Aurivillius Oxides Nanosheets-Based Photocatalysts for Efficient Oxidation of Malachite Green Dye

Abstract

Aurivillius oxides ferroelectric layered materials are formed by bismuth oxide and pseu-do-perovskite layers. They have a good ionic conductivity, which is beneficial for various photo-catalyzed reactions. Here, we synthesized ultra-thin nanosheets of two different Aurivillius oxides, Bi2WO6 (BWO) and Bi2MoO6 (BMO), by using a hard-template process. All materials were characterized through XRD, TEM, FTIR, TGA/DSC, DLS/ELS, DRS, UV-Vis. Band gap material (Eg) and potential of the valence band (EVB) were calculated for BWO and BMO. In contrast to previous reports on the use of multi composite materials, a new procedure for photocatalytic efficient BMO nanosheets was developed. The procedure, with an additional step only, avoids the use of composite materials, improves crystal structure, and strongly reduces impurities. BWO and BMO were used as photocatalysts for the degradation of the water pollutant dye malachite green (MG). MG removal kinetics was fitted with Langmuir—Hinshelwood model obtaining a kinetic constant k = 7.81 × 10−2 min−1 for BWO and k = 9.27 × 10−2 min−1 for BMO. Photocatalytic dye degradation was highly effective, reaching 89% and 91% MG removal for BWO and BMO, respectively. A control experiment, carried out in the absence of light, allowed to quantify the contribution of adsorption to MG removal process. Adsorption contributed to MG removal by a 51% for BWO and only by a 19% for BMO, suggesting a different degradation mechanism for the two photocatalysts. The advanced MG degradation process due to BMO is likely caused by the high crystallinity of the material synthetized with the new procedure. Reuse tests demonstrated that both photocatalysts are highly active and stable reaching a MG removal up to 95% at the 10th reaction cycle. These results demonstrate that BMO nanosheets, synthesized with an easy additional step, achieved the best degradation performance, and can be successfully used for environmental remediation applications.

Enhanced Photocatalytic Properties of Restacked Unilamellar [SrTa2O7]2– Nanosheets of Aurivillius Phase Layered Perovskites

“…A survey of the previous literature on photocatalytic characteristics of Aurivillius perovskites indicates that the morphology/structure of the reported Aurivillius perovskites is multilayered or sheet-like; more specifically, the Bi 2 O 2 interlayers still remained between the perovskite layers; in technical parlance, they are not exfoliated and cannot be considered single perovskite 2D nanosheets. , In comparison to the previous reports on Aurivillius phase perovskites, our three-step intercalation process not only produces unilamellar nanosheets but also yields larger nanosheets in size (50 nm–1 μm). ,,− The main objective of this work was to develop an efficient procedure for the exfoliation of Aurivillius perovskites and to evaluate the photocatalytic activity of the restacked [SrTa 2 O 7 ] 2– nanosheets for the hydrogen evolution reaction and degradation of Rhodamine B dye. Additionally, the study aimed to determine the extent of improvement in photocatalytic activity resulting from the structural manipulation by examination of the original layered structure (Bi 2 SrTa 2 O 9 ) activity under the studied photocatalytic conditions.…”

“… 16 , 33 In comparison to the previous reports on Aurivillius phase perovskites, our three-step intercalation process not only produces unilamellar nanosheets but also yields larger nanosheets in size (50 nm–1 μm). 21 , 23 , 34 − 36 The main objective of this work was to develop an efficient procedure for the exfoliation of Aurivillius perovskites and to evaluate the photocatalytic activity of the restacked [SrTa 2 O 7 ] 2– nanosheets for the hydrogen evolution reaction and degradation of Rhodamine B dye. Additionally, the study aimed to determine the extent of improvement in photocatalytic activity resulting from the structural manipulation by examination of the original layered structure (Bi 2 SrTa 2 O 9 ) activity under the studied photocatalytic conditions.…”

Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6-CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation

“…The potentials of E CB and E VB of p-CuO, n-Bi 2 O 2 CO 3 , n- Bi 2 MoO 6 , and p–n–n heterojunction (Pd/BM-BOCC) have been calculated by the following equations E CB = χ − E normalc − 0.5 0.25em E normalg E VB = E CB + E normalg where E c and χ are the free electronic energy on the NHE scale (about 4.5 eV) and absolute electronegativity, respectively, and E CB and E VB are the conduction and valence band edge potential, respectively. The χ values (obtained from the literature) for Bi 2 MoO 6 , Bi 2 O 2 CO 3 , and CuO are about 6.13, 6.35, and 5.89 eV, respectively. ,, Based on the above-mentioned equations, the top of VBs lies at 2.72, 3.05, and 2.20 V and the corresponding bottom of CB values is 0.54, 0.65, and 0.59 V, respectively, for Bi 2 MoO 6 , Bi 2 O 2 CO 3 , and CuO in the Pd/BM-BOCC composite.…”

“…CB and E VB are the conduction and valence band edge potential, respectively. The χ values (obtained from the literature) for Bi 2 MoO 6 , Bi 2 O 2 CO 3 , and CuO are about 6.13, 6.35, and 5.89 eV, respectively 58,79,80. Based on the abovementioned equations, the top of VBs lies at 2.72, 3.05, and 2.20 V and the corresponding bottom of CB values is 0.54, 0.65, and 0.59 V, respectively, for Bi 2 MoO 6 , Bi 2 O 2 CO 3 , and CuO in the Pd/BM-BOCC composite.The photoexcited electron−hole pair transfer and separation efficiency were elucidated by PL spectra in FigureS4c.…”

Bismuth-Based Z-Scheme Heterojunction Photocatalysts for Remediation of Contaminated Water

“…Additionally, the small optical band gaps of specific Aurivillius structures enable them to absorb visible light efficiently. 67 Another class of bismuth-based structures is the Sillen-Aurivillius phases, as shown in Figure 2c. These are layered oxyhalide materials with a general formula of…”