Efficient and controllable flame method to generate rich oxygen vacancies in WO3 nanosheet arrays to enhance solar water oxidation

A WO3 photoanode is a promising candidate for photoelectrochemical (PEC) water splitting due to its earth-abundance, highly tunable composition, excellent stability, and electrical conductivity. However, its actual PEC performances are inferior to theoretical values, which are challenged by rapid recombination of photogenerated carriers and sluggish water oxidation kinetics. Here, a flame method that has the advantages of being simplistic, controllable, and ultra-efficient is reported to generate a rich oxygen vacancy (OV) in WO3 nanosheet arrays to enhance the PEC performance. The morphology, crystallinity, and PEC performance of the WO3 nanosheet arrays were significantly sensitive to the process parameters. By optimizing the process, rich surface OVs were introduced in the WO3 photoanode within 30 s, while the overall morphology, crystallinity, and conductive substrate were well preserved. The optimum deficient WO3 photoanode exhibited a photocurrent density of 2.40 mA cm−2, which is 3.33 times as high as that of the untreated counterpart. The OVs significantly improved the PEC performance of the WO3 photoanode by enhanced carrier transports and stronger activation for OH− ions. Moreover, the proposed flame method exhibits great versatility in prevalent metal oxides for introducing OVs.