*Article* **Optimized Synthesis Routes of MnOx-ZrO<sup>2</sup> Hybrid Catalysts for Improved Toluene Combustion**

**Xin Huang <sup>1</sup> , Luming Li 2,3,\*, Rong Liu 4,\*, Hongmei Li <sup>2</sup> , Li Lan <sup>5</sup> and Weiqi Zhou <sup>1</sup>**


**Abstract:** In this contribution, the three Mn-Zr catalysts with MnxZr1−xO<sup>2</sup> hybrid phase were synthesized by two-step precipitation route (TP), conventional coprecipitation method (CP) and ball milling process (MP). The components, textural and redox properties of the Mn-Zr hybrid catalysts were studied via XRD, BET, XPS, HR-TEM, H<sup>2</sup> -TPR. Regarding the variation of synthesis routes, the TP and CP routes offer a more obvious advantage in the adjustment of the concentration of MnxZr1−xO<sup>2</sup> solid solution compared to the MP process, which directly commands the content of Mn4+ and oxygen vacancy and lattice oxygen, and thereby leads to the enhanced mobility of reactive oxygen species and catalytic activity for toluene combustion. Moreover, the TP-Mn2Zr3 catalyst with the enriched exposure content of 51.4% for the defective (111) lattice plane of MnxZr1−xO<sup>2</sup> exhibited higher catalytic activity and thermal stability for toluene oxidation than that of the CP-Mn2Zr3 sample with a value of 49.3%. This new observation will provide a new perspective on the design of bimetal catalysts with a higher VOCs combustion abatement.

**Keywords:** Mn-Zr solid solution; toluene; active oxygen; combustion
