CuO-CuX NPs rich in oxygen vacancies modulated by halogen ions and their application in photocatalytic degradation.

Oxygen vacancies (OVs) are one of the most important strategies to modulate the photocatalytic properties of nanomaterials, but usually the preparation of OVs is complicated and difficult, so the development of a simple, gentle, and efficient method to prepare OVs is crucial. Herein, Cu/CuO NPs with a small number of OVs were prepared initially by a one-step reduction method. Then, with the addition of halogen ions (F, Cl, Br, and I), CuO-CuX NPs enriched with OVs were obtained at room temperature. Furthermore, the effects of the addition of the halogen ions were analyzed. CuO-CuF NPs had the highest content of OVs, which enabled efficient photocatalytic degradation of methylene blue (MB). Compared with Cu/CuO NPs, CuO-CuX NPs exhibit higher content of OVs, narrower band gaps, and significantly improved photocurrent signal. These findings suggest that the introduction of halogen ions promotes the efficiency of light collection and charge carrier separation and thus improves the degradation of MB. This work may open up new avenues for the design of superior photocatalysts for dealing with organic contaminants through engineering of OVs.