Double redox couples manganese oxide nanorods with tunable oxygen defects and their catalytic combustion properties

The activation process of oxygen is a key step for catalytic oxidation reaction. To accelerate the activation of oxygen, tris-valences manganese oxides with two redox couples of Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ were constructed. The introduction of Zn promoted an enhanced Mn³⁺/(Mn²⁺+Mn³⁺+Mn⁴⁺) ratio and then produced an appropriate stoichiometric compositions for the Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. The results indicate that oxygen vacancies, as a significant influence factor for catalytic oxidation, heavily rely on the Mn³⁺ content of the resultant samples. Based on the double redox couples with suitable stoichiometry, the metal ion modified tris-valences manganese oxides presented an enhanced oxygen vacancies content and a better catalytic performance for toluene oxidation compared with the unmodified sample. This study offers a promising route to construct the manganese oxides with two redox couples synchronously with an enhanced Mn³⁺/(Mn²⁺+Mn³⁺+Mn⁴⁺) ratio and oxygen vacancies, resulting in a decreased activating temperature and an increased catalytic performance.

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