Surface polarization enables high charge separation in TiO2 nanorod photoanode

Poor charge separation efficiency of semiconductors often stands in the way of photoelectrochemical (PEC) water splitting realization. In this report, a surface polarized TiO2 photoanode is obtained via −OH moiety decoration, which achieves a fundamentally improved charge separation efficiency of about 94% at 1.23 VRHE. Detailed data shows that these hydroxyls with electric dipoles polarize the surface, inducing substantial electric field in the surface region, and elevating band edges so as to form a homojunction within TiO2. Such serves as the direct driving force for the photogenerated charge separation and migration. Moreover, these hydroxyls also facilitate water oxidation kinetics. Without typical doping or cocatalyst, surface polarized TiO2 photoanode delivers a considerably increased photocurrent density of about 1.41 mA·cm−2 at 1.23 VRHE (AM 1.5 G) and a cathodic shift on onset potential over 200 mV. This report highlights new opportunities to modulate charge separation by surface polarization for the construction of robust photoanodes.