Photoinduced oxidative transformation of diphenylamine on CeO2

On the surface of CeO2, diphenylamine (DPA) in ethanol undergoes a photoinduced oxidative transformation yielding N-phenyl-p-benzoquinoneimine (PBQ). The photoinduced transformation of DPA on CeO2 was enhanced by increasing the (i) [DPA], (ii) CeO2-loading, (iii) airflow rate and (iv) photon flux. The formation of PBQ on the CeO2 surface increased due to irradiation at 254 nm compared to that observed from irradiation at 365 nm. The activity of the CeO2 surface does not decrease during reuse. The photoinduced oxidative transformation mechanism was discussed, and the kinetic law was determined. ZnO and ZnS enhance the photoinduced transformation indicating interparticle charge transfer in semiconductor mixtures.