Comparative study of BiVO₄ and BiVO₄/Ag₂O regarding their properties and photocatalytic degradation mechanism

BiVO₄, as a visible light catalyst, produces photogenerated electrons and photogenerated holes that are easy to recombine. In this paper, a BiVO₄/Ag₂O composite was prepared to promote the separation of photogenerated carriers of BiVO₄. Compared with BiVO₄, the properties and photocatalytic activity of BiVO₄/Ag₂O were obviously improved. The improvement of BiVO₄/Ag₂O was reflected in the better separation of photogenerated electrons and photogenerated holes, higher UV-visible maximum absorption wavelength, and stronger ability to degrade doxycycline. The effects of Ag₂O on the crystal structure, the morphology and the binding energy of BiVO₄ were analyzed by XRD, XPS and SEM, and the existence of a heterojunction in BiVO₄/Ag₂O was confirmed. The results of capture experiments showed that the photocatalytic processes of BiVO₄ and BiVO₄/Ag₂O produced hydroxyl radicals (˙OH), holes (h⁺) and superoxide radicals (˙O₂⁻). However, the contribution of active species was different in the two systems. The degradation pathways and intermediate products of doxycycline were analyzed by UPLC-QTOF. This work proposed a new method for the preparation of BiVO₄/Ag₂O particles with remarkable photocatalytic activity, and provided a reference for the degradation of doxycycline.