Partially amorphization induced S-scheme charge migration in g-C3N4/ Mn 1.1 Fe1.9 O4 defective heterojunction for boosting fenton-like degradation of tetracycline under visible light

S-scheme photo-Fenton catalyst is promising in water purification, whereas its rational design and carrier transfer mechanism remain a challenge. Here, a novel defective heterojunction via combining g-C3N4 3 N 4 with amorphous/crystalline Mn 1.1 Fe 1.9 O 4 (Mn1.1Fe1.9O4-a/c) 1.1 Fe 1.9 O 4- a/c) is fabricated for the degradation of tetracycline. The rich oxygen defects introduced by partially amorphization strategy can regulate the work function of Mn1.1Fe1.9O4-a/ 1.1 Fe 1.9 O 4- a/ c, and switch the charge transfer path of g-C3N4/Mn1.1Fe1.9O4 3 N 4 /Mn 1.1 Fe 1.9 O 4 from type-II to S-scheme, which demonstrates by ultraviolet photoelectron spectroscopy, in-situ kelvin probe force microscopy and density functional theory calculations. Driven by internal electron field, photogenerated electrons can transfer from Mn1.1Fe1.9O4-a/c 1.1 Fe 1.9 O 4-a/c to gC3N4, 3 N 4 , which accelerated the separation of photoexcited carriers and H2O2 2 O 2 activation. Benefiting from the accelerated redox conversion with the action of bimetallic sites, oxygen defects and electrons, the g-C3N4/ 3 N 4 / Mn1.1Fe1.9O4-a/c 1.1 Fe 1.9 O 4- a/c photocatalyst achieves 94.7 % tetracycline removal within 60 min, and the normalized kinetic rate exceeds reported works by 1-2 orders of magnitude. Multiple synergistic pathways lead to more reactive oxygen species generation, which achieves efficient mineralization of tetracycline (79.9 %). This work provides a simple partially amorphization strategy to switch charge transfer pathway from type-II to S-scheme for efficient water purification.