Study On The Preparation And Properties Of Perovskite Photocatalysts

Photocatalytic technology is known as the protentialtechnology to solve the energy crisis in 21 st century. Perovskite hasexcellent ferroelectric, piezoelectric, optical properties which are widely used in the world.With good optical and electrical properties, NaNbO₃, Bi2WO₆, SrTiO₃ photocatalysts have typical perovskite-type structures. So we want to enhance the potocatalytic activity of these photocatalysts by complex modification. The maincontentsand resultsare asfollows:1.The NaNbO₃-Ba₄SrNb₄O₁₅ heterojunctionsachieved by one-step hydrothermalmethod.Thecharacterization of the photocatalysts were probed byXRD,FE-SEM,BETandUV-VISet al.Theresultsshowed thatthe NaNbO₃-Ba₄SrNb₄O₁₅ heterojunctions are composed of flake Ba₄SrNb₄O₁₅ and granular NaNbO₃. Theabsorptionedgeof the heterojunctions expands tovisiblelight range.The sample has thehighestspecificsurfacearea, ptotocatalytic performance and lowest band gap 3.02 eV, which was prepared by hydrothermal process in 250°C. The yield of hydrogen is 1.021 umol by 0.1 g sample with methanolassacrificialreagents under visible light irradiation within 2 hours.2.The Bi2WO₆-SrTiO₃ heterojunctions achieved by two-step hydrothermalmethod.Firstly, SrTiO₃ was synthesized by hydrothermal method in 200°C. Then, Bi2WO₆ was growing on the surface of SrTiO₃ to achieve Bi2WO₆-SrTiO₃ heterojunction by hydrothermal method in 180°C. The samples werecharacterized by XRD,FE-SEM,BETandUV-VIS etc in detail.Theresults showed thattheflake Bi2WO₆ grows on the surface of SrTi O₃. The aggregationstate of samples was changed from roseshapetoaball structure withtheincrease of SrTiO₃ amount. At the same time, the number of globularpolymerdecreased, the diameter of globularpolymer reduced, and the specificsurfaceareaincreased. The absorption edge of Bi2WO₆-SrTiO₃ heterojunction is bigger than that of Bi2WO₆, and the band gap reduced from2.82to2.69 eV. The Bi2WO₆-SrTiO₃ heterojunction showed thestrongestmethylorangedyeadsorption performance which was prepared by SrTiO₃ and Bi2WO₆ with theratioof3:1. Whenthe ratioturn to 3:5, the Bi2WO₆-SrTiO₃ heterojunction showed thehighestphotocatalyticactivity.3.The SrTiO₃-x was prepared by Ti³⁺ self-doped with TiCl₃,SrCl₂·6H₂O,H₂O₂ asreactants at 1200°Cusing H₂O₂ toadjust Ti³⁺dopingamount.The samples werecharacterized by XRD,FE-SEM,BETandUV-VIS etc in detail.Theresultsshowed that the lattice structure of the Ti³⁺ self-dopedSrTiO₃-xslightly distorted. The Ti³⁺ ions and alargenumber ofoxygenvacancies were probed by XPS. Theabsorption edge of the catalyst expanded intovisiblelight range. The band gap of SrTiO₃-xwas decreased from 3.18 to 2.88 eV. The sample prepared with 10 %H₂O₂（with the molar equivalent of TiCl₃） showed thehighestphotocatalyticperformance inthe degradationofrhodamineBunder visible light irradiation. After loading NiO by impregnationmethod, the band gap of NiO-SrTiO₃-x reducedfrom2.95to2.38 eV, and the photocatalyticperformance of NiO-SrTiO₃-x increased3.5timesthan that of SrTiO₃-x.