Hydrogen-treated WO3 nanoflakes show enhanced photostability

Abstract

Here we report that photostability and photoactivity of WO₃ for water oxidation can be simultaneously enhanced by controlled introduction of oxygen vacancies into WO₃ in hydrogen atmosphere at elevated temperatures. In comparison to pristine WO₃, the hydrogen-treated WO₃ nanoflakes show an order of magnitude enhanced photocurrent, and more importantly, exhibit extraordinary stability for water oxidation without loss of photoactivity for at least seven hours. The enhanced photostability is attributed to the formation of substoichiometric WO_3−x after hydrogen treatment, which is highly resistive to the re-oxidation and peroxo-species induced dissolution. This work constitutes the first example where WO₃ can be stabilized for water oxidation in neutral medium without the need for oxygen evolution catalysts. The demonstration of electrochemically stable WO₃ could open up new opportunities for WO₃ based photoelectrochemical and photocatalytic applications.