Tannic Acid-Fe complex with dual-function modified TiO2 photoanode for enhanced photoelectrochemical water oxidation

TiO2, as a promising photoanode material, has been commonly investigated in recent years, but its poor photoelectric conversion efficiency limits its practical application. Here, we fabricated in-situ a low-cost and eco-friendly tannic acid-Fe modified TiO2 nanorod arrays photoanode (TiO2/Tan-Fe) with improved photoelectric conversion efficiency. Compared with pristine TiO2 nanorod arrays (0.55 mA/cm2 at 1.23 V vs. RHE), the TiO2/Tan-Fe exhibits the enhanced photocurrent density (0.98 mA/cm2 at 1.23 V vs. RHE). The enhancement of photoelectrochemical (PEC) performance is mainly attributed to tannic acid-Fe as a light absorber with a wide absorbance region and increasing charge separation and transport in the composite photoanode, which is testified via ultraviolet–visible absorption, enhanced charge separation efficiency and Motty-Schottky curves, and so on. Importantly, the modification of tannic acid-Fe as a cocatalyst facilitates the water oxidation dynamic, which is confirmed by charge injection efficiency and oxygen evolution reaction (OER). These results indicate that the rationally designed and assembled photoanode has the potential to improve PEC performance and fabricate solar cell for efficient photoelectric conversion.