Morphological Modification Of Bi₂O₂CO₃ And Its Photocatalytic Performance Of Composite Materials

Bi₂O₂CO₃ photocatalysts have attracted research interest due to its special layered structure and low toxicity.However,Bi₂O₂CO₃ has a wide band gap and can only be excited by UV light irradiation,which inhibits its practical application.Therefore,a lot of research work has been carried out to improve the photocatalytic activity of Bi₂O₂CO₃,among which morphology modification and heterostructure construction are important methods.In this work,two materials with excellent photocatalytic properties were designed and synthesized by modifying Bi₂O₂CO₃.They were structurally characterized by X-ray powder diffraction,scanning electron microscopy,transmission electron microscopy and X-ray photoelectron spectroscopy.The photocatalytic properties of the materials were investigated by a series of adsorption-degradation experiments in terms of p H,adsorption isotherm,adsorption kinetics,durability and different ion selectivity;finally,the action principles were investigated by mass spectrometry analysis tests on the adsorbed and degraded mock dyes.（1）Bi₂O₂CO₃ without morphological modification（Bi C-W）and Bi₂O₂CO₃ with morphological modification（Bi C-G）were prepared by hydrothermal synthesis using bismuth subsalicylate and ammonia as raw materials and water and ethylene glycol as solvents,respectively.The effects of the morphological modification on the structure and photoelectrochemical properties of Bi₂O₂CO₃ were investigated,and the photocatalytic properties of the two materials were tested by photocatalytic experiments with bisphenol A solution（BPA）and tetracycline hydrochloride（TC）.The optimal synthesis time as well as the optimal molar mass and solvent dosage of bismuth subsalicylate for the degradation of BPA solution in visible light were investigated.Under visible light irradiation,the degradation efficiency of Bi C-G for BPA could reach3.12 times that of the unmodified sample within 2 hours.The increase of specific surface area and the generation of oxygen vacancies added more active sites for it,while a new functional group-COOH was generated,which promoted the photocatalytic activity of the samples.（2）To improve the degradation efficiency of Bi C-G,Bi OI-Bi₂O₂CO₃heterojunction（BOI/Bi C-GX）was further prepared successfully at room temperature using Bi C-G as the precursor.The effects of heterostructure construction on the structure and photoelectrochemical properties of Bi₂O₂CO₃ were investigated;and the optimal molar ratio for photocatalytic degradation under visible light was explored using BPA and TC as organic pollutants.Compared with Bi C-W/G,the photocatalytic efficiency of BOI/Bi C-GX series samples for BPA was improved by 2-3 times,among which the best prime junction BOI/Bi C-G0.5 could reach more than 90%in only 40minutes;the photocatalytic efficiency for tetracycline hydrochloride solution could also all reach more than 95%,among which the catalytic efficiency of BOI/Bi C-G0.5 was higher than that of the unmodified sample respectively.BOI/Bi C-G0.5 catalytic efficiencies were 1.69 and 1.17 times higher than those of unmodified BOI and Bi C-G samples,respectively.The constructed heterojunctions changed the energy gap of the samples and increased their spectral response range,while the polarization charge transfer from Bi OI to Bi₂O₂CO₃ promoted the generation of vacancies on the surface of Bi OI and improved the adsorption and optical properties,thus promoting their photocatalytic performance.