The activation of MnOx-ZrO2 catalyst in CO oxidation: Operando XRD study

•The MnOx-ZrO2 catalyst structure is stable under catalytic reaction of CO oxidation.•The reduction–oxidation pretreatment leads to an increase in the catalytic activity.•Pretreatment leads to decomposition of a solid solution and growth of oxide dispersion. The present study demonstrates that the reduction–oxidation pretreatment leads to an increase in the catalytic activity in CO oxidation for MnOx-ZrO2 catalyst. Crystalline phases present in as-prepared MnOx-ZrO2 catalyst are Mn3O4, Mn2O3 and solid solution (Mn,Zr)O2. By varying the conditions of pretreatment, the following results can be achieved: (1) decomposition of a solid solution; (2) change the ratio and the dispersion of oxides. In CO environment, the reduction of Mn cations occurs both in the volume of the (Mn,Zr)O2 solid solution and in manganese oxides. The reduction process is accompanied by the MnO segregation on the surface of the initial oxides. In an oxygen-containing environment, the reoxidation of surface manganese oxides proceeds with the formation of Mn2O3 and Mn3O4.