Abstract

Electron paramagnetic resonance (EPR) has been used to study the effect of heat treatment under air or hydrogen on the behaviour of CuCe oxide catalysts. Monomers, dimers and clusters of Cu 2+ ions have been detected in CeO 2 after different calcination temperatures. Monomers and dimers are located in specific and similar sites of the ceria lattice in place of Ce 4+ ions. When two Cu 2+ ions are situated at a distance of 3.6 ± 0.3 Å and bridged by an oxygen, the dimer signal is formed. The reduction of dimers by hydrogen gives monomers in a first step and these transform into Cu − or Cu 0 species in a second step.

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