Redox behavior of Y0.05Ce0.1Zr0.85O2 and Y0.1Ce0.1Zr0.8O2 system catalysts doped with copper(II)

The redox behavior of Y 0.05 Ce 0.1 Zr 0.85 O 2 and Y 0.1 Ce 0.1 Zr 0.8 O 2 doped with copper(II) was studied by means of diffuse reflectance electronic spectra (DRES), temperature-programmed reduction (TPR), and electron paramagnetic resonance (EPR) techniques. In the absence of copper, it has been demonstrated that the solid is more reducible while it contains more yttrium. The addition of copper in the form of isolated or clusters/small particles makes the reduction of Ce 4+ ions present on the solid surface and in the bulk easier. Nevertheless, three types of Cu 2+ ions were evidenced in the solids: isolated and cluster species in strong dipolar interaction with octahedral symmetries and tetragonal distortion surrounded by more than six ligands, aggregates of CuO located on the solid surface, and finally isolated Cu 2+ ions located in the solid bulk with octahedral symmetries and strong distortions and which remain silent toward reduction by CO.