An attractive opportunity to anchor “single - atom” catalysts (SACs) on oxide supports is by using defect sites. By engineering the anchoring sites for supporting SACs, one can alter their electronic and atomic structures which, in turn, define their activity, selectivity, and stability for catalytic reactions. In order to create and tune unique sites for Pt SACs on CeO2 support, we synthesized a system consisting of CeO2 decorated on TiO2 nano-oxides for supporting the Pt SACs. Our hypothesis was that sites near or at the CeO2-TiO2 interface may impart new electronic, structural and catalytic properties on Pt single atoms. To determine the placement of Pt atoms (they can be located either on the surface of nanosized CeO2, or at the interface between nanosized CeO2 and TiO2, or at the surface of TiO2, or in a combination of these possibilities) with the change of Pt weight loadings, we combine multiple structural characterization methods including diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The combined experimental results are also used to characterize the distribution of charge states of single atoms and evaluate the heterogeneity of their binding sites. We found that the position of single atoms can be tuned on a mixed oxide surface by changing the weight loading of single atoms (Fig. 1). We expect the phenomena observed in this work can be also extended to other single atom systems for designing highly efficient catalytic systems.

Tunable placement of Pt “single atoms” on mixed CeO2-TiO2 support

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