Charge transfer and PMS activation in high-entropy spinel oxide-based Z-scheme heterojunctions for ciprofloxacin degradation

The low charge transfer and separation efficiency of high-entropy oxides remain the urgent problems that need to be solved to limit their application in the field of photocatalysis. A low-temperature sintering technology combined with polyacrylamide gel method was used to synthesis a series of Z-scheme heterojunctions (Ni 0.2 Zn 0.2 Mg 0.2 Cu 0.2 Co 0.2 )[Al 0.9 (Cr 0.025 Fe 0.025 Mn 0.025 Co 0.025 )] 2 O 4 /photinia leaves (A/Ps) with the diverse mass percentages of A/Ps, namely 9:1 (S1), 8:2 (S2), and 7:3 (S3) to enhance the photocatalytic activity of high-entropy oxides. The C element in Ps, the continuous reaction of various multivalent metals, and the electron transfer pathway are conducive to the available active Peroxomonosulfate (PMS). The degradation percentage of Ciprofloxacin (CIP) by S3/PMS/vis reaches 82.6% within 20 min, surpassing the Ps/vis, A/vis and S3/vis for 5.39, 2.07 and 2.96 times, respectively. The S3/PMS/vis exhibits high charge transfer and separation efficiency, excellent cyclic and structural stability, which is suitable for diverse environmental conditions, and demonstrates a remarkable degradation percentage. Density functional theory (DFT) is employed to investigate the variation of adsorption energy in different catalysis systems. The degradation pathway and ecotoxicity of CIP are assessed to confirm the effective degradation of CIP by S3/PMS/vis and emphasize that the charge transfer and photo-activation PMS are effective strategies for removing pollutants from natural water bodies. • A novel high-entropy spinel oxide based Z-scheme heterojunction was fabricated. • The catalysts exhibit high catalytic activity for the degradation of CIP under the synergistic action of PMS activation and simulated sunlight. • The adsorption energy of A and Ps and PMS were calculated. • The free and non-free radical pathways and Z-scheme catalytic mechanism were proposed.