The Origin of Synergetic Effect in Mixed Mn-Co Oxide with Spinel Structure for Catalytic Oxidation of CO
In this work, the origin of the synergetic effect in mixed Mn<sub>x</sub>Co<sub>3-x</sub>O<sub>4</sub> oxides with the spinel structure in the CO oxidation reaction was tested. A series of Mn<sub>x</sub>Co<sub>3-x</sub> oxide catalysts were...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Inorganics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2304-6740/13/1/8 |
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| Summary: | In this work, the origin of the synergetic effect in mixed Mn<sub>x</sub>Co<sub>3-x</sub>O<sub>4</sub> oxides with the spinel structure in the CO oxidation reaction was tested. A series of Mn<sub>x</sub>Co<sub>3-x</sub> oxide catalysts were synthesized by the coprecipitation method with further calcination at 600 °C and varying manganese content from x = 0 to x = 3. The catalysts were characterized using XRD, TEM, N<sub>2</sub> adsorption, TPR, EXAFS, and XPS. The catalytic activity of Mn<sub>x</sub>Co<sub>3-x</sub> oxide catalysts was tested in CO oxidation reactions. The addition of manganese to cobalt oxide results in the formation of mixed Mn-Co oxides based on a cubic or tetragonal spinel structure, a change in microstructural properties, such as surface area and crystal size, as well as local distortions and a decrease in the surface concentration of Co ions and Co in the octahedral sites in spinel structure; it also decreases catalyst reducibility. For all catalysts, the activity of CO oxidation decreases as follows: Mn<sub>0.1</sub>Co<sub>2.9</sub> > Co<sub>3</sub>O<sub>4</sub>~Mn<sub>0.3</sub>Co<sub>2.7</sub> > Mn<sub>0.5</sub>Co<sub>2.5</sub> > MnO<sub>x</sub> > Mn<sub>0.7</sub>Co<sub>2.3</sub> > Mn<sub>0.9</sub>Co<sub>2.1</sub>~Mn<sub>1.1</sub>Co<sub>1.9</sub>~Mn<sub>2.5</sub>Co<sub>0.5</sub> > Mn<sub>2.9</sub>Co<sub>0.1</sub> > Mn<sub>1.7</sub>Co<sub>1.3</sub> > Mn<sub>2.1</sub>Co<sub>0.9</sub> > Mn<sub>1.3</sub>Co<sub>1.7</sub>~Mn<sub>1.5</sub>Co<sub>1.5</sub>~Mn<sub>2.3</sub>Co<sub>0.7</sub>. The Mn<sub>0.1</sub>Co<sub>2.9</sub> catalyst displays the best catalytic activity, which is attributed to its small crystal size and the maximum surface ratio between Co<sup>3+</sup> and Co<sup>2+</sup>. A further increase in the manganese content (x > 0.3) provokes drastic changes in the catalytic properties due to a decrease in the cobalt content on the surface and in the volume of mixed oxide, changes in the oxidation states of cations, and structure transformation. |
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| ISSN: | 2304-6740 |