{"title":"Preparation of Mn3O4 nanoparticles on Al-substrate for degradation of Rhodamine B under solar light","authors":"A. Chaa, A. Haddad, G. Rekhila, S. Tria, M. Trari","doi":"10.1007/s13738-024-03054-2","DOIUrl":null,"url":null,"abstract":"<div><p>The semiconducting properties of Mn<sub>3</sub>O<sub>4</sub> thin films were assessed for the heterogeneous photocatalytic oxidation of Rhodamine B (Rh B). The films were grown on Al-substrate using a spray coating, and their physical and photoelectrochemical characteristics were studied. X-ray diffraction analysis showed a well-crystallized structure of the spinel Mn<sub>3</sub>O<sub>4</sub>. The atomic force microscopy revealed dense and irregular grains with a mean size of ~ 50 nm and a thickness of ~ 1 µm. The direct optical transition at 2.19 eV, in agreement with the brown color, is assigned to <i>d–d</i> transitions within the incomplete Mn-3<i>d</i> shell, which enables efficient photocatalytic conversion of the solar radiation. The photoelectrochemical measurements demonstrated <i>p</i>-type comportment, evidenced by a negative slope in the [capacitance<sup>−2</sup>–potential: C<sup>−2</sup>–E] graph with a flat band potential of + 0.35 <i>V</i><sub>SCE</sub> and a hole density of 6.5 × 10<sup>18</sup> cm<sup>−3</sup>. The electrochemical impedance spectroscopy (EIS) plot showed a semicircle due to a capacitive comportment of the bulk spinel (<i>R</i><sub><i>b</i></sub> = 70 kΩ cm<sup>2</sup>). The center positioned below the abscissa axis (− 23°) with a constant phase element (CPE). The conduction band (− 1.64 <i>V</i><sub>SCE</sub>) is more cathodic than the <span>\\({\\text{O}}_{{2}} /{\\text{O}}_{{2}}^{ \\bullet - }\\)</span> level, thus catalyzing the photocatalytic process by <span>\\({\\text{O}}_{{2}}^{ \\bullet - }\\)</span> radicals. Under sunlight, 50% reduction of the Rh B concentration (10 ppm) was achieved within 1 h, the color removal, followed by spectrophotometry obeys a pseudo-first-order kinetic model with a rate constant of 9.9 × 10<sup>–3</sup> min<sup>−1</sup> (<i>t</i><sub>1/2</sub> = 70 min).</p></div>","PeriodicalId":676,"journal":{"name":"Journal of the Iranian Chemical Society","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13738-024-03054-2.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the Iranian Chemical Society","FirstCategoryId":"92","ListUrlMain":"https://link.springer.com/article/10.1007/s13738-024-03054-2","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The semiconducting properties of Mn3O4 thin films were assessed for the heterogeneous photocatalytic oxidation of Rhodamine B (Rh B). The films were grown on Al-substrate using a spray coating, and their physical and photoelectrochemical characteristics were studied. X-ray diffraction analysis showed a well-crystallized structure of the spinel Mn3O4. The atomic force microscopy revealed dense and irregular grains with a mean size of ~ 50 nm and a thickness of ~ 1 µm. The direct optical transition at 2.19 eV, in agreement with the brown color, is assigned to d–d transitions within the incomplete Mn-3d shell, which enables efficient photocatalytic conversion of the solar radiation. The photoelectrochemical measurements demonstrated p-type comportment, evidenced by a negative slope in the [capacitance−2–potential: C−2–E] graph with a flat band potential of + 0.35 VSCE and a hole density of 6.5 × 1018 cm−3. The electrochemical impedance spectroscopy (EIS) plot showed a semicircle due to a capacitive comportment of the bulk spinel (Rb = 70 kΩ cm2). The center positioned below the abscissa axis (− 23°) with a constant phase element (CPE). The conduction band (− 1.64 VSCE) is more cathodic than the \({\text{O}}_{{2}} /{\text{O}}_{{2}}^{ \bullet - }\) level, thus catalyzing the photocatalytic process by \({\text{O}}_{{2}}^{ \bullet - }\) radicals. Under sunlight, 50% reduction of the Rh B concentration (10 ppm) was achieved within 1 h, the color removal, followed by spectrophotometry obeys a pseudo-first-order kinetic model with a rate constant of 9.9 × 10–3 min−1 (t1/2 = 70 min).
期刊介绍:
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