Mechanism Of Photo-induced Water Oxidation With [Ce?NO₃?₅]^- Into O₂

(NH₄)₂Ce?NO₃?₆?CAN?is commonly used as an oxidant to oxidize water into O₂.It is significant academically for understanding of mechanism of catalytic water oxidation of CAN and for devoleping highly efficient catalysts of water oxidation.The kinetics of photo-induced water oxidation with CAN into O₂ has been investigated under visible light??>400 nm?.The rate of O₂ evolution is the first-order law with respect to the concentration of[Ce?NO₃?5]-:4dc?O₂?/dt =-dc?Ce?NO₃?₅^-?/dt = kc?Ce?NO₃?₅^-?,where the k value is 2.0x10-3 h-1 at 25 ?.Two new peroxide species,[Ce??NO₃?3?O₂?Ce??N03?3]2-and[Ce??NO₃?2?O₂?]-,have been detected by MS/MS mass spectroscopy.The 18O isotope-labelling water oxidation experiment shows that the evolved O₂ originates exclusively from water.The UV-vis and in situ ESR spectra demonstrates the existence of OH·and NO₃· radicals.Based on these results,a more reasonable mechanism of photo-induced water oxidation with[Ce?NO₃?s]-into O₂ has been proposed,in which the formation of NO₃· radicals is considered as the rate-determining step.