CeO2ZrO2 solid solutions
containing 10-66 mol% ZrO2 have been
formed by milling CeO2 powder in ethanol
with a number of ZrO2 balls using the
high-energy ball milling apparatus under wet conditions.
The oxygen storage capacity (OSC) of Pt/CeO2ZrO2
catalyst composed of 1wt% Pt and the formed CeO2ZrO2
solid solutions as a support increased in propotion
to ZrO2 content at 500°C, and its maximum OSC (420μmol-O2/gjwas
obtained with 40 mol% ZrO2 content.
The value of the OSC was nearly constant regardless
of the ZrO2 content above 40 mol%.
Heating the mixture of CeO2 powder
and a precipitate formed by the reaction of ZrO(NO3)2
aqueous solution with ammonia solution at 1200°C under reducing conditions, followed by heating
at 500°C under oxidizing
conditions, CeO2ZrO2 solid
solutions containing 30-80 mol% ZrO2
have been synthesized. The OSC of Pt/CeO2ZrO2
catalyst composed of 1wt% Pt and the synthesized
CeO2ZrO2 solid solutions
increased in propotion to ZrO2 content
at 500°C, and its maximum
OSC (825μmol-O2/g)
was obtained with 50 mol% ZrO2 content.
The value of 825μmol-O2/g
OSC corresponds to the reduction to Ce3+
of 97.4% Ce4+ initially present. On
the other hand, the value of the OSC decreased
in inverse propotion to ZrO2 content
above 50 mol%.
The reason why the value of the maximum OSC of
the latter (825μmol-O2/g)
is higher than that of the former (420 μmol-O2/g)
is thought to be because most of the Zr4+
in the cationic sites of CeO2ZrO2
solid solution of the latter are well-ordered
in the lattice of the solid solution than that
of the former.
The OSC by unit of Ce of Pt/CeO2ZrO2
catalyst composed of 1wt% Pt and CeO2ZrO2
solid solution with 50 mol% ZrO2 increased
in propotion to ZrO2 content at temperatures
of 300-700°C.
