding of Ti-defected TiO2 nano-heterointerfaces in hematite photoanode for boosted photoelectrochemical water splitting

Abstract

The practical application of the most promising α-Fe2O3 photoanode in solar hydrogen generation is facing an awkward challenge arising from its poor bulk carrier transport. Present work demonstrates the acceleration of the carrier transport via embedding the p-type Ti-defected TiO2 (TiO2-VTi) nanocrystals in the n-type Fe2O3 photoanode matrix, which results in significantly improved photoelectrochemical performance. By embedding sub-5 nm TiO2-VTi nanocrystals in the bulk of α-Fe2O3 photoanode, numerous p-n nano-heterointerfaces were constructed for the first time in Fe2O3 photoanode matrix. The formed p-n nano-heterointerfaces lead to 10 times enhancement of charge transfer rate constant (ktran), and 1.5 times reduction of the charge recombination rate constant (krec), which is due to the formation of the built-in electric fields and effective carrier transport and separation at the p-n nano-heterointerfaces of TiO2-VTi/Fe2O3. Such strategy leads to the Fe2O3 photoanode with a reduction of photogenerated carrier transport time by 3 times, resulting in an excellent photocurrent density as high as 1.45 mA cm−2 at 1.23 VRHE, 5 times higher than that of pristine hematite (0.27 mA cm−2). We thus believe that our study opens up a route to regulate hematite or even metal-oxide semiconductor chemical/physical features via p-n nano-heterostructure embedding.