Controllable Synthesis Of Layered Bismuth Oxyhalides And Their Degradation Behavior For Typical PPCPs

Pharmaceuticals and personal care products(PPCPs)have gradually attracted wide attention as a new type of micropollutants.In recent years,PPCPs have been continuously detected in surface water,groundwater,and even drinking water.The accumulation of PPCPs and their metabolites can cause biological toxicity and endocrine disruption,posing a potential threat to human health.Heterogeneous photocatalysis is a green advanced oxidation technique and is considered as one of the most promising methods for effectively removing PPCPs in water.This paper aims to explore the controllable construction of BiOX(X=Cl,Br)with a unique layered structure and its application in the removal of typical PPCPs in water.The controllable synthesis of three-dimensional hollow structure BiOX was achieved by a simple ionic liquid microemulsion method,and the relationship between photocatalytic properties and its morphology,crystal structure,energy band position and surface structure was systematically investigated.Ultrathin BiOCl half-shells have been synthesized via an ionic liquid-in-water(IL/W)microemulsion,applying the liquid-liquid boundary of the emulsion system as a template.Surfactant TX-100 acted as the stabilizer of the IL-microemulsion,which is of critical importance for the formation of BiOCl half-shells.The hollow structures were characterized using X-ray diffraction,scanning and transmission electron microscopy,diffuse reflectance spectroscopy and specific surface area,respectively.Possible formation mechanisms for the BiOCl half-shells were discussed.Moreover,the ultrathin BiOCl half-shells exhibited distinctly enhanced photocatalytic efficiency toward the degradation of representative antibiotic agent ciprofloxacin(CIP)and tetracycline hydrochloride(TC)under solar light irradiation as compared to BiOCl nanosheets.The photogenerated reactive species are verified by scavenger experiments,which reveals that·O2-and h+were the two major photoactive species toward the photodegradation of CIP over ultrathin BiOCl half-shells under solar-light.The enhanced activities of ultrathin BiOCl half-shells were mainly ascribed to the synergistic effect of the increased light-harvesting,larger BET surface area,faster separation and transfer of electron-hole pairs.The novel Bi-rich Bi4O5Br2 with tunable morphologies of two-dimentional(2D)nanosheets(NSs),three-dimentional(3D)monodisperse layered microspheres(LMs)and hollow spheres(HSs)has been successfully synthesized via an ionic liquid-in-water(IL/W)microemulsion method.Surfactant TX-100 served as the stabilizer of the IL/W microemulsion,and its concentration significantly influenced the morphology and size of the resulting Bi4O5Br2 crystal.Possible formation mechanisms have also been discussed.UV-visible diffuse-reflectance spectra and Density function theory(DFT)calculations indicated that Bi4O5Br2 possessed stronger visible light adsorption and more negative conduction band minimum(CBM),which is beneficial to effectively activate molecular oxygen to produce·O2-.The photocatalytic activity of Bi-rich Bi4O5Br2 with varied shapes was investigated and compared with BiOBr for the removal of fungicide o-phenylphenol(OPP)and antibacterial agent norfloxacin(NOR)and tetracycline hydrochloride(TC)under visible light irradiation.The as-prepared Bi4O5Br2 HSs and LMs possess higher photocatalytic efficiency than Bi4O5Br2 and BiOBr NSs,which is attributed to the hollow/layered spherical structures and Bi-rich strategies.The·O2-and h+are identified to be the major photoactive species during the photo-degradation process by scavenger experiments and EPR methods.This study is expected to provide a stepping stone to purposively design and explore other novel hollow structures with controllable morphology and enhanced photocatalytic activity.Bi3O4Br hierarchical hollow spheres composed of {001}-facet exposed nanosheets have been successfully synthesized via ionic liquid microemulsion approach.By adjusting the concentration of TX-100,the size of the layered hollow spheres and the thickness of the nanosheets can be easily regulated.Through the SEM and XRD analysis of hollow spheres obtained with different hydrothermal times,the possible formation mechanism of the {001}-facet exposed Bi3O4Br hierarchical hollow spheres was discussed.For the visible light degradation of a variety of phenol derivatives(APAP,PTBP,ONP and MPB),Bi3O4Br-001-HSS showed excellent non-selective photooxidation ability.The main reasons for the enhanced photocatalytic activity are as follows:first,the Bi-rich strategy has the suitable energy band position;secondly,the hollow structure can improve the light-capturing capability,generate more photoelectron-hole pairs,and the larger specific surface area has more active sites;most importantly,the strength of the internal electrostatic field is positively correlated with the exposure rate of the {001} facet,while the reduction of the sheet thickness gives it more {001} facet,further strengthening the internal electric field,improve photogenerated carrier separation and migration efficiency.