Microwave-assisted Hydrothermal Synthesis Of LaFeO 3 Photocatalyst And Its Photocatalytic Properties

Perovskite-type composite oxide is widely used as a catalyst because it has unique physical properties such as light,electricity,magnetic,heat and other chemical properties such as oxidation and reduction,activated adsorption molecules.In this paper,LaFeO₃ and LaFe_1-xCo_xO₃ photocatalysts were synthesized by microwave-assisted hydrothermal method.The prepared samples were characterized by SEM,XRD,DSC-TG,FI-TR and TEM.The photocatalytic activity of LaFe_1-xCo_x O₃ and LaFeO₃ were studied,the main contents and the results obtained are as follows:1)The photocatalyst of La FeO₃ with hollow porous structure was synthesized by microwave-assisted hydrothermal method using ammonia as precipitant and glucose as template.The influences of different precipitants,pH value,reaction temperature,reaction time,glucose concentration,ethylenediamine content and dispersant on the morpHology and size of LaFeO₃ were investigated.The results showed that the optimum conditions were 7 of pH value,reaction temperature was 170 ℃,reaction time was 4 hours,glucose concentration was 0.3 mol/ L and ethylenediamine was 0.5 mL.Dispersant polyethylene glycol 2000 and polyvinylpyrrolidone have little effect on the dispersibility of La Fe O₃.Ethylenediamine content and glucose concentration have a great influence on the morphology of LaFeO₃ catalyst,and when the amount of ethylenediamine is low or higher,the specific surface area decreases.The results of differential thermal-thermogravimetric showed that when the temperature reaches 800 ℃,there is no weight loss,indicating that the thermal decomposition at this temperature is complete,sothe roasting temperature should be higher than 800 ℃.The La FeO₃ catalyst was prepared by the comparison of surface area and pore size.The pore size of the La FeO₃ catalyst was mainly macroporous and mesoporous.When the pH value was 8.95 and the amount of ethylenediamine was 0.5 m L,the specific surface area was 18.5800 m2 / g,it is clear that the specific surface area will be greater when the pH is 6.98 and the amount of ethylenediamine is 0.5 mL.The results of photocatalytic performance show that the photocatalytic degradation rate reached 99.86% after 1 hour of light and ethylenediamine content is 0.5 mL when the other conditions are the same.The degradation rates were 66.44% and 82.95% when the amount of ethylenediamine is 0.25 mL and 1.0 mL,respectively.2)La Fe_1-xCo_xO₃ photocatalyst was prepared by doping Co ions on the basis of LaFeO₃ photocatalyst.The influences of doping amount and roasting temperature on the morphology of LaFe_1-xCo_xO₃ photocatalyst were studied.The results showed that the particle size of the LaFe_1-xCo_xO₃ photocatalyst decreases with the increase of the doping amount and finally basically remain unchanged basically,the dispersion is getting worse with the increase of the doping amount.When the roasting temperature is 800 ℃,the LaFe_1-xCo_xO₃ photocatalyst with fine hollow structure is obtained.XRD analysis of the doping amount of Co showed that the doping of cobalt ions don’t change the crystal structure,but get into the lattice instead,it still orthorhombic perovskite structure.The photocatalytic degradation of La Fe_1-xCo_xO₃ photocatalyst with different amount of Co ions was studied.The results showed that the photocatalytic activity was higher than that of undoped when the doping amount was 0.1.The degradation rate of degraded methylene blue was as high as 96.83% when 30 minutes of light,while the degradation rate of La FeO₃ without Co was 83% under the same irradiation time.As the doping amount continues to increase,the photocatalytic activity decreases gradually.