s Promoted Photoelectrocatalytic Hydrogen Production Performance of TiO2 Nanowire Arrays by Al2O3 Surface Passivation Layer

Background: TiO2 is one of the most promising photocatalysts in photoelectrocatalytic (PEC) water splitting due to its high chemical stability, photocorrosion resistance, nontoxicity and low cost. One dimensional TiO2 nanowire arrays are expected to provide a large surface area and a direct electrical pathway for rapid photogenerated electron transport. However, the photocatalytic performances of TiO2 nanowire arrays are largely limited by the surface charge recombination because of the large amount of surface defects. Methods: In this work, novel TiO2/Al2O3 core-shell nanowire arrays with conformal Al2O3 surface passivation layer were investigated for PEC water splitting. Rutile TiO2 nanowire arrays were successfully grown on carbon cloth by hydrothermal method, and atomic layer deposition (ALD) was used to deposit uniform Al2O3 layer on TiO2 nanowires. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, photoelectrochemical measurements, PEC water splitting performance of TiO2/Al2O3 core-shell nanowire arrays were systematically investigated in this work. Results: Compared with that of pure TiO2 nanowire arrays, the photocurrent response of the TiO2/Al2O3 core-shell nanowire arrays is enhanced about 1.7 times under simulated solar light irradiation. And the PEC hydrogen production (bias potential=0.2 V) under simulated solar light irradiation presents 5.6 times enhancement on the TiO2 nanowire arrays after Al2O3 passivation coating. Conclusion: The improved performance of PEC hydrogen production of TiO2 is attributed to the reduction of surface recombination caused by the chemical passivation and field-effect passivation effect of Al2O3 passivation layer. The results provide a potential way to develop efficient photoelectrodes in PEC water splitting system.