Preparation Of Bismuth Oxide Composite Electrode And Its Photoelectrocatalytic Performance

With the rapid development of textile printing and dyeing industry,metallurgy and chemical industry,a large amount of industrial wastewater is discharged,of which the treatment of biodegradable organic matter has become a pressing problem to be solved.Photocatalytic technology can use sunlight for wastewater treatment without secondary pollution,and is considered an environmentally friendly wastewater treatment technology,and has the characteristics of recyclable electrodes,small footprint,simple preparation process,etc.,which has a better prospect for organic wastewater treatment.In photoelectrocatalytic wastewater treatment technology,the photoelectric anode is the core that determines the photoelectrocatalytic degradation capacity.Most of the photoelectric anodes currently studied have low solar energy utilisation,easy stacking between particles,low loading force and high cost.The preparation of new thin film electrodes with high photocatalytic activity and superior surface loading is a trend in the research and development of photocatalytic technology,which has important economic value and research significance.The investigation of thin film electrodes with ideal solar energy utilisation,good stability and high catalytic activity is a hot research topic in the field of photocatalysis.Bismuth-based semiconductors,with their unique electron layer structure capable of generating photogenerated carriers under visible light conditions,are a semiconductor material with catalytic potential.Among them,bismuth oxide（Bi₂O₃）,due to its simple preparation process,different forbidden band widths and catalytic activity of different crystalline phases,is of great significance to be compounded with other bismuth-based semiconductors to investigate the enhancement of their photocatalytic performance and the modification mechanism.The photocatalytic capability of bismuth oxide photoanodes is severely limited by their narrow response range to visible wavelengths and high photogenerated carrier complexation rates.Therefore,in this study,bismuth oxide was compounded with bismuth-based semiconductors to form heterojunctions to investigate the photocatalytic capability of the composite electrodes.The main research work carried out and relevant conclusions obtained.（1）Bi₂O₃/FTO（BO/FTO）thin film electrodes were prepared by chemical precipitation method with bismuth oxide powder at room temperature,and then Bi₂S₃/Bi₂O₃/FTO（BS/BO/FTO）thin film electrodes were prepared by attaching the powder to the surface of FTO conductive glass by coating method.The structure,morphological characteristics,light absorption performance,energy band structure,etc.of the electrode prepared with formaldehyde have been studied;methylene blue（MB）is the main treatment impurity in the experiment,and metallurgical wastewater containing phenol is inevitable in practical applications.It simulates MB in the sun.Photoelectrocatalytic degradation efficiency under light irradiation.The study shows that the prepared material has high purity and is needle-like bismuth oxide surface loaded with bismuth sulphide particles under microstructure.The films contain Bi,O and S elements,and the photocurrent density and photocatalytic activity of the BS/BO/FTO electrode are better than those of the BO/FTO electrode.the BS/BO/FTO composite electrode has good crystallinity and stability,and the composite of BO and BS can effectively promote the separation of photogenerated electron/hole pairs,so the catalytic activity of the BS/BO/FTO thin film electrode is improved.（2）A three-dimensional spherical shaped Bi₂O₃/Bi₂₈O₃₂（SO₄）₁₀/FTO（BO/BOS/FTO）photoelectrode was prepared by electrodeposition and annealing treatment.The structure,morphological characteristics,light absorption performance,energy band structure,etc.of the electrode prepared with formaldehyde have been studied;methylene blue（MB）is the main treatment impurity in the experiment,and metallurgical wastewater containing phenol is inevitable in practical applications.It simulates MB in the sun.Photoelectrocatalytic degradation efficiency under light irradiation.The results indicated that the photocurrent density and photocatalytic degradation efficiency of BO/BOS/FTO electrodes were improved with the presence of Bi,O and S elements in the films.The capture experiments showed that hydroxyl radicals（-OH）and holes（h⁺）were the main reactants in the degradation process.the BO/BOS/FTO composite electrode had good stability and after four successive degradation cycles,the MB removal rate remained essentially unchanged.The increase of the photoelectrocatalytic ability is attributed to the increase of the visible light excitation range of the BO/BOS/FTO composite film electrode and the formation of heterojunctions.Finally,the charge transfer mechanism of BO/BOS/FTO is also proposed.