| Lanthanide compounds exhibit unique optical, electritical, magnetical and chemical properties arising from their 4f electrons. NaLaTi2O6 and La(OH)3 as typical lanthanide titanate and hydroxide materials, the hydrothermal synthesis methods and properties exploration were the main theme of our research.In this work, NaLaTi2O6, La(OH)3 and NaLaTi2O6-La(OH)3 composite were prepared through hydrothermal methods using La(NO3)3 as lanthanum source, butyl titanate or Ti(SO4)2 as titanium source, NaOH or divinyl three amine (DETA) as alkali source. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy. The results show that:Pure NaLaTi2O6 was synthesized via hydrothermal method at 200 ℃ for 24 h with Ti(SO4)2 as titanium source. It is found that the solvent polarity strongly influences the morphologies of NaLaTi2O6, four different morphologies (nanosheet, globular, block and filamentous) were obtained with the reduction of solvent polarity. Nanosheet NaLaTi2O6 exhibits preferable photocatalytic activity, for the decomposition of MB, the decomposition ratio is 98.5% after 60 min ultraviolet light irradiation. Nanoparticle NaLaTi2O6 was fabricated by the hydrothermal process with butyl titanate as titanium source followed by a calcination process at 800 ℃. The NaLaTi2O6 with the minimum particle size was prepared when the NaOH concentration was 1.5 mol/L in precursors, and it shows the best photocatalytic activity, the corresponding decomposition rate of MB is 80.5% in 60 min under ultraviolet light.The electrochemical performances of NaLaTi2O6 were also studied. NaLaTi2O6 displays excellent rate capability and outstanding cyclic stability. In the process of the current density increase from 20 mA/g to 400 mA/g, the specific capacity of NaLaTi2O6 decreases gradually (a capacity of 125 mAh/g and 92 mAh/g at 20 mA/g and 400 mA/g, respectively), and the capacity is then reversibly back to 122 mAh/g once the current density is set back to 20 mA/g again with 97.6% capacity retention of initial capacity. Moreover, the capacity of NaLaTi2O6 shows a sustained upward trend with the increase of charge-discharge cycles. The discharge capacity at 750 th cycles can reach 180 mAh/g and this value maintains to 950 th cycles. After 1000 cycles, its capacity is still as large as 165 mAh/g.Pure La(OH)3 were synthesized at 200 ℃ for 2-24 h using La(NO3)3 as lanthanum source, NaOH or divinyl three amine (DETA) as the alkali source. The La(OH)3 nanorod, which prepared at 200 ℃ for 12 h with NaOH as alkali source shows a better photocatalytic activity, the decomposition rate for RhB is 80% after irradiation for 60 min under ultraviolet light. It is found that modifying La(OH)3 with Ag, improved the photocatalytic activity of La(OH)3. When the doping amount of Ag is 4 wt%, the degradation rate for RhB can reach 83% after visible light irradiation for 6 h.NaLaTi2O6-La(OH)3 composite were successfully fabricated by the hydrothermal methods at 200 ℃ for 24 h taking La(NO3)3 as lanthanum source, Ti(SO4)2 as titanium source. The composite reveals an improvement over NaLaTi2O6 and La(OH)3 in photocatalytic activity under ultraviolet light, the corresponding decomposition ratios of MB is 89.6% in 60 min. Polarity solvent has an important effect on the photocatalytic performance of NaLaTi2O6-La(OH)3 composite. The sample obtained with the volume ratio of ethanol/water is 1:3 in precursor exhibits a much higher photocatalytic activity, the decomposition ratios of MB is 95.9% in 60 min under ultraviolet light. |
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