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Enhanced Reducibility of $Ce_1-_xTi_xO_2$ Compared to That of $CeO_2$ and Higher Redox Catalytic Activity of $Ce _1_-_x_-_yTi_xPt_yO_2_-_\delta$ Compared to That of $Ce_1_-_xPt_xO_2_-_\delta$

Baidya, Tinuku and Gayen, Arup and Hegde, MS and Ravishankar, N and Dupont, Loic (2006) Enhanced Reducibility of $Ce_1-_xTi_xO_2$ Compared to That of $CeO_2$ and Higher Redox Catalytic Activity of $Ce _1_-_x_-_yTi_xPt_yO_2_-_\delta$ Compared to That of $Ce_1_-_xPt_xO_2_-_\delta$. In: The Journal of Physical Chemistry B, 110 (11). pp. 5262-5272.

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Abstract

Nanocrystalline $Ce_1_-_xTi_xO_2$ $(0\lex\le0.4)$ and $Ce_1 _-_x_-_yTi_xPt_yO_2_-\delta$ (x = 0.15, y = 0.01, 0.02) solid solutions crystallizing in fluorite structure have been prepared by a single step solution combustion method. Temperature programmed reduction and XPS study of $Ce_1_-_xTi_xO_2 (x = 0.0-04)$ show complete reduction of $Ti ^4^+$ to $Ti^3^+$ and reduction of ~20 $Ce^4^+ to Ce^3^+$ state compared to 8% $Ce_4_+ to Ce_3_+$ in the case of pure $CeO_2$ below 675°C. The substitution of Ti ions in CeO2 enhances the reducibility of $CeO_2. Ce_0_._8_4Ti_0_._1_5Pt_0_._0_1O_2_-_\delta$ crystallizes in fluorite structure and Pt is ionically substituted with 2+ and 4+ oxidation states. The H/Pt atomic ratio at 30 °C over $Ce_0_._8_4Ti_0_._1_5Pt_0_._0_1_O_2_-_\delta$ is 5 and that over $Ce_0_._9_9Pt_0_._0_1O_2_-_\delta$ is 4 against just 0.078 for 8 nm Pt metalparticles. Carbon monoxide and hydrocarbon oxidation activity are much higher over $Ce_1_-_x_-_yTi_xPt_yO_2 (x = 0.15, y = 0.01, 0.02)$ compared to $Ce_1-_xPt_xO_2 (x = 0.01, 0.02)$. Synergistic involvement of $Pt^2^+/Pt^\AA$ and $Ti^4^+/Ti^3^+$ redox couples in addition to $Ce^4^+/Ce^3^+$ due to the overlap of Pt(5d), Ti(3d), and Ce(4f) bands near $E_F$ is shown to be responsible for improved redox property and higher catalytic activity.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 10 Jan 2007
Last Modified: 19 Sep 2010 04:25
URI: http://eprints.iisc.ernet.in/id/eprint/6323

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