Redox behaviour of nanoscale ACe₂(PO₄)₃ (A = NH⁺₄, K⁺, Rb⁺) double ceric phosphates

A comparative study of the redox behaviour of nanocrystalline isostructural ACe₂(PO₄)₃ (A = NH⁺₄, K⁺, Rb⁺) double ceric phosphates was performed. It has been established that with respect to alkylperoxyl radicals or hydrogen peroxide as reactive oxygen species, all the double ceric phosphates acted as antioxidants or prooxidants, respectively. The antioxidant activity towards alkylperoxyl radicals was found to be the higher for the phosphates containing potassium or rubidium. Notably, for KCe₂(PO₄)₃ and RbCe₂(PO₄)₃ an inverse dependence of catalytic activity on concentration in the reaction with H₂O₂ was found, in contrast to NH₄Ce₂(PO₄)₃. The redox behaviour of nanoscale cerium dioxide used for comparison was similar to that of ammonium ceric phosphate, but significantly lower in absolute values. This was explained by the suppressive effect of phosphate anions presented in the buffer solutions.

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