Synthesis of Hollow Flower-Like Fe3O4/MnO2/Mn3O4 Magnetically Separable Microspheres with Valence Heterostructure for Dye Degradation

Abstract

In this manuscript, hollow flower-like ferric oxide/manganese dioxide/trimanganese tetraoxide (Fe3O4/MnO2/Mn3O4) magnetically separable microspheres were prepared by combining a simple hydrothermal method and reduction method. As the MnO2 nanoflower working as precursor was partially reduced, Mn3O4 nanoparticles were in situ grown from the MnO2 nanosheet. The composite microspheres were characterized in detail by employing scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), vibration sample magnetometer (VSM) and UV–visible spectrophotometer (UV–vis). Under visible light conditions, the test for degrading rhodamine B (RhB) was used to verify the photocatalytic activity of the photocatalyst. The results showed that the efficiency of the Fe3O4/MnO2/Mn3O4 photocatalyst in visible light for 130 min is 94.5%. The catalytic activity of photocatalyst far exceeded that of the Fe3O4/MnO2 component, and after four cycles, the catalytic performance of the catalyst remained at 78.4%. The superior properties of the photocatalyst came from improved surface area, enhanced light absorption, and efficient charge separation of the MnO2/Mn3O4 heterostructure. This study constructed a green and efficient valence heterostructure composite that created a promising photocatalyst for degrading organic contaminants in aqueous environments.

Probing the meta-stability of oxide core/shell nanoparticle systems at atomic resolution

“…In this work, we present an atomic resolution live (in-situ) study of electron beaminduced transformations in core/shell Fe3O4/Mn3O4 and Mn3O4/Fe3O4 nanoparticles by means of high-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy (STEM-EELS). Interestingly, the manganese oxideiron oxide nanoparticles system is appealing not only for its unique magnetic properties (e.g., antiferromagnetic interface coupling or magnetic proximity effects) [10,[38][39][40] but also for its applications in diverse fields like catalysis and environmental remediation [41,42], batteries and supercapacitors [43,44], microwave components [45] or biomedicine [46,47]. Our results, acquired within time scale of minutes, show that the nanoparticles under electron irradiation can develop a variety of defects, including formation of voids and dislocations, as the Mn3O4 component is forced to reduce to MnO.…”

Facile Construction of Zn‐Doped Mn3O4−MnO2 Vertical Nanosheets for Aqueous Zinc‐Ion Battery Cathodes

“…It has been demonstrated that the binding energy of Mn 4+ ions in MnO 2 for the Mn 2p 3/2 level is at 642.4–642.8 eV, while the lower oxidation states of Mn 2 O 3 , Mn 3 O 4 and MnO are located in the range of 640.8–641.6 eV [39] . Therefore, the three pairs of doublets with the doublet at 640.9/652.7 eV, 641.8/653.7 eV, and 642.9/654.6 eV can be ascribed to the Mn 2+ , Mn 3+ , and Mn 4+ according to the reported work, implying that the as‐synthesized ZnMM‐NSs sample contains multivalent state manganese (Mn(II), Mn(III), and Mn(IV)) [40–41] . In addition, the energy separation between two peaks of Mn 3 s core level spectrum can be used to determine the mean manganese oxidation state of manganese oxides [22] .…”

“…[39] Therefore, the three pairs of doublets with the doublet at 640.9/652.7 eV, 641.8/653.7 eV, and 642.9/654.6 eV can be ascribed to the Mn 2 + , Mn 3 + , and Mn 4 + according to the reported work, implying that the assynthesized ZnMM-NSs sample contains multivalent state manganese (Mn(II), Mn(III), and Mn(IV)). [40][41] In addition, the energy separation between two peaks of Mn 3 s core level spectrum can be used to determine the mean manganese oxidation state of manganese oxides. [22] The peak separation is 5.16 eV (Figure 3c), suggesting that the Mn oxidation states of as-prepared ZnMM-NSs is ca.…”