Degradation of metronidazole by activating peroxymonosulfate using Z-scheme heterojunction photocatalysts of Co₃O₄/NiCo₂O₄ double shell nanocages under visible light

In this study, ZIF-67 derived Co₃O₄/NiCo₂O₄ double shell nanocages (DSNCs) were fabricated and utilized to degrade metronidazole (MNZ) by activating peroxymonosulfate (PMS) under visible light. The Co₃O₄/NiCo₂O₄-3 (C/N-3) degrade 99.9 % of MNZ by activating PMS under visible light within 20 min, which showed excellent catalytic performance. The double shell nanocage structure effectively reduces the penetration loss of incident light, and the multiple refractions inside the shell effectively enhance the light trapping ability. C/N-3 demonstrates enhanced light absorption capacity, facilitating increased excitation of ground-state electrons to improve catalytic efficiency. Additionally, C/N-3 degrade MNZ well across a wide pH range (3−11) by activating PMS under visible light. The degradation kinetic constant of 0.234 min⁻¹ for the C/N-3/PMS/Vis system was 29.25 and 2.21 times higher than those of Co₃O₄ and NiCo₂O₄, respectively. Furthermore, C/N-3 showed excellent stability through five successive degradation cycle experiments (more than 85.3 %). In summary, the C/N-3 photocatalysts provide valuable insights into water pollution treatment by activating PMS under visible light.