Oxygen vacancy engineering of ultra-small CuWO 4 nanoparticles for boosting photocatalytic organic pollutant degradation.

Nanomaterials have attracted great interest in the field of photocatalytic degradation due to their larger specific surface area and efficient charge/mass transfer ability, which are beneficial for enhancing photocatalytic activity. However, the bandgap of photocatalysts would increase with the size reduction, weakening the photoabsorption ability. Thus the relationship between the size of catalysts and photoactivity should be balanced to achieve optimal photocatalytic performance. Herein, ultra-small CuWO 4 nanoparticles ( ca. 39 nm) with moderate oxygen vacancies (CuWO 4 -OVs) were synthesized by the cascade strategy (ligand confinement@fast calcination). The introduction of oxygen vacancies offset the deficiency of light absorption ability caused by the small size effect. Besides, oxygen vacancies could provide more reaction active sites, conducive to the adsorption and activation of dye molecules and H 2 O. Degradation experiments reveal that the optimized photocatalyst CuWO 4 -OVs 350 shows outstanding photocatalytic activity, and the removal ratio of methylene blue (MB) reaches over 90.26% in 70 min, exceeding that of pure CuWO 4 -air (37.66%). Additionally, the degradation performance of CuWO 4 -OVs 350 surpasses most of the other CuWO 4 -based photocatalytic systems. More importantly, the photocatalytic degradation activity of CuWO 4 -OVs 350 could remain at 88.26% even after five cycles, and high photostability was achieved. This work affords constructive inspiration for synergistic photoactivity enhancement and increase of catalyst reaction active sites to achieve eminent photocatalytic degradation performance.