Oxygen vacancy engineering of ultra-small CuWO₄ 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 CuWO₄ nanoparticles (ca. 39 nm) with moderate oxygen vacancies (CuWO₄-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 H₂O. Degradation experiments reveal that the optimized photocatalyst CuWO₄-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 CuWO₄-air (37.66%). Additionally, the degradation performance of CuWO₄-OVs 350 surpasses most of the other CuWO₄-based photocatalytic systems. More importantly, the photocatalytic degradation activity of CuWO₄-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.