Reduction effect on cerium oxide catalysts doped with copper( II ) ions. An electron paramagnetic resonance study

The reduction effect on CuCe oxide catalysts with an atomic ratio Cu : Ce = 0.01 has been studied mainly by EPR techniques. The surface species of copper(II) ion pairs and their precursors (Cu2+ ion monomers) were easily reducible by H2, C2H4 and CO. A bronze-like complex (HxCuCeO2) has been obtained before the beginning of the effective reduction of Cu2+ by heating the solid in the presence of hydrogen or ethene. Ce3+ ions have been evidenced near the solid surface during the reduction. By adsorption of CO molecules, CO–2 radicals have been formed on the catalyst surface.