Abstract
The cooperative catalysis between noble metals and oxygen vacancies in reducible oxides plays an important role in many heterogeneous catalytic reactions, but definite identification of active sites remains challenging. Herein, we report an experimental identification of active sites in HCHO oxidation over TiO2-supported Pt catalysts by means of microscopic and spectroscopic techniques. Pt/TiO2–x catalysts with tunable oxygen vacancy concentrations were designed and fabricated based on hydrogen spillover. A combination of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy allowed us to directly observe the spatial distribution of oxygen vacancies and probe its correlation with the catalytic activity. In situ diffuse reflectance infrared Fourier transform spectroscopy in combination with the online gas chromatography technique was employed to investigate the functionalities of Pt and oxygen vacancies in HCHO oxidation. Our study revealed that HCHO oxidation occurred at the Pt/TiO2–x interface via a cooperative mechanism: oxygen vacancies served as active sites for chemically absorbing HCHO molecules and the adjacent Pt site dissociatively activated O2.
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