Electronic Metal-Support Interactions In Supported Pt-Co?OH?₂/SiO₂ Catalyst

Catalysis is the process of modifying a chemical reaction with the use of a catalyst.This process only works with chemicals that have an existing reaction,and used to accelerate the reaction for commercial purposes.Metal-support interactions play a key role for the catalytic performance of supported metal catalysts.Very recently,a new type of metal-support interactions,the electronic metal-support interaction(EMSI),has attracted increasing attention and opened a new way to tailor the electronic and catalytic properties of supported catalysts.Herein,we demonstrate the EMSI between Pt nanoparticles and Co(OH)2 flakes grown on SiO2,and show its beneficial effect on enhancing the CO oxidation activity.The EMSI characteristics of the Pt-Co(OH)2/SiO2 catalyst are identified by in-situ X-ray absorption fine structure(XAFS),in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and transmission electron microscopy.The main research contents are summarized as follows:(1)To analysis the mechanisms of CO catalytic oxidation,we use incipient wetness impregnation and deposition-precipitation with urea(DPU)to perform the Pt/SiO2 and Pt-Co(OH)2/SiO2 catalyst successively.The morphology and structure of the as-synthesized samples were characterized by TEM,XRD,and HAADF-STEM measurements.Comparison of these samples suggests that the Co(OH)2 flakes play crucial roles in suppressing the Pt aggregation.(2)In order to gain insights into the interactions between Pt and Co(OH)2,we employed the in-situ XAFS and DRIFTS measurements which could afford valuable atomic and electronic information and the surface chemical properties on the catalysts.For Pt-Co(OH)2/SiO2,one more adsorption band peaked at 2063 cm-1 appears in the DRIFTS spectra,the band provides evidence to the negatively charged Pt?-atoms(3)According to the d-band model,the introduction of Co(OH)2 flakes results in an upward shift of the Pt d-band center and strengthens the Pt-CO interaction.On the other hand,the negative charging of Pt atoms broadens the d-band,upshifts the Fermi level,and equivalently,downshifts the d-band center.This leads to more occupancy of the antibonding states of the adsorbed CO,and consequently,weakens the Pt-CO binding strength,enhances catalytic activity.