Mechanistic insight into the influence of transition metal oxide loading on BiVO4 for effective peroxymonosulfate activation toward highly efficient degradation of sulfamethoxazole.

In this paper, a series of monoclinic crystal structure bismuth vanadate (m-BiVO4) photocatalysts with different transition metal oxide loading amounts (MO x @BiVO4, M represents Mn, Fe, Co, Ni and Cu) were constructed to boost photocatalytic sulfamethoxazole (SMX) degradation with peroxymonosulfate (PMS) assistance. MO x @BiVO4 samples exhibited enhanced light absorption properties, specific interfacial charge transfer ability and reactive oxygen species (ROS) production in comparison with pristine BiVO4. The degradation efficiencies of MnO x @BiVO4, FeO x @BiVO4, CoO x @BiVO4, NiO x @BiVO4 and CuO x @BiVO4 for SMX were 92.74%, 96.34%, 97.80%, 93.31% and 99.89% with PMS activation in 90 min visible light illumination, respectively. The crystalline structure, elementary composition, photocatalytic activity and degradation mechanism of MO x @BiVO4 samples were investigated systematically with the techniques of XRD, Raman spectroscopy, TEM, XPS, UV-vis DRS, PC, EIS, PL and EPR. The results showed that all MO x were successfully loaded on BiVO4. The redox cycling of M acted as a charge transfer intermediate to accelerate interfacial charge separation, while also serving as adsorption and activation sites for PMS, thereby promoting efficient mass transfer in the heterogeneous system. EPR and quenching experiments demonstrated that 1O2, SO4˙-, ˙OH and ˙O2 - species were all generated in the MO x @BiVO4 system; in particular, ˙OH and 1O2 played dominant roles in the degradation of SMX. This study provides inspiration for the design of high-performance MO x -supported photocatalytic activators and broadens their potential applications in environmental remediation.