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

The redox behavior of Y0.05Ce0.1Zr0.85O2 and Y0.1Ce0.1Zr0.8O2 doped with co pper(II) was studied by means of diffuse reflectance electronic spectra (DR ES), temperature-programmed reduction (TPR), and electron paramagnetic reso nance (EPR) techniques. In the absence of copper, it has been demonstrated that the solid is more reducible while it contains more yttrium. The additi on of copper in the form of isolated or clusters/small particles makes the reduction of Ce4+ ions present on the solid surface and in the bulk easier. Nevertheless, three types of Cu2+ ions were evidenced in the solids: isola ted and cluster species in strong dipolar interaction with octahedral symme tries and tetragonal distortion surrounded by more than six ligands, aggreg ates of CuO located on the solid surface, and finally isolated Cu2+ ions lo cated in the solid bulk with octahedral symmetries and strong distortions a nd which remain silent toward reduction by CO.