Preparation of well-aligned WO3 nanoflake arrays vertically grown on tungsten substrate as photoanode for photoelectrochemical water splitting

Well-aligned WO3 nanoflake arrays (WNA) as effective photoanode was vertically fabricated on tungsten sheet through a facile hydrothermal process. Before reaction, the tungsten sheet was pre-annealed to produce a thin-layer WO3 on surface to serve as seeded sites for crystal growth in hydrothermal reaction, which also provided a strong connection between the growing WO3 and substrate. Polyethylene glycol (PEG) was used as the structure-directing agent to confine the crystal growth. This preparation route obviously facilitated the charge transfer and reduced the recombination of photoexcited electron/hole. The saturated photocurrent density and IPCE value were found to be 2.35 mA cm− 2 at 1.5 V and 56% which were much higher than that prepared in the absence of pre-annealed WO3 layer and PEG.

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► We present a typical hydrothermal process to synthesize effective WO3 photoanode.
► Pre-annealed tungsten sheet was used as seeded substrate for nanocrystal growth.
► PEG was employed as structure directing agent to confine the nanocrystal growth.
► As-prepared product of WNA retained the mechanical flexibility and stability.
► The WNA showed superior photoelectrochemical properties for water splitting.