Krasnov Aleksei G, Napalkov Maxim S, Vlasov Maxim I, Koroleva Mariia S, Shein Igor R, Piir Irina V
Institute of Chemistry, Federal Research Center Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia.
Syktyvkar State University, Syktyvkar, Russia.
Inorg Chem. 2020 Sep 8;59(17):12385-12396. doi: 10.1021/acs.inorgchem.0c01472. Epub 2020 Aug 10.
The photocatalytic properties of BiTiO ( = 0, 0.5) pyrochlores are examined via calculations and experiments. A coprecipitation method is applied for the synthesis of nanopowder pyrochlores. The pyrochlore phase formation starts at 500 °C (BiTiO) and 550 °C (BiTiO). Nanopowders are found to be a metastable character of pyrochlore phases. The presence of bismuth and oxygen vacancies enhances the thermal stability of the BiTiO phase in comparison with the BiTiO phase. The estimated crystallite size is 30-40 nm with noticeable agglomerates of about 100-300 nm according to scanning electron microscopy (SEM) and with the formation of particles (510-580 nm) in the aqueous medium. The isoelectric points of the nanopowders seem to be shifted to the strongly acidic region, resulting in the formation of negative surface particle charges of -33 mV (BiTiO) and -27 mV (BiTiO) at pH 5.88 in distilled water. The specific surface area is 11.5 m/g (BiTiO) and 12.00 m/g (BiTiO). The use of the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional allows achieving an excellent agreement between theoretical and experimental structural parameters. The screened Coulomb hybrid HSE03 functional is the most appropriate for describing the optoelectronic properties. Bismuth titanate pyrochlores are wide-gap semiconductors with strong abilities to be active photocatalysts under visible irradiation. The optical values for direct/indirect transition according to the experiment, 3.19/2.94 eV ( = 0) and 3.24/3.03 eV ( = 0.5), and the DFT/HSE03 calculations, 2.92/2.87 ( = 0) and 3.42/- eV ( = 0.5), are in the visible light region and are close. The calculated low effective masses of the charge carriers and suitable band edge positions confirm the ability of the pyrochlores to act as photocatalysts. The photocatalytic activity has been evaluated through the decomposition of rhodamine B under visible irradiation. BiTiO shows the highest activity in comparison with BiTiO, which is in good agreement with theoretically predicted and experimentally revealed characteristics.
通过计算和实验研究了BiTiO（= 0, 0.5）烧绿石的光催化性能。采用共沉淀法合成纳米粉末烧绿石。烧绿石相的形成始于500°C（BiTiO）和550°C（BiTiO）。发现纳米粉末具有烧绿石相的亚稳特性。与BiTiO相比，铋和氧空位的存在增强了BiTiO相的热稳定性。根据扫描电子显微镜（SEM），估计的微晶尺寸为30 - 40 nm，有明显的约100 - 300 nm的团聚体，并且在水介质中形成了颗粒（510 - 580 nm）。纳米粉末的等电点似乎向强酸性区域移动，导致在蒸馏水中pH为5.88时表面颗粒带负电荷，BiTiO为 - 33 mV，BiTiO为 - 27 mV。比表面积分别为11.5 m²/g（BiTiO）和12.00 m²/g（BiTiO）。使用具有Perdew - Burke - Ernzerhof（PBE）泛函的广义梯度近似（GGA）能够使理论和实验结构参数之间达成极好的一致性。筛选后的库仑杂化HSE03泛函最适合描述光电性质。钛酸铋烧绿石是宽禁带半导体，在可见光照射下具有很强的活性光催化能力。根据实验，直接/间接跃迁的光学值为3.19/2.94 eV（= 0）和3.24/3.03 eV（= 0.5），以及DFT/HSE03计算值为2.92/2.87（= 0）和3.42 / - eV（= 0.5），都在可见光区域且相近。计算得到的低有效质量的电荷载流子和合适的能带边缘位置证实了烧绿石作为光催化剂的能力。通过在可见光照射下罗丹明B的分解来评估光催化活性。与BiTiO相比，BiTiO表现出最高的活性，这与理论预测和实验揭示的特性高度一致。
