Photoelectrochemical water splitting promoted with a disordered surface layer created by electrochemical reduction.

The recent discovery of colored TiO2 indicated that the disordered surface layer over the TiO2 particles/photoelectrodes is beneficial for higher photocatalytic performance; however, the role of the disordered surface TiO2 layer is not well understood. Here, we report an electrochemical strategy for tuning the surface structure of TiO2 nanorod arrays (NRAs) and try to understand the role of the disordered surface TiO2 layer. Photoelectrodes of TiO2 NRAs with a disordered shell were prepared by an electrochemical reduction method. The photocurrent of the NRAs with a disordered shell can reach as high as ∼1.18 mA/cm(2) at 1.23 V, which is 2.2 times of that of the pristine TiO2 NRAs. Our results show that the surface disordered layer not only improves the bulk charge separation but also suppresses the charge recombination at the electrode/electrolyte interface, acting as an efficient water oxidation cocatalyst of photoelectrochemical cell for solar water splitting.