Redox behavior of ceria-zirconia solid solutions modified by the chemical filing process

In the ceria-zirconia system, two kinds of preparation methods using oxalic acid or hydrazine monohydrate have been investigated to improve oxygen rel ease and storage properties at low temperatures. These processes consist of a reduction process and surface modification. The redcutants were carbon p articles produced by thermal decomposition of oxalate or a mixture of hydra zine and hydrogen produced by decomposition of hydrazine monohydrate, and t he surface modification was carried out by the calcination of the obtained powders with ammonium chloride in air at 1273 K for 1 h. Cerium and zirconi um chlorides produced on the surface of the solid solutions vaporized to fo rm a chemically filed surface. As a result of the treatment, the ceria-zirc onia solid solutions released a larger amount of oxygen at lower temperatur es. The oxygen storage capacity of the samples measured by a pulse techniqu e also increased after the treatment. The redox properties of the chemicall y filed samples have been maintained even after reduction and reoxidation a ging at 1273 K for many times, indicating thermal durability of the redox a ctivity of the catalysts.