当前位置: X-MOL 学术Dalton Trans. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Coupled-substituted double-layer Aurivillius niobates: structures, magnetism and solar photocatalysis.
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-01-09 , DOI: 10.1039/c9dt04339j
Sonia Rani 1 , Gollapally Naresh , Tapas Kumar Mandal
Affiliation  

Development of layered perovskites for sunlight-driven catalysis has gained a lot of attention in contemporary inorganic materials research. While the compositional modifications of three-dimensional perovskites are ubiquitous, they are infrequent in the case of layered perovskites particularly with niobates when the perovskite layer thickness is low. We report here the solid state synthesis of a series of lead-free double-layer Aurivillius niobates, LaBi2Nb1.5M0.5O9 (M = Cr, Mn, Fe, Co), by adopting a heterovalent coupled substitution strategy with SrBi2Nb2O9. Rietveld structure refinements of the compounds using P-XRD data suggest the formation of 3dn transition metal incorporated double-layer Aurivillius niobates in the non-centrosymmetric A21am space group, isostructural with the parent. The compounds show optical absorption in the visible region with the absorption tail extending up to ∼650 nm and band gaps ranging from 2.25-2.94 eV. While the compounds show paramagnetic behaviour with no indication of magnetic phase transition or ordering in the temperature range 5-300 K, the Mn compound stabilizes with a low-spin (LS) configuration in contrast to all others (Cr, Fe and Co compounds), which adopt a high-spin (HS) configuration. The stabilization of the LS configuration (t42g) of the Mn compound occurs with eg → t2g electron redistribution due to the suppression of first-order Jahn-Teller (FOJT) distortion by the dominating second-order Jahn-Teller (SOJT) distortion of Nb5+ (4d0). The compounds exhibit photocatalytic rhodamine B degradation at pH 2 within 50-110 minutes under natural sunlight-irradiation and remain stable after five consecutive degradation cycles maintaining their activity largely intact. The heterovalent coupled substitution strategy adopted here will open up possibilities for transforming many other UV-active layered niobates into sunlight-active compounds without using toxic Pb or expensive Ag, while the paramagnetic nature of the compounds will be helpful in post-catalytic magnetic separation of the catalysts. It is believed that the electronic instability of the t32ge1g configuration of Mn due to competing FOJT and SOJT effects may have far-reaching consequences in modifying its magneto-structural and electron transport properties.

中文翻译:

偶合取代的双层Aurivillius niobates:结构,磁性和太阳光催化作用。

层状钙钛矿用于阳光驱动催化的研究在当代无机材料研究中引起了很多关注。尽管三维钙钛矿的组成改性是普遍存在的,但在钙钛矿层厚度低时,在层状钙钛矿尤其是铌酸盐的情况下,它们很少出现。我们在这里报告通过采用SrBi2Nb2O9的异价偶联取代策略,对一系列无铅双层铌酸奥利奇柳酸盐LaBi2Nb1.5M0.5O9(M = Cr,Mn,Fe,Co)进行固态合成。使用P-XRD数据对化合物的Rietveld结构进行的改进表明,在非中心对称的A21am空间群中,与母体同构的3dn过渡金属结合的双层Aurivillius niobates的形成。这些化合物在可见光区域显示出光吸收,吸收尾部延伸至约650 nm,带隙范围为2.25-2.94 eV。尽管这些化合物在5-300 K的温度范围内表现出顺磁行为,但没有磁性相变或有序的迹象,但与所有其他化合物(Cr,Fe和Co化合物)相比,Mn化合物以低旋转(LS)构型稳定。 ,采用高旋转(HS)配置。Mn化合物的LS构型(t42g)的稳定发生在→→t2g电子再分布的情况下,这归因于Nb5 +的主要二阶Jahn-Teller(SOJT)畸变抑制了一阶Jahn-Teller(FOJT)畸变。 (4d0)。该化合物在自然阳光照射下于50-110分钟内在pH 2下显示出光催化的若丹明B降解,并在五个连续的降解循环后保持稳定,并在很大程度上保持其活性。此处采用的异价偶联取代策略将为将许多其他具有紫外线活性的层状铌酸盐转变为具有日光活性的化合物提供可能性,而无需使用有毒的Pb或昂贵的Ag,而这些化合物的顺磁性质将有助于催化后分离磁性化合物。催化剂。据信,由于竞争的FOJT和SOJT效应,Mn的t32ge1g构型的电子不稳定性可能会在改变其磁结构和电子传输特性方面产生深远的影响。
更新日期:2020-02-10
down
wechat
bug