Construction of K-doped g-C3N5/oxygen vacancies-rich Co3O4 Z-Scheme heterojunction for efficient photo-Fenton elimination of antibiotics

Herein, a ZIF-67-derived oxygen vacancies-rich Co 3 O 4 was supported on molten salt-modified g-C 3 N 5 (KCN) via a precipitation-calcination method. The obtained KCN/O v -Co 3 O 4 composite (the optimized CNCO-3) exhibits excellent catalytic activity in the photo-Fenton system under visible-light irradiation, achieving a degradation efficiency of 96.4% for tetracycline (TC) within 90 min. The reaction rate constant of CNCO-3 composite is 3.5 and 7.5 times higher than that of KCN and O v -Co 3 O 4 , respectively, along with good cyclic stability and high activity in dealing with complex water matrices. The significant improvement in catalytic activity of CNCO-3 is primarily attributed to the formation of a Z-scheme heterojunction between KCN and Ov-Co₃O₄ and the presence of abundant oxygen vacancies, which collectively promote photogenerated carrier separation, accelerate the Co²⁺/Co³⁺ redox cycle, and improve visible-light absorption. Importantly, in-situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations confirmed that KCN and O v -Co 3 O 4 form a Z-Scheme heterojunction, which enhances the separation and migration of photogenerated carriers and accelerated the Co 2+ /Co 3+ redox cycle. Superoxide radicals (•O 2 - ) have been confirmed to be the main reactive oxygen species produced in the photo-Fenton process. A novel Z-Scheme heterojunction consisting of K-doped C 3 N 5 and oxygen vacancy-rich Co 3 O 4 was prepared. KCN/O v -Co 3 O 4 composite exhibited superior photocatalytic H 2 O 2 activation for tetracycline (TC) degradation. Superoxide radicals (•O 2 - ) were the main active oxygen species dominating TC degradation. The transfer of photogenerated electrons from KCN to O v -Co 3 O 4 follows the Z-Scheme mechanism. • A novel Z-Scheme heterojunction consisting of K-doped C 3 N 5 and oxygen vacancy-rich Co 3 O 4 was prepared. • KCN/O v -Co 3 O 4 composite exhibited superior photocatalytic H 2 O 2 activation for tetracycline (TC) degradation. • Superoxide radicals (•O 2 - ) were the main active oxygen species dominating the TC degradation. • The transfer of photogenerated electrons from KCN to O v -Co 3 O 4 follows the Z-Scheme mechanism.