An investigation on a WO₃/MoO_3-x heterojunction photocatalyst for excellent photocatalytic performance and enhanced molecular oxygen activation ability

The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of a catalyst. In this paper, MoO3-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, WOM83% could degrade 98% of 30 ppm RhB in 40 min. Meanwhile, WOM83% exhibited the highest hydrogen generation rate (4214.2 mu mol h(-1) g(-1)) and the strongest TMB oxidation capacity, and can generate 2.23 mu mol of O-2(-) in 50 min. The enhanced photocatalytic performance via heterojunction construction may be attributed to these following reasons: (i) higher light absorption achieved by the MoO3-x and WO3 composite; (ii) the matched energy band gap of MoO3-x and WO3 led to higher photogenerated carrier mobility; (iii) MoO3-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 O-2(-). The measurements for TMB photo-oxidation and O-2(-) 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.