BiO(OH)_xI_1-x solid solution with rich oxygen vacancies: interlayer guest hydroxyl for improved photocatalytic...

A series of BiO(OH)_xI_1-x solid solution (SS) catalysts were successfully prepared by ion exchange of I^- and OH^- between the [Bi₂O₂]²⁺ layers. The morphology and microstructure were studied in depth using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) method, etc. Tunable absorption in the visible-light region was achieved by changing the proportion of OH^- to I^-. Due to the etching effect of OH^-, oxygen vacancies (OVs) greatly increased for the SS catalysts, and were confirmed by X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and electron paramagnetic spectroscopy (EPR). The unique composition of OH^-, I^-, OV, and [Bi₂O₂]²⁺ layers in BiO(OH)_xI_1-x materials resulted in diverse photoexcitations. The BiO(OH)_0.45I_0.55 photocatalyst displayed a 10-fold-improved 2-chlorophenol (2-CP) degradation rate compared to BiOI. The interfacial reaction process by the photoinduced valence-band holes and conduction-band electrons proved to be a more efficient pathway for organic pollutant degradation by the BiO(OH)_xI_1-x SS photocatalyst. The OVs in the SS photocatalyst facilitated photoexcited and electron migration and transformation.