Hierarchical TiO2 Photoanodes with Spatial Charge Separation for Efficient Oxygen Evolution Reaction

Charge separation and transfer are crucial to determine photoelectrochemical (PEC) water splitting performance. Herein, a hierarchical bottom‐up approach for fabricating TiO 2 nanorod arrays with an Au nanolayer and Sn 3 O 4 cocatalysts is demonstrated. The hierarchical Sn 3 O 4 /TiO 2 /Au photoanode exhibits a significantly enhanced photocurrent density of 2.5 mA cm −2 at 1.23 V RHE under AM 1.5G irradiation, which is about 5 times higher than that of pristine TiO 2 (0.5 mA cm −2 at 1.23 V RHE ). The significantly enhanced PEC properties are attributed to the spatial charge separation among Au nanolayer and Sn 3 O 4 cocatalysts. More specifically, the bottom Au nanolayer can accelerate the electron transfer from TiO 2 to fluorine doped tin dioxide (FTO) substrate, and the surface Sn 3 O 4 nanoflakes can effectively capture holes and provide abundant active sites for oxygen‐evolution reaction. These demonstrations may offer a new insight for rational design and construction of highly efficient TiO 2 ‐based PEC devices for solar water splitting.