Defect engineering to boost charge transfer of Mn-doped γ-Fe₂O₃ hollow porous microspheres via OVFeMn charge channel for efficient photo-Fenton degradation of organics

Fe-based composites exhibit favorable photo-Fenton catalytic performance for environmental remediation, but restricted by high electron hole recombination rate, low reactivity, and instability. Herein, a strategy of mechanical activation-strengthened Mn doping was innovatively proposed to construct Fe 2 O 3 porous microspheres derived from copper slag (CS) base polymers (MA-Mn/CS-Fe 2 O 3 ), and used for highly efficient photo-Fenton degradation of chloromycin hydrochloride (CTC). Benefiting from the collision and shearing of mechanical forces, improved mechanical strength and defect-rich structure were realized in the porous microspheres. Experiments and DFT calculation results reveal that mechanical activation (MA) strengthened Mn to replace the cation vacancy sites and iron ion sites in the octahedron of Fe 2 O 3 , resulting in the formation of rich oxygen vacancies (O V ) and new electronic transmission channels of O V Fe Mn, which act as trapping sites to enhance carrier separation, accelerate the Fe 3 + /Fe 2+ redox cycle, and boost the generation and transformation of reactive oxygen species (ROS). The O V Fe Mn facilitates H 2 O 2 adsorption for its barrierless dissociation into •OH by forming a bridging Mn Fe O O Fe Mn bond. Moreover, the hollow porous structure provides confined space for organic degradation, reduces ROS migration distance, and improves light utilization. These specialties contribute to the superior performance of the MA-Mn/CS-Fe 2 O 3 /Vis/Fenton system for CTC removal (97.3 % within 45 min) in a wide pH range (3 −11), remaining above 93.1 % efficiency after five consecutive cycles. This environmentally-friendly method offers new insights into the harmless treatment and valorization of CS and large-scale production of catalyst.