The Preparation And Photocatalytic Performances Of LaFeO₃-based Nanocomposites

As one of the green and efficient renewable energy,solar energy can be used as an effective substitute for fossil fuels.Photocatalytic technology can convert solar energy into chemical energy by semiconductor materials under normal temperature and pressure,which has become a hot research topic in the field of material science preface.Perovskite oxide with narrow band gap can be excited by visible light,which has excellent physical and chemical properties and is easy to adjust the microstructure,and is one of the most promising photocatalytic materials.In view of the above problems,this paper takes the perovskite structure oxide lanthanum ferrite（LaFeO₃）as the research object,and modifies it by constructing heterojunctions,composite co-catalysts,and adjusting morphology to prepare composite catalysts with high visible light response,and studies its photocatalytic performance enhancement mechanism.The main research work of this paper is as follows:（1）A ternary nanocomposite Ag/g-C₃N₄/LaFeO₃ based on heterojunction and co-catalyst double modification was designed.Compared with pure LaFeO₃,the composite has higher redox potential,which increases the distance between photogenerated electrons and holes and inhibits the rapid recombination of photogenerated carriers.The localized surface plasmon resonance effect of the metal-assisted catalyst promotes the absorption of visible light by the composite material,so that it exhibits excellent photocatalytic degradation effect on methylene blue（MB）and tetracycline hydrochloride（TC）under visible light irradiation.The reaction kinetic constants are 4.81 and 3.88 times of those of pure LaFeO₃.In addition,ternary nanocomposites showed excellent cycling stability in three consecutive degradation cycles.（2）p-n heterojunction is composed ofα-Fe₂O₃/LaFeO₃,the Z-scheme heterojunction is composed of LaFeO₃/g-C₃N₄ and the Schottky-junction is composed of g-C₃N₄/Ti₃C₂.The band structure of semiconductor materials was adjusted by the synergistic effect of the three heterojunctions,so as to realize the regulation of the photo-generated carrier transmission mechanism of the composites.The results show that the composite material α-Fe₂O₃/LaFeO₃/g-C₃N₄/Ti₃C₂（FLCT）has the largest reaction kinetics constants for the degradation of MB,Rhodamine B（Rh B）,TC and reduced hexavalent chromium（Cr （VI））,which are 3.41,3.86,5.44 and 4.14 times of that of pure LaFeO₃,respectively. α-Fe₂O₃/LaFeO₃accelerates the migration of carriers.The presence of g-C₃N₄ makes electrons move to Ti₃C₂,and Ti₃C₂ replaces precious metals as electron traps to capture electrons,thereby inhibiting the recombination of photogenerated electrons and holes.The excellent pollutant degradation activity of FLCT provides a new possibility for the application of photocatalytic technology in water pollution control.（3）Mesoporous LaFeO₃ with hexagonal pore structure was synthesized using mesoporous molecular sieve SBA-15 as the hard template,and ultrathin nanosheets Zn In₂S₄ were grown on the surface of mesoporous LaFeO₃ by hydrothermal method to construct Z-scheme heterojunction M-LaFeO₃/Zn In₂S₄.The specific surface area of the heterojunction composite is 167.4 m² g^-1,which has the best degradation activity of Rh B.The reaction kinetic constant is 26.98 times of that of pure LaFeO₃,and the photocatalytic hydrogen production rate is 540.49μmol h^-1 g^-1.The composite materials increased the specific surface area of pure phase LaFeO₃,increased the number of active sites,and made the electron transition to the Zn In₂S₄ conduction band with negative conduction band position by band regulation,which improved the reduction potential of the catalyst and inhibited the rapid recombination of electrons and holes,thus significantly improving the photocatalytic activity of the composite materials.