Supported platinum catalysts exhibit versatile applications in heterogeneous catalysis while their active sites are identified difficultly due to the structural complexity of solid catalysts. Herein, via a comprehensive microscopic and spectroscopic study using several PtO_x/CeO₂ catalysts with well-controlled CeO₂ morphology, we found that, besides the CeO₂ morphology, the structure of supported platinum species over PtO_x/CeO₂ catalysts is determined by the reaction atmosphere, dominantly forming components of the platinum-ceria solid solution and fine Pt nanoparticles during propane oxidation and preferential oxidation of CO in hydrogen (CO-PROX) reactions, respectively. Catalytic performance of the platinum-ceria catalysts in propane oxidation is tightly associated with the content of metallic Pt sites which is affected by reducibility of platinum-ceria solid solution, whereas the Pt(II) species arising from the Pt-CeO₂ interaction coupling with the surface oxygen vacancy concentration of ceria contribute to the CO reactivity in CO-PROX reaction. There results provide insights into the active sites of platinum-ceria catalysts in both reactions and broadens the concept of morphology-dependent catalysis of oxide-based nanocrystal catalysts that varies with the reactions catalyzed.

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