Study On Photocatalytic Properties Of Lanthanide Perovskite Oxide-based Composites

Photocatalytic technology is one of the important methods to solve environmental pollution and energy crisis.It can not only generate hydrogen from water,but also effectively decompose organitic contaminants by photocatalytic materials.So far,perovskite oxides have been widely used in photocatalysis,electrocatalysis and energy storage due to their good structure stability and excellent catalytic performance.Among the perovskites,lanthanum nickelate（La Ni O₃）is considered to be a promising photocatalyst due to its non-toxicity,stable structure,wide photoresponse range,and cost-effectiveness.However,the main bottlenecks of the low conduction-band position and high photogenerated carrier recombination efficiency of pure La Ni O₃limit their photocatalytic application.Therefore,in order to enhance the photocatalytic activity of La Ni O₃–based photocatalysts,it is quite effective to modify La Ni O₃by semiconductor recombination or element doping.Interface design and energy band regulation are considered as effective strategies for the separation and transfer of photogenerated carriers in composite photocatalysts.Based on the above research,this paper aims to introduce the construction of heterojunction,co-catalyst effect and cation doping into the La Ni O₃.We constructed two type composite photocatalysts,La Ni O₃/g-C₃N₄/Mo S₂and La Ni_0.8Fe_0.2O₃/g-C₃N₄in this work.Through the regulation of the energy band structure,the separation and transfer of photogenerated charges at the interface are promoted,while retaining the strong redox ability of photogenerated electrons–holes pairs.The specific research contents of this paper are as follows:（1）A novel LaNiO₃/g-C₃N₄/MoS₂ternary composite photocatalysts were fabricated by a simple wet chemical route.Mo S₂flakes co-catalyst were loaded on a hybrid material surface,which was formed by La Ni O₃nanocubes embedded on layered g-C₃N₄,and an excellent heterostructure with multiple contactsites was obtained.Under simulated sunlight irradiation,the photocatalytic hydrogen production rate of ternary composite was 45.1μmol h^-1,which was 19.1 times than that of pure g-C₃N₄and 4.9 times than that of La Ni O₃/g-C₃N₄binary photocatalyst,respectively.In addition,the ternary photocatalyst exhibited excellent photocatalytic performance for both the degradation of antibiotic tetracycline hydrochloride and the reduction of heavy metal ions Cr（VI）under visible light irradiation.Experimental results confirmed that the synergistic effect of the Z-scheme heterojunction（composed by La Ni O₃and g-C₃N₄）and the cocatalyst（Mo S₂）effectively realizes the transfer of photogenerated carriers from"slow transfer"to"high transfer",which promotes photocatalytic hydrogen production and pollutant degradation.（2）A series of Fe-doped LaNi_1-xFe_xO₃samples were prepared by conventional sol-gel accompanied combustion method,and the optimal doping concentration was determined to be 20%(i.e.La Ni_0.8Fe_0.2O₃).Then,the La Ni_0.8Fe_0.2O₃/g-C₃N₄binary composite was prepared by hydrothermal method.The binary photocatalyst exhibited a high rate of 86.1%for TC degradtion within 120 minutes,and a removal rate of98.2%for the Cr（VI）reduction within 60 minutes,and showed excellent cycling stability at the same time.Through XPS,SEM and XRD characterization analysis confirmed that Fe doping will increase the concentration of oxygen vacancies,which is conducive to the formation of electron traps and prolongs the lifetime of photogenerated carriers.UV-Vis DRS,Mott-Schottky and radical trapping experiments showed that the formation of type II heterojunction(composed by La Ni_0.8Fe_0.2O₃and g-C₃N₄)can promote the spatial separation of photogenerated carriers,reduce the recombination of photogenerated electron–hole pairs,and further improve the photocatalytic activity of the binary composites.