Composition-dependent PMS activation in SrxLa2-xCoO4±δ perovskite-derivatives: From radical to strengthen the electron-transfer pathway

Ruddlesden-Popper phases (R-P) with the chemical formula SrxLa2-xCoO4±δ (x=0.6, 0.8, 1.0, 1.2, and 1.5), consisting of alternating layers of perovskite and rock-salt type oxides, were found to be efficient catalysts for peroxymonosulfate (PMS) activation. By modifying the strontium content, it is possible to tune the spin state of cobalt in the material, which in turn affects the PMS activation mechanism. When the rock-salt layer is intercalated in the R-P perovskite structure, as in Sr0.8La1.2CoO4, a non-radical pathway is involved, which exhibits superior performance in PMS activation, as indicated by the higher reaction rate constant (0.70 min−1) compared to LaCoO3 (0.13 min−1) with SO4•- generation as the primary mechanism. This research provides a deeper understanding of how the electronic structure of cobalt in perovskite oxides influences the PMS activation mechanism. Such insights are crucial for the rational design of effective PMS activators for water treatment.