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The metal-support interaction in the system of platinum supported on titanium oxides of different crystalline structures was investigated. Titanium oxide powders used as supports were prepared by neutralization of TiOCl2-analogue solution with either NaOH or NH3 base at varied pH. Pt was introduced onto the supports by impregnation. The phenomenon of strong metal-support interaction (SMSI) was determined by the suppression of chemisorption of H2 over samples reduced at 773 K, in comparison with the behavior of samples reduced at 473 K. The loss of adsorption capacity was proved not due to metal sintering by examining the recovery of adsorption capacity after reduction, reoxidation and reduction cycle, accompanied with examination of the size of Pt particle with an x-ray diffractiometer and a transmission-electron microscope. The results showed that SMSI phenomenon was common to Pt supported on titanium oxides of all the varied crystalline structures. However, the chemisorption capacity of Pt reduced at 473 K varied greatly with the sodium content in the supports, which in turns affects the crystalline structure of titanium oxide. These results are attributed mainly to electronic effect endowed by the support. |
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