Abstract: Perovskite oxides, with an ABO3 general formula, have attracted much attention as effective peroxymonosulfate (PMS) activators because of their composition adjustability and chemical stability. A doping strategy has been applied to enhance the PMS activation capability with the modulation of the crystal structure of the parent LaCoO3-d perovskite by substituting Co atoms located at the B-site, with high valence state transition metals. Herein, a series of LaCo1-xMoxO3-d perovskites were prepared with different Mo content, showing a phase transformation from rhombohedral to cubic-like structures. LaCo0.95Mo0.05O3-d compound is located at the so-called morphotropic phase boundary (MPB) boosting PMS activation performance as well as enhanced stability. The presence of local inhomogeneities, observed as oxygen vacancies, has been detected in the MPB region enhancing the catalytic effect of pollutant degradation. Mo doping induced Co reduction that contributed to the enhanced PMS activation. Sulfate radical was identified to be the dominating reactive specie for LaCo1-xMoxO3-d catalyzed PMS activation. This work contributes first, to clarifying the role of Mo doping to boost PMS activation, and second to highlighting the crucial role of the reduced oxidation state as well as the oxygen vacancies in the MPB for PMS activation. Impressive results were obtained when LaCo0.95Mo0.05O3-d compound was deposited in a Lab-grade photoreactor with LED technology, reaching a complete removal of paracetamol in the first minute. This study provided new insight into the rational design of PMS activator and developed a new strategy for heterogeneous active PMS at a photoreactor with immobilized catalysts.

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