An investigation on a WO3/MoO3−x heterojunction photocatalyst for excellent photocatalytic performance and enhanced molecular oxygen activation ability

Abstract

The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of a catalyst. In this paper, MoO_3−x nanosheets with oxygen vacancies were deposited on WO₃ nanoflowers to form a WOM heterojunction, which improved the photocatalytic performance and molecular oxygen activation ability of the catalyst. This novel WOM heterojunction exhibited excellent photoactivity for degrading rhodamine B (RhB), photocatalytic water splitting ability and molecular oxygen activation ability under sunlight irradiation. Among all the samples, WOM_83% could degrade 98% of 30 ppm RhB in 40 min. Meanwhile, WOM_83% exhibited the highest hydrogen generation rate (4214.2 μmol h⁻¹ g⁻¹) and the strongest TMB oxidation capacity, and can generate 2.23 μmol of ·O₂⁻ in 50 min. The enhanced photocatalytic performance via heterojunction construction may be attributed to these following reasons: (i) higher light absorption achieved by the MoO_3−x and WO₃ composite; (ii) the matched energy band gap of MoO_3−x and WO₃ led to higher photogenerated carrier mobility; (iii) MoO_3−x with oxygen vacancies as electron traps suppressed the photogenerated carrier recombination; (iv) enhanced molecular oxygen activation ability of the WOM heterojunction, such as the production of ·O₂⁻. The measurements for TMB photo-oxidation and ·O₂⁻ showed excellent molecular oxygen activation ability of WOM heterojunctions. Finally, a possible photocatalytic mechanism was proposed. This study provided a viable option for the application of materials with oxygen vacancies to remove pollutants and improve molecular oxygen activation ability.