In situ transformation of TiO2 hierarchical nanostructures toward efficient photoelectrochemical water splitting

TiO2 hierarchical nanomaterials have been intensively investigated as a very promising photoanode in photoelectrochemical water splitting due to its combined effects of large surface area and fast electron transfer. However, the TiO2 hierarchical nanostructures prepared by most prevailing synthesis methods currently are at distinct disadvantages such as complicated process, poor controllability, poor interfacial contact, excessive impurities and so on. Here we report a facile route to construct a well-defined TiO2 hierarchical nanostructure via in-situ transformation of TiO2 nanoparticles with highly exposed {001} facets in the tube wall of the pristine TiO2 nanotube arrays. The resulted TiO2 hierarchical nanostructures exhibit enhanced light harvesting, lowe recombination rate of photo-generated charger carrier. Upon these synergistic effects, the target hierarchical nanostructure shows significantly improved PEC performance and excellent photo-switching response with good reproducibility and stability. Corresponding photocurrent density and photon-to-current efficiency achieve 0.76 mA cm−2 and 0.50%, respectively, which show an enhancement of 1.70 and 1.32 times to those of the control one. This work provides a possible route for fabrication of TiO2 starting materials with decent efficiencies.