Electron Paramagnetic Resonance Study of La Cuprate-based Catalysts for Phenol Oxidation

A set of six La2-xEuxCuO4+δ samples, with x ranging from 0 to 1.33 have been analysed by EPR spectroscopy and X-ray diffractometry, to obtain information on their structure and on the change brought about by their use as catalysts for phenol oxidation with hydrogen peroxide. With increasing Eu content, a transformation of the orthorhombic structure of the La cuprate (x = 0) parent compound into two different TLa and T′Eu tetragonal structures takes place, accompanied by a change of electrical conductivity and the appearance of particular features in the EPR spectrum. The latter was a most sensitive probe for monitoring the structural modification arising during the catalytic reaction, even during the very early stages when the XRD pattern does not yet show any significant change.