Electrochemical In-situ Synthesis And The Doping Modification Of BiF₃ Thin Films

Solar photocatalytic advanced oxidation technology is one of the effective methods to deal with persistent toxic organic pollutants in the environment,and the development of new high-efficiency photocatalytic materials is a key scientific problem in the advance of photocatalytic technology.Recently,the novel Bi-based semiconductor photocatalytic materials have unique layered structures and electronic properties,giving them good photocatalytic activity and stability.Among them,BiF₃,with the more positive valence band,exhibits excellent strong oxidizing ability in the photocatalytic reaction process.Besides,the advantages of its cheap raw materials,stable structure,and non-toxic harmlessness have been attracted great attentions.In order to solve the solid-liquid separation and recycle problems of powder catalysts,photocatalyst immobilization has always been cansidered as an ideal application way for scientists.In this paper,photocatalytic Bi F₃ thin film was directly synthesized from Bi-plate using economical and environmental-friendly and simple in-situ electrochemical method.With the help of the surface plasmon resonance effect and enhanced light absorption ability for noble metals,Pd was deposited on BiF₃ thin films by photoreduction method,achieving the enhanced light absorption degree,photocatalytic activity and stability.Our findings shoulf provide the experimental methods and theoretical basis for in-depth development of BiF₃ thin films.The main research contents are as follows:?1?In this study,the Bi metal plate was used as the anode,graphite as the cathode,and NH₄F was dissolved in a mixed solution of ethylene glycol and water with the volume ratio of 19:1,where,BiF₃ thin films were successfully prepared by simple in-situ electrochemical method at room temperature.The X-ray diffraction?XRD?,Scanning electron microscopy?SEM?,Transmission electron microscopy?TEM?,UV-Vis DRS and Density functional theory?DFT?were employed to characterize the crystallinities,structures,morphologies,optical properties and energy band structures of as-prepared BiF₃ thin films.The photocatalytic activity and stability of BiF₃ thin films were evaluated by the degradation of Rhodamine B?RhB?under simulated sunlight irradiation.The results show that the BiF₃ thin films exhibit the nanosheet structure with high purity,excellent photocatalytic activity and stability.The conduction band minimum and the valence band maximum of Bi F₃ thin films are mainly contributed by Bi 6p and F 2p orbital electrons,respectively.It is found that,with the increase of electrolyte concentration,the structural morphologies of BiF₃ thin films changed,resulting in that the photocatalytic activity of BiF₃ thin films first enhanced and then decreased.When the electrolyte concentration is1.5%,the photocatalytic degradation efficiency of Rhodamine B?RhB?reaches99.2%under 5 h simulated solar light irradiation,and still remains above 81%after being used four times.Furthermore,we propose the possible formation mechanism of Bi F₃ thin films on Bi plate via novel in-situ electrochemical method.?2?The Pd/BiF₃ thin films were prepared by a simple photoreduction method at room temperature.The XRD,SEM,UV-Vis DRS and XPS were employed to characterize the crystallinities,structures,morphologies,optical properties and elemental compositions of as-prepared Pd/Bi F₃ thin films.The effect of different Pd loading amounts on the photocatalytic performance of BiF₃ thin films was investigated using RhB as the target degradant under simulated sunlight irradiation.The results show that the Pd/Bi F₃ thin films exhibit good crystallinity and the nanosheet structure.Loading noble metal Pd on the surface of BiF₃ thin films narrows the bandgap from the original 3.70 eV to 3.03 eV,and extends into the visible light absorption range.The noble metal Pd can be loaded uniformly on the surface of BiF₃ thin films.The Pd loading amounts have certain influence on the structure,photoatalytic activity and stability of BiF₃ thin films.When Pd loading amount is 2.0%,the photocatalytic degradation efficiency of RhB reaches 98.9%under 2 h simulated solar light irradiation,and still remains above 76%after being used four times.Furthermore,the capture experiments reveal that the main active species of2.0%-Pd/Bi F₃ thin film are hydroxyl radical?·OH?and superoxide radical?·O₂^-?.