Enhanced reducibility of Ce<SUB>1-x</SUB>Ti<SUB>x</SUB>O<SUB>2</SUB> compared to that of CeO<SUB>2</SUB> and higher redox catalytic activity of Ce<SUB>1-x-y</SUB>Ti<SUB>x</SUB>Pt<SUB>y</SUB>O<SUB>2-&#948;</SUB> compared to that of Ce<SUB>1-x</SUB>Pt<SUB>x</SUB>O<SUB>2-&#948;</SUB>

Nanocrystalline Ce1-xTixO2 (0 = x = 0.4) and Ce1-x-yTixPtyO2-&#948; (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 Ce1-xTixO2 (x = 0.0-04) show complete reduction of Ti4+ to Ti3+ and reduction of 20% Ce4+ to Ce3+ state compared to 8% Ce4+ to Ce3+ in the case of pure CeO2 below 675 &#176;C. The substitution of Ti ions in CeO2 enhances the reducibility of CeO2. Ce0.84Ti0.15Pt0.01O2-&#948; crystallizes in fluorite structure and Pt is ionically substituted with 2+ and 4+ oxidation states. The H/Pt atomic ratio at 30 &#176;C over Ce0.84Ti0.15Pt0.01O2-&#948; is 5 and that over Ce0.99Pt0.01O2-&#948; is 4 against just 0.078 for 8 nm Pt metal particles. Carbon monoxide and hydrocarbon oxidation activity are much higher over Ce1-x-yTixPtyO2 (x = 0.15, y = 0.01, 0.02) compared to Ce1-xPtxO2 (x = 0.01, 0.02). Synergistic involvement of Pt2+/Pt&#176; and Ti4+/Ti3+ redox couples in addition to Ce4+/Ce3+ due to the overlap of Pt(5d), Ti(3d), and Ce(4f) bands near EF is shown to be responsible for improved redox property and higher catalytic activity