Fabrication, In-Depth Characterization, and Formation Mechanism of Crystalline Porous Birnessite MnO₂ Film with Amorphous Bottom Layers by Hydrothermal Method

Abstract

Hydrated porous birnessite MnO2 films were prepared on Si substrates and characterized in-depth by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The as-prepared film is composed of a well-crystallized porous surface layer and one or more amorphous bottom layers. The morphology and structure of the film can be understood by the combined action of internal stress and conversion of the porous surface layer. The dynamic process of formation and conversion in the growth of porous surface layer is pointed out, which shows the transformation of reactants to amorphous bottom layers via the formation and conversion process of the porous surface layer. This result is of significant importance for increasing the utilization ratio of materials and for understanding basic physical and chemical processes of manganese oxide film growth under hydrothermal conditions.

Mixed-Phase Manganese Dioxide and Functionalized Graphite Supported Platinum/Manganese Dioxide Catalyst for Light-Driven Photoelectrochemical Cell

“…When the precursor concentration is decreased, the pore density increases and pore size decreases as illustrated in Figure 2b and 2c. According to the literature reported by Yan et al, 26 the porous chemically grown feature may be attributed to the coulombic interaction between SO 4 2− anions, pyrolusite MnO 2 nanosheets with negative surface charge, and polar H 2 O molecules. In sum, the results described above show qualitatively that the sub-micropores were well-dispersed on the MnO 2 powder for sample C. Figure 3 shows the use of X-ray powder diffraction to observe the crystal structure of the MnO 2 photocatalyst powder prepared from 0.5M to 0.1M precursor concentrations.…”

Hydrothermal synthesis of MnO2/CNT nanocomposite with a CNT core/porous MnO2 sheath hierarchy architecture for supercapacitors

“…In order to achieve high capacitive performance, a large surface area and a fast ion/electron transport of the electrode material are required. Therefore, extensive research has been focused on the synthesis of nanostructured MnO 2 as the nanoscale powder, which provides not only a high specific surface area, but also a fast ion and electron transport [16-25]. Various forms of MnO 2 including one-dimensional (nanorods, nanowires, nanobelts, nanotubes) [16-22], two-dimensional [2-D] (nanosheets, nanoflakes) [23-25], and three-dimensional [3-D] (nanospheres, nanoflowers) [26-28] nanostructures have been synthesized.…”

“…Therefore, extensive research has been focused on the synthesis of nanostructured MnO 2 as the nanoscale powder, which provides not only a high specific surface area, but also a fast ion and electron transport [16-25]. Various forms of MnO 2 including one-dimensional (nanorods, nanowires, nanobelts, nanotubes) [16-22], two-dimensional [2-D] (nanosheets, nanoflakes) [23-25], and three-dimensional [3-D] (nanospheres, nanoflowers) [26-28] nanostructures have been synthesized. However, the reported specific capacitance values for the various nanostructured MnO 2 electrodes are still far below the theoretical value (approximately 1,370 F/g) [29], which may be attributed to the intrinsically poor electronic conductivity of MnO 2 .…”

A novel microwave absorption material of Ni doped cryptomelane type manganese oxides

“…The first peak is in good agreement with literature reports of 529.3-530.3 for oxides; thus it shows convincing evidence of Mn-O-Mn presence in the undoped products. The second peak can be associated to the hydrated manganese (Mn-O-H) bond [18,20]. Fig.…”