Solution Combustion Synthesis Of BiOCl-based Nanocomposites Structure Control And Photocatalytic Properties

“Carbon neutral”requires people to transition from the fossil energy era to the new energy era to reduce carbon emissions.Semiconductor photocatalysis technology can convert solar energy into chemical energy,and realize green applications,such as water decomposition for hydrogen production,CO₂ reduction,degradation of pollutants in water,photovoltaic cells and so on.BiOCl photocatalyst with Sillen layered structure and indirect electron transition mode,which can accelerate the migration of photogenerated carriers and exhibits excellent photocatalytic activity.However,BiOCl is a wide band gap(3.4 eV)semiconductor,which absorbs only 5%of the ultraviolet light of solar energy,making it difficult to make full use of light.To expand the optical absorption range of BiOCl,enhance the migration of photo generated carriers and further improve its photocatalytic activity,a green,low-cost solution combustion synthesis method which can rapidly prepare nano powder was used to modify BiOCl through four strategies:morphology control,heterojunction construction,Fe(?)doping and Bi metal loading.(1)BiOCl photocatalyst was synthesized by solution combustion synthesis method(SCS)and spray solution combustion synthesis method(SSCS),respectively.The results of SEM and TEM show that SCS-BiOCl presented irregular rod-like aggregation morphology,while SSCS-BiOCl exhibited hollw porous microspheres assembled by monolayer nanocrystals(10?20 nm).The BET results show that the hollow porous spherical BiOCl retains the high specific surface area(15.33 m²/g)of the nanocrystals.SSCS-BiOCl microspheres have lower photoelectron recombination rate and better photocatalytic performance.The degradation rate of BiOCl obtained by RhB reaches98%after 60 min of illumination,which is 3 times of that of BiOCl prepared by SCS.(2)Bi₂O₃/BiOCl heterojunction photocatalyst was prepared by NaOH reaction treatment of BiOCl microspheres synthesized in SSCS.XRD results show that with the increase of NaOH solution treatment time,the phase structure of the product changes from BiOCl to Bi₂O₃/BiOCl,and then to Bi₂O₃.Micro morphology analysis showed that Bi₂O₃ nanorods were formed on the surface of the spherical shell after 10 min soaking in NaOH solution.With the prolongation of soaking time,the surface morphology of the products gradually changed from spherical shell to micro rod.The heterojunction sample treated with NaOH solution for 10 min showed better adsorption(19%)and photodegradation properties(93%30 min)for RhB.(3)Fe(?)-doped BiOCl materials were prepared by solution combustion synthesis using ferric nitrate as iron source.According to the results of XRD and XPS,Fe³⁺successfully enters into the BiOCl lattice and produces defects.The optical absorption range of Fe(?)-BiOCl is extended from ultraviolet to visible,the band gap is narrowed(1.35 EV),and the recombination rate of photogenerated electrons and holes is lower than that of pure BiOCl.After Fe(?)doping,BiOCl changed from irregular nanorods to nano flakes and small particles,and its specific surface area increased from 5.11m²·g^-1 to 9.62 m²·g^-1.EDS analysis shows that Fe element is uniformly distributed on BiOCl.Fe(?)-BiOCl has excellent photodegradation performance for RhB,in which the degradation rate of Fe(?)-BiOCl reaches 96%after 60 min of visible light irradiation,which is 4 times of that of pure BiOCl.(4)Bi/BiOCl composites were successfully prepared by solution combustion synthesis using a mixture of fuel(tartaric acid and glycine).The effects of fuel type and reactant ratios on combustion process,product structure,microstructure,optical properties and photocatalytic performance of the product were studied.When the fuel was changed from glycine to a mixed fuel,the phase structure of the product changed from BiOCl to Bi/BiOCl.The ignition temperature of combustion reaction is similar,but the maximum temperature of the synthesis of Bi/BiOCl(540?)is lower than that of BiOCl(732?).The surface plasmon resonance(SPR)effect of Bi particles can effectively separate the photogenerated electron hole pairs,accelerate the interface charge transfer rate,and broaden the light absorption range of Bi/BiOCl composites.Bi/BiOCl composites show excellent photodegradation performance,in which the degradation rate of RhB reaches 98%after simulated light irradiation for 120 min,which is significantly higher than that of pure BiOCl,and the photocatalytic performance of Bi/BiOCl composites is still stable after 6 cycles.There are 53 figures,7 tables and 124 references in this paper.