Morphology and interfacial energetics controls for hierarchical anatase/rutile TiO2 nanostructured array for efficient photoelectrochemical water splitting.

In this work, a three-dimensional (3D) hierarchical TiO2 nanostructured array is constructed on the basis of the considerations of morphology and interfacial energetics for photoelectrochemical water splitting. The photoelectrode is composed of a core-shell structure where the core portion is a rutile TiO2 nanodendrite (ND) array and the shell portion is rutile and anatase TiO2 nanoparticles (NPs) sequentially located on the surface. The TiO2 ND array provides a fast electron transport pathway due to its quasi-single-crystalline structure. The 3D configuration with NPs in the shell portion provides a larger surface area for more efficient photocharge separation without significantly sacrificing the electron collection efficiency. Moreover, anatase TiO2 NPs constructed on the surface of the ND/rutile TiO2 NP nanostructured array enhance charge separation and suppress charge recombination at the interfacial region due to the higher conduction band edge of anatase TiO2 compared to that of rutile TiO2. A photocurrent density and photoconversion efficiency of 2.08 mA cm(-2) at 1.23 V vs reversible hydrogen electrode (RHE) and 1.13% at 0.51 V vs RHE are, respectively, attained using the hierarchical TiO2 nanostructured array photoelectrochemical cell under illumination of AM 1.5G (100 mW cm(-2)).