Adsorption and activation of CO2 on Pt/CeOx/TiO2(110): Role of the Pt-CeOx interface

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• Strong electronic perturbations for Pt on CeO x /TiO 2 (110). • CO 2 binds extremely well to Pt/CeOx/TiO 2 (110). • CO 2 molecular structure changes to that of CO 2 − . • CO, CH x , C and CO 3 are generated by CO 2 decomposition. The adsorption and dissociation of CO 2 on TiO 2 (110), CeO x /TiO 2 (110) and Pt/CeO x /TiO 2 (110) surfaces has been examined using Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS). The substrates under study exhibited different degrees of complexity which were tested for the binding of the adsorbate and the cleavage of C-O bonds. The surfaces were prepared by depositing CeO x (0.1 ML) onto TiO 2 (110) to form a mixed oxide support, onto which Pt nanoparticles (0.2 ML) were deposited. This configuration yields a complex set of interfaces between metal and oxides and we have systematically titrated the active role of each component (Pt 4f, Ce 3d and Ti 2p regions) and the arising surface intermediates (C 1 s and O 1 s regions). CO 2 barely bonds to stoichiometric TiO 2 (110). It heals oxygen vacancies of this oxide surface (CO 2,gas → CO gas + O a ) and does not form stable carbonates. A stable carbonate was seen upon adsorption of CO 2 on CeO x /TiO 2 (110) and on this type of substrate the adsorbate also removed O vacancies leading to the oxidation of Ti 3+ and Ce 3+ sites. Pt nanoparticles dispersed on CeO x /TiO 2 (110) were highly effective for the binding and dissociation of CO 2 , with the formation of CO 3 , CO, C and CH x species on the Pt/CeO x /TiO 2 (110) system. The results of theoretical calculations based on density-functional theory (DFT) show that Pt/CeO x /TiO 2 (110) binds CO 2 much stronger than surfaces of bulk platinum {(111), (100), (110)} or other late transition metals. On a Pt-CeO x interface, the molecule adsorbs with a bent configuration (~130° O-C-O bond angle) and with a substantial elongation (~ 0.1 Å) of the C-O bonds, facilitating its transformation into high value chemicals.