Co3O4 with the Enhancement of Peroxymonosulfate Adsorption Capacity by Rare Earth Europium-Doping for High-Efficiency Organic Dye Degradation

Cobalt-based metal–organic framework (MOFs)-derived catalysts are acknowledged for their effectiveness in activating peroxymonosulfate (PMS) for the treatment of persistent pollutants. However, the limited adsorption of PMS on the catalyst surface markedly reduces its degradation efficiency. To overcome this limitation, nanoflower-like Eu2O3/Co3O4-0.3 catalysts were successfully fabricated by incorporating europium (Eu) into cobalt-based MOF via the hydrothermal and calcination techniques. The doping of Eu not only enhances the adsorption of more PMS on the catalyst's surface but also serves as an electron transfer mediator to regulate the Co2+/Co3+ redox cycle and promote the generation of oxygen vacancies (OV). The catalyst Eu2O3/Co3O4-0.3 was used to activate PMS for the degradation of rhodamine B (RhB), and it was found that the degradation rate constant (k) of the Eu2O3/Co3O4-0.3/PMS system was approximately 8 times higher than that of the Co3O4/PMS system, achieving complete degradation within 20 min. Furthermore, Eu2O3/Co3O4-0.3 exhibited excellent mineralization capacity, stability, and recyclability. Trapping experiments indicated that singlet oxygen (1O2) is the primary active species, suggesting that this material is applicable in complex aqueous environments. Density Functional Theory (DFT) calculations revealed that the adsorption energy (Eads) of PMS on the Eu2O3 surface is −4.05 eV, which is much greater than that on Co3O4 (Eads = −0.32 eV). This study provides a new method for designing nonhomogeneous catalysts to activate PMS for efficient degradation of pollutants.