**5. Conclusions**

In this paper, a series of Mn-Zr catalysts with different Mn/Zr ratios were successfully prepared via co-precipitation and improved co-precipitation routes, and their catalytic performance for toluene combustion was evaluated. It was found that the TP-Mn2Zr3 catalyst possesses the lowest T<sup>50</sup> and T<sup>90</sup> temperature at 263 and 269 ◦C and exhibits practical cycle stability. Moreover, the relationship between the catalyst performance and texture was deeply investigated via some characterization techniques, including XRD, HRTEM, BET, H2-TPR, and XPS. The results showed that the doping of Mn enables the crystal structure of ZrO<sup>2</sup> to transform from the monoclinic to the cubic phase, exposes the stable c-ZrO<sup>2</sup> (111) phase, and increases the specific surface area of Mn-Zr bimetal catalysts via the co-precipitation strategy. In particular, the optimized co-precipitation process enriches more exposure of the defective (111) surface of the MnxZr1-xO<sup>2</sup> solid solution to active oxygen molecular and more oxygen vacancy as well as the higher concentration of Mn4+, which is conducive to the mobility of oxygen to improve their catalytic activity for toluene combustion. This new observation will provide a promising strategy to design excellent catalysts for VOCs abatement.

**Author Contributions:** X.H.: completing the experiments and writing—original manuscript. L.L. (Luming Li): project administration, providing the experiment ideas, and writing—review. R.L., H.L., L.L. (Li Lan) and W.Z.: analysis and agree to take responsibility for the accuracy and authenticity of the research work. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Open Fund of the Key Laboratory of Coarse Cereal Processing, Ministry of Agriculture and Rural Affairs, Sichuan Engineering and Technology Research Center of Coarse Cereal Industrialization (2020CC020).

**Data Availability Statement:** The data of this research is available within the manuscript.

**Acknowledgments:** We are grateful to the experimental platform provided by the Institute of Environmental Catalysis and Dust Treatment of Chengdu University. Thanks to the TEM characterization provided from Xiamen University and the XPS analyzed provided by Institute for Advanced Study of Chengdu University.

**Conflicts of Interest:** The authors declare no conflict of interest.
